149 64 py 1 Copyright ]J^._ COPYRIGHT DEPOSIT. CHEMISTRY OF THE HOUSEHOLD BY MARGARET E. DODD, S. B. GRADUATE OF MASSACHUSETTS INSTITUTE OF TECHNOLOGY TEACHER OF SCIENCE, WOODARD INSTITUTE CHICAGO AMERICAN SCHOOL OF HOME ECONOMICS 1910 A ^ COPYRIGHT, 1904, 1905, BY AMERICAN SCHOOL OP HOUSEHOLD ECONOMICS COPYRIGHT, 1907, 1910, BY HOM£ ECONOMICS ASSOCIATION CCI,A^61873 CONTENTS Page Water I The Atmosphere ...... . 14 Combustion ....... 20 Fuels . . . . . ' , . 23 Food ........ 29 Sugars and Starches ..... . 32 Digestion ....... 35 Cooking . • . ' 37 Fats 43 Nitrogenous Foods . 45 Cooking of Nitrogenous Food Stuffs 48 Effects of Cooking ..... . 51 Mineral Matter ...... 52 T)ecay ........ . 54 Cleaning . ..... 55 Chemistry of the Laundry .... . 66 Removal of Stains ...... 73 Bleaching . . . . . . 80 Cleaning AA^oodwork « . . . . 84 Cleaning Metals ...... . 85 Chemistry OF Baking Powder . . . 89 Lighting ....... . 92 Lime ....... 102 Chemistry and Electricity .... . 105 Plant Life ....... 108 Chemical Terms, ...... . Ill The Housekeeper's Laboratory 113 Impurities in Water ..... . 127 Laundry Work ...... 129 111 IV CONTENTS Bluing ..... Home Soap Making Dishwashing .... Latent Heat .... Use of the Thermometer Bread Making .... Home Made Baking Powder . Distillation . . . . Composition of Gas Spontaneous Combustion Conservation of Energy Bibliography .... Program of Supplemental Study Index ..... 131 133 135 138 140 141 142 143 144 146 146 149 151 163 o 2 o o u 'Q z <: hj w o H X z w X C ) 10 H TD •— < u (-> (Tj Pi ai s? O c Pi c« s - CHEMISTRY OF THE HOUSEHOLD A Day's Chemistry BEING an outline of the simplest and most evi- dent chemical changes suggested by a day's work at home and a description of the various chemical substances of interest to the housewife. WATER The morning bath will introduce us agreeably to the wonderful chemical substance, water, and with this oc'cun-enc© substance we will begin our study of a day's chemistry. The water for the house may come from the town sup- ply, from wells, cisterns, or springs. It may be ''surface water," from pond, lake, or stream, or it may be "ground water," from wells or deep springs. Cis- tern water is, of course, rain water. Water is present in many substances where we might not suspect it. All living things contain a large percentage of water. Of an athlete weighing 150 pounds, all but about 42 pounds is water. Wood, meat, vegetables, fruit, when dried, weigh from 50 to 98 per cent less. Many natural and artificial substances owe their crystalline form to 2 CHEMISTRY OF THE HOUSEHOLD. water and when heated, give off this "water of crystal- Hzation" and crumble to powder. Common washing soda shows this effect, when exposed to the air, and soon gives off so much water that its crystalline char- acter is lost. Katurai All watcr fouud in nature is more or less impure, ^**®' that is, it contains substances in solution. It dissolves air and takes substances from the soil and rocks over which it runs. Often it comes in contact with animal and vegetable substances and dissolves something from them. Near dwellings the water in streams, ponds, and wells is very likely to become contaminated. De- caying substances give rise to materials easily dissolved in water, which may travel for a considerable distance under ground, so that the drainage from the house or barn is frequently carried to near-by streams or wells, making their waters quite unfit to drink. Fig. I. The following experiment will illustrate that air is dissolved in water. Experiment. Place a tumbler of fresh well-water or tap-water in a warm place. After a time, bubbles will be seen collecting on the sides of the glass. This is air which was dissolved in the water. As the water grows warm, it cannot hold so much air in solution and some of it separates. Distilled Most of the impuritics in water are less easily con- verted into vapor than the water itself; hence, when the water is boiled, they stay behind while the water *'boils away". Water from almost any source can be made pure and clear by distillation. Distilled water is Watet WATER. 3 prepared in an apparatus known as a still. See Fig. 2. A still consists of a boiler, A, and a condenser. In the condenser, a coil of tube, D, usually made of pure FIG. 1. WELL, CONTAMINATED BY HOUSE DRAINAGE. tin, is surrounded by cold water which continually runs through the apparatus. The steam, admitted at the upper end of the coil, is condensed by the low tem- perature and distilled water is collected at the lower CHEMISTRY OF THE HOUSEHOLD. Rain Water end. In the laboratory, distilled water is often made in the glass apparatus shown in Fig. 3. Distilled water has a flat taste, because air and other dissolved substances which give water its taste have been removed. It will again dissolve the air on being ])oured several times from one vessel into another. Rain is water which has been evaporated from the surfaces of natural bodies of water, oceans, lakes, and from the land, and is practically free from mineral matter, but contains dissolved gases. The vapor, cooled at the low temperatures of the upper levels of air, falls as rain. The first fall of any FIG. 2. A STILL. A, Gooseneck; B. Boiler; D, Condensing Coil. shower is mixed with impurities which have been washed from the air. Among these may be carbon dioxide, ammonia, and carbon in the form of soot and creosote. It is these last impurities which cause the WATER. 5 almost indelible stain left when rain water stands upon window-sills or other finished woods. Fii Makiug Distilled Water in the Laboratory. Water is a nearly universal solvent. It dissolves more substances and these in larger quantities than any other liquid. At a given temperature, water will dis- solve only a certain proportion of the various salts and other soluble substances. When the water will take up no more, the solution is said to be saturated. Increasing tlie temperature generally increases the dis- solving power of water for solids and liquids. The reverse is usually true for gases. When a saturated solution of a solid is cooled, crys- tals are frequently formed, many having beautiful shapes. Examples are shown in Fig. 4. Experiiiiciit. In an earthen-ware or enameled dish dissolve as much alum as possible in a little boiling water. Pour the solution into a shallow dish or sau- Solubility 6 CHEMISTRY OF THE HOUSEHOLD. cer, and set it away for a day or more where it will be undisturbed. Beautiful, clear, six-sided crystals will form in the dish. If strings are hung in the solution, the crystals will form upon them. Rock candy crystals are made from cane sugar syrup in this way. The experiment may be repeated, using washing soda instead of alum. iv "> Effect of Water on Metals FIG. 4. SHAPES OF CRYSTALS. Silver, copper, and tin are not perceptibly dissolved in pure water, but when combined with acid substances, the compounds formed are soluble. These compounds of a metal with an acid are called salts. The salts of copper, zinc, and lead are poisonous. Copper, brass, (an alloy of copper with zinc) tin, solder, and iron are metals easily affected by acids, so that cooking utensils made of these materials should not be used with acid substances like lemon and vinegar. WATER. Lead pipes are much used in plumbing, and as a rule no evil results follow, since ordinary drinking water acts under most circumstances only very slight- ly upon lead. The pipes are soon coated with a layer of carbonate and sulphate of lead, which is insoluble and prevents any further action. Water from new lead pipes, or pipes not kept constantly full, or from a hot-water system in which lead is used, should never be used for drinking or cooking because of danger from poisoning. Pure distilled water, or rain water, affects lead more than ordinary ground water. Rain water absorbs more or less carbon dioxide gas from the air and soaking into the soil often comes in contact with magnesia in the rocks and with limestone. Water containing this these gas will dissolve mineral substances mak- ing what is known as ''hard" water, a very dif- ferent substance from the original rain water which is "soft." This subject will be dis- cussed when the chem- istry of the laundry is explained. ter- - ;^:^i W^ ' (^^ Filtered, watev Effect of Water on Lead Hard Water Layer of qr&vel Lay e-r of cK&rco&l Latyev- of gravel FIG. 5. A WATER FILTER. Ordinary water for drinking purposes is often filtered. Filtration will remove small particles suspended in the water, but has no effect on substances dissolved in it. The small charcoal or sand filters will not remove Filteringr of Water 8 CHEMISTRY OF THE HOUSEHOLD. the minute living forms called micro-organisms or germs, some of which are the cause of disease. A filter of porous stone or procelain, in which the water filters slowly, is more effective. A good filter is shown in Figure 5. Water which has strained or filtered through several feet of earth is often much improved, but the earth filter itself may become contaminated after a while and more harm than good result. A thick layer of sand and rock, however, removes germs effectively, and con- sequently water from deep driven wells is safe, iiomposition Water was long considered an elementary or simple substance, but towards the end of the last century it was found to consist of two quite different substances so intimately joined together that the identity of each is lost. If we pass an electric current through water in the proper way, we see a gas rising in bubbles from the end of the wire by which the current enters and a like appearance at the wire by which the current leaves the water. The two gases have evidently come from the water and are the substances out of which it is made for the water begins to disappear. By placing an inverted glass filled with water over each wire, the gases are easily collected. See Fig. 6. When one bottle is full of gas, the other will be only half full; and on decomposing the whole of a given amount of water, this proportion holds true. If we test these gases, we shall find them quite dif- ferent. The bottle which is full contains a gas called WATER, 9 hydrogen. There is evidently twice as much of this by volume in water as of the other gas which is called oxygen. These two gases were tied together by what is known as chemical force, but the electric current separated them and gave us an opportunity to make the acquaintance of each by itself. We would hardly suppose this clear, colorless liquid to be composed of such material. On decomposing pure water from any rs HYDROGEN Fig. 6. Decomposing Water Into Oxygen and Hy- drogen Gas. source, the proportion of oxygen to hydrogen is always the same, and in fact, all chemical compounds have a certain composition which never varies under any con- dition. The name hydrogen comes from two Greek words, meaning water and to produce. Hydrogen is interest^ ing as being the lightest common substance. It is an invisible gas like air, but unlike air will burn. If a Hydrogea 10 CHEMISTRY OF THE HOUSEHOLD. lighted candle be placed in a bottle of hydrogen, the flame will be at once extinguished, though the hydro- gen will take fire at the mouth of the bottle. Fig. 7. Hydrogen will unite with other substances besides oxygen ; that is, it will join with other substances by chemical force. It forms a part of most animal and vegetable substances. Tig. 7. Hydrogen Will Burn iu Air. Fif. 8. A Candle Burns Vigorously in Oxygen. Oxygen Oxygcu, as wcll as hydrogen, is a tasteless, color- less, odorless gas. The weight of a given volume is sixteen times that of the same volume of hydrogen. It is very abundant and the most important substance to mankind. Should we test this gas with a, lighted candle, as we did the hydrogen, we would find that the oxygen would not give a flame, but that the, candle would burn far more vigorously. Fig. 8. WATER. II When substances burn in oxygen they really unite A^ith it chemically, forming new substances called oxides. Water is hydrogen united with oxygen and its chemical name might therefore be oxide of hydrogen. When water is heated in an open vessel, evapora- tion from the surface of the liquid is more rapid as the temperature increases. Soon vapor is formed on the sides and bottom of the vessel and bubbles begin to rise which are at once condensed by the cooler parts of the liquid, thus making the familiar "singing" noise. Finally the liquid becomes so hot that the bubbles reach the surface without condensing, and then the water boils and goes off into the air as steam, an invisible gas. This occupies the small space between the spout of the tea-kettle and the cloud of vapor which is com- monly called steam, but is really finely divided drops of water. A cubic inch of water makes about a cubic foot of steam. The temperature at which pure water begins to boil at sea level is 212° Fahrenheit (or 100° Centigrade) and this temperature remains the same while the boil- ing continues. Increasing the heat simply increases the violence of the boiling. The steam given off is of the same temperature as the boiling liquid. Most pure liquids have a definite boiling point ; ether boils at 100° F, alcohol at 173° F, turpentine at 315° F. When the pressure of the atmosphere on the surface of the liquid is less than at the sea level, as on a moun- tain, where there is not so much air above pressing down on the surface of the liquid, the temperature of Effect of Heating Water Boiling Point 12 CHEMISTRY OF THE HOUSEHOLD. boiling is less. For example, the boiling point of water in Denver, Colorado, is about 202° F, and on the top of some of the mountains in the Himalayas, 180° F. People living in high mountain regions have difficulty in cooking with water or steam. Increasing the pressure on the surface of the liquid, on the other hand, raises the boiling point. This is seen when water boils in a confined space, as in a steam boiler. Under five pounds pressure of steam, water boils at about 22y° F and at 100 pounds pressure, at 337° F. An increase in the boiling point of water is caused by dissolved substances. A very strong solution of common salt boils at about 226° F, and a solution of sugar — syrup or molasses — boils at an increasing tem- perature as the water is lost. The temperature at which a syrup boils, is a meas- ure of its thickness or density. In many modern cook- ery books temperature tests are given for boiling sugar in making confections, which vary from 215° for a thin syrup, up to 350'' for caramel. In making maple sugar a "sugar thermometer" is often placed in the boiling syrup. At a given temperature, which is high- er for sugar cakes than for soft sugar, the proper con- centration is reached. latent Considerable heat is absorbed by the process of boil- ing. It requires 966 times as much heat to change a pound of water at the boiling point into steam as it does to raise it one degree Fahrenheit. The heat Heat WATER. 13 which is used to change the state of the water without changing its temperature is called latent heat from the Latin word, meaning hidden. The "hidden heat" is given out again when the steam is condensed. This same quantity of heat is absorbed when the water evaporates slowly ; hence the great cooling effect of large bodies of water. When water is cooled it shrinks slightly until the temperature of 39° F is reached. On further cool- ing it to the freezing point, 32° F (or 0° Centigrade) it increases in volume, so that ice takes up more space than the same weight of water and consequently floats. If this were not so, lakes and streams would freeze solid in winter and it is doubtful if they would melt completely during the summer in the northern part of the United States. To melt ice, 144 times as much heat is required to change the ice at 32° F into water at 32° F, as to raise the temperature of the same quantity of water one degree Fahrenheit. This is the latent heat of melting and the same amount of heat is given out when water freezes. Water thus serves as the great temperature regulator for the earth, for by evaporating, much of the heat of summer is absorbed, and before freezing, a great deal of heat must be given out and absorbed. Water has a much greater capacity of absorbing heat than any other common substance. For example, one pound of water will absorb ten times as much heat in being raised one degree as a pound of iron. The great- Freezing Heat Absorption 14 CHEMISTRY OF THE HOUSEHOLD. er absorbing capacity of water for heat explains why a kettle of fat heats up so much faster than the same weight of water under like conditions ; for the fat re- quires only one-third as much heat to raise it, say, to 200° F, as does the water. THE ATMOSPHERE When we leave the sleeping room, we open the win- dows to admit air. We may with advantage treat our lungs to an air bath by standing at the open win- dow or by going out of doors for a few minutes to take in five or ten deep breaths. Next, perhaps, we shall use drafts of air to help us make a fire in the range or in a fire place. Air as a Air is a real substance. It can be weighed. The air in a room 15 feet by 20 feet by 10 feet high weighs 210 pounds, and would fill ten ordinary water pails if liquified. Air will expand and may be compressed like other gases and it has been liquefied by intense cold and pressure. It requires considerable force to move it. When a bottle is full of air, no more can be poured in. Our houses are full of air all the time. It pervades all things — the cells and tissues of our bodies are full of air. Wood and some metals even contain a little. In breathing we take a little from the room, but it is im- mediately replaced by expired air, which is impure. Were there no exits for this air, no pure air could enter the house, and we should die of slow suffocation. The Substance THE ATMOSPHERE. 15 better built the house the quicker the suffocation. Fortu- nately no house is air tight. Air does pass out through the walls and cracks, and comes in around doors and windows, but unless there is a great difference in the temperature indoors and out, this fresh air is neither sufficient to replace the bad air nor to dilute it beyond harm. Therefore in ordinary weather, the air of all rooms must be often and completely changed either by special systems of ventilation or by intelligent action in the opening of doors and windows. The atmosphere surrounds the earth to a depth of pressure fifty miles or more. The effect of gravity of the earth on this mass is to produce a pressure or weight of air on all things. This pressure is about fifteen pounds on each square inch, but we do not notice it, for the pres- sure is the same on all sides of us and the internal pressure in the cells of our bodies balances the external pressure of the atmosphere. If it were not for the pressure of the air, we could not drink lemonade through a straw or pump a pail of water. When we exhaust part of the air by suction, we remove part of the pressure over the liquid in the straw and the air pressure on the surface in the glass forces the liquid up the straw. The same principle applies in a pump — the air is partially taken off the top of the water in the pipe, and then the pressure outside forces the water up in the pipe and by a proper valve arrangement, it is made to run into the pail. See Fig. 9, i6 CHEMISTRY OF THE HOUSEHOLD. Composition of Air Kitrogen The pressure of the atmosphere at the sea level is sufficient to force water up into a vacuum about 34 feet vertically ; but owing to mechanical imperfections of pumps, the practical limit is 27 or 28 feet rise be- tween the surface of the water and the valve of the pump. It is customary to use a force pump if water is to be raised to a height above this. Fig. 10. Unlike water, air is not the result of a chemical union of two unlike simple gases. Nevertheless, air contains more than one substance. It is made up chiefly of two gases simply mixed together, and each exhibits its own characteristics to some extent. Pure air consists of oxygen, which we have found constitutes one-third of water, and of nitrogen (and argon). The oxygen forms about a fifth and the nitrogen four-fifths of the air. Besides these, several other gases are found in small but varying quantities. To the oxygen gas is due the power of air to support combustion (fire) and life. Oxygen unites chemically with most other substances, and were the air all oxy- gen, the combustible part of the earth would soon be consumed by its own fires. Fortunately four-fifths of the air is a gas that has little power of combination and this nitrogen serves to dilute the oxygen and to weaken its force, much as water would dilute and weaken a strong and powerful chemical. The most marked characteristic of nitrogen is its sluggishness or inertness. Nitrogen, like oxygen, is a tasteless, odorless, colorless gas. It is fourteen THE ATMOSPHERE. 17 times as heavy as hydrogen. Though nitrogen from the air unites with other elements with difficulty, it is found in all living tissues, both animal and vegetable, and when these decompose the familiar substance, am- monia, is formed. This is a compound of hydrogen and nitrogen. Fig. 9. Suction Pump. Fig. 10. Force Pump. Carbon dioxide is always present in the atmosphere. This is one of the countless combinations of carbon, the element present in all animal and vegetable mate- rials. Carbon is nearly pure in the form of charcoal. Soot, graphite or the black lead of lead pencils, and the Carbon l8 CHEMISTRY OF THE HOUSEHOLD. diamond are other forms. Carbon unites very readily with oxygen and the gas formed by their chemical Carbon u^ion is Called carbon dioxide because it contains two Dioxide parts of oxygcu to one of carbon. Wood, coal, gas — almost everything that will burn in the air — and even our own bodies contain carbon, though we would not suspect its presence because it is combined with other substances and has merged its own character in those of the substances of which it forms a part. All our food contains carbon in its combinations. When we breathe we take into our bodies the oxy- gen of the air. This oxygen is needed by the various organs and is carried in the blood from the lungs to all parts of the body. During the circulation the oxygen is taken up by the cells and replaced by carbon dioxide. This is brought back by the blood to the lungs and breathed out. If we remain long in a closed room, a portion of the oxygen of the air in the room and of the substance of our bodies is changed into carbon dioxide, which is unfit to breathe. This is the reason for the special need of ventilation in the sleeping room. Water Water in the form of vapor is constantly passing ofif into the air from the surface of bodies of water, from vegetation, and from animal organisms, as in- visible vapor. The amount of water vapor present in the air is very variable. Warm air will hold more vapor than cold air. Ordinarily on a pleasant day, the atmosphere holds between 60 per cent and 70 per cent of the possible amount of water vapor, The atmosphere. 19 When the air is saturated or at the dew point, a sHght lowering of the temperature causes the vapor to condense. That air will absorb only a certain amount of moisture explains why a draft of air is necessary when drying clothes within doors and why the wash- ing drys slowly on a damp day. The presence of vapor in the air is shown by bring- ing a pitcher of ice water into a warm room. The air against the cold surface of the pitcher is cooled until the dew point is reached, when it deposits part of its moisture. Any person who wears glasses knows the effect of such condensation in going into a warm room from out of doors on a cold day. That the air exhaled contains water may be shown by breathing upon any bright, cold surface. The discomfort we feel in a crowded room is largely due to the excess of moisture resulting from the breathing and perspiration of so many persons. The danger of going from a crowded reception or **tea" into the open air is also due to it. Crowded rooms become very warm, the air soon becomes saturated with vapor and cannot take away the perspiration from our bodies. Our clothes thus become moist and the skin tender. When we go into the colder, drier air, clothes and skin suddenly give up their load of mois- ture. Evaporation absorbs heat ; the heat is taken from our bodies and a chill results. There is much to learn concerning the ventilation of rooms for social purposes. Dew Point How a Chill is Produced 20 CHEMISTRY OF THE HOUSEHOLD. ^ ^jj The air also contains a very small amount of a gas called argon. This was discovered in 1894. It resem- bles nitrogen so closely that it long escaped detection. Several other gases are present in minute quantities. COMBUSTION . Very likely a fire must be built in the cook stove. In order that chemical combination may take place, the conditions must be right. The stove is so con- structed that a current of air can pass from under the grate through the fire box, and funnel, to the chimney, and we must arrange that this air current shall not be unduly obstructed, for fuel will not burn without oxygen. Kindling Substauccs differ greatly as to the ease or difficulty with which they may be made to burn, or in chemical terms, with which they may be made to unite with oxygen. The temperature to which a substance must be heated before it will take fire is called the kindling point. We therefore place light materials, like shav- ings, pitch-pine chips, or paper on the grate, twisting the paper and arranging all in such a way that oxygen has free access to a large surface ; upon this we place small sticks of wood, piling them across each oJ:her for the same reason, and on this, in turn, hard wood or coal. The large stick of wood or the coal cannot be kindled with a match, but the paper or shavings can, and these in burning will heat the wood until it takes fire which then will kindle the coal. Point COMBUSTION. 21 To kindle the fire, we unthinkingly light a match. The burning of the match repeats the same principle we have described. The match is made by dipping the ends of small sticks of wood into melted sulphur, a substance more easily kindled than wood. When the sulphur is dried, the match is tipped with a preparation of phosphorus. Phosphorus has such a low kindling temperature that friction of the match against any rough surface heats it sufficiently to set it on fire. In burning, this sets fire to the sulphur and this, in turn, kindles the wood. Paraffine now has replaced sulphur. The products (substances formed) of the burning match are oxide of phosphorus, oxide of sulphur, and carbon dioxide and water from the carbon and hydro- gen of the wood. As our coal fire burns, we have two different oxides of carbon formed — carbon monoxide composed ' of one part carbon and one part oxygen, and carbon dioxide having two parts oxygen to one of carbon. The carbon monoxide formed in the lower part of the fire rises through the burning coals, takes up more oxygen at the top of the fire and forms carbon dioxide. The blue flames seen over a hard coal fire are caused by carbon monoxide burning. Carbon dioxide does not burn, since in this form the carbon holds as much oxygen as possible. The drafts and dampers so regulate the supply of oxygen that the fire may burn rapidly or slowly and that the harmful products of combustion may be carried out of the house by way of the chnnney. Chemistry of a Match Products of Combustion Carbon Monoxide 2.2 CHEMISTRY OF THE HOUSEHOLD. Constant Composition of tiie Air Elements It might be thought that with the miUions of human beings and animals and countless fires constantly using oxygen and giving off carbon dioxide, that the atmos- phere would soon consist of a large proportion of car- bon dioxide. Nature has wonderfully provided for this. Carbon dioxide, which is the waste matter of animals, is one of the foods of plants. Thus the trees of the forest and the shrubs and plants of the garden are continually taking in the carbon dioxide and giv- ing out pure oxygen, so that the carbon dioxide is kept at about three or four parts in 10,000 of air. As has been said, wood consists mainly of the sub- stances, carbon, oxygen, hydrogen, and nitrogen, to- gether with other substances in small amounts. The growing tree has taken these simple substances from the air and earth and stored them up in a complex form as w®od. The chemist calls the simple substances out of which different things are made, elements. Carbon, oxygen, nitrogen, sulphur, phosphorus, silver, gold, copper, iron, lead, tin, mercury, zinc, aluminum are the chemi- cal elements familiar to most people. When the \Vood is burned, or oxidized, its elements are made into new combinations, but in the burning no substance is de- stroyed. Some of the new products are invisible, it is true, but that they exist may be proved in many ways. One of the fundamental laws of chemistry is the Law of Conservation of Matter (substance). This may be stated as follows : The weight of all the COMBUSTION. 23 products made in a chemical action is exactly equal to the weight of all the substances used. That is, the weight of the dry wood plus the weight of the oxygen required to burn it, equals the combined weight of car- bon dioxide, water, and ashes produced. Matter can neither be destroyed nor created — it can only be changed or transformed. Scientists have reason to be- lieve that there is just the same amount of oxygen, nit- rogen, sulphur, iron and of all the other elements in the universe at the present moment as there was at the beginning of things. A familiar form of nearly pure carbon is charcoal. It is made by heating wood for a time with a very small amount of air. The vola- tile parts of the wood are driven off, leaving the carbon. The old fashioned method of making charcoal is shown in Fig. 1 1, where the burning of part of the wood gave the heat necessary for the making of the charcoal. At ^^^- ^^• the present time, most charcoal is made by the de- structive distillation of hard wood in iron stills ; the products being charcoal, crude wood alcohol, crude acetic acid, together with gas and wood tar, which last are burned to give the heat for the process. Charcoal is a porous substance and has the power of absorbing into its pores gases and even particles of OoBServation of Matter. Charcoal Kiln. Charcoal 24 CHEMISTRY OF THE HOUSEHOLD. coloring matter. A few pieces of charcoal added to the water in which flowers are standing, or plants growing, help to keep the water sweet by absorbing the impurities. Boneblack, a very finely powdered animal charcoal, is used to decolorize liquids. If it is mixed with a dark syrup, for instance, and the mixture vio- lently shaken, the color will be absorbed and filtration will give a nearly colorless syrup. Coal Coal is formed in almost every country on the earth, but the United States has the largest amount. It was originally wood and other carbonaceous mate- rial, once a part of living organism at a date of perhaps millions of years ago. During these years, the earth's crust has been subjected to slow upheavals and depres- sions, so that in some places, what was originally at the surface has been covered with thousands of feet of earthy matter, or possibly by the ocean. Under enor- mous pressure, the plants have been subjected to heat from the earth's interior. This is destructive distil- lation on the largest scale. Graphite In the making of coal if this distillation is com- plete, a substance called graphite is obtained. Graphite is the black lead used in lead pencils and in stove polish. It is a shiny, black mineral with a slippery feeling and is nearly lOO per cent carbon. If the distillation is less complete, hard coal, called anthracite containing about 90 per cent carbon, results. If still less per- fect, soft or bituminous coal, having varying per- centages of carbon, is formed. COMBUSTION. 25 Where the process goes on under water, peat is p^^^ found. This is partially formed coal, but little dis- tilled and contains only about 40 per cent carbon. Besides carbon, these substances are made up of gases composed of carbon and hydrogen, called hydro- carbons. These gases give the yellowish and orange flames in a coal fire. Pure carbon does not burn with flame — it merely glows. Anthracite coal contains only from 3 to 4 per cent of volatile matter, but bi- tuminous coal may have 30 to 40 per cent of these hydro-carbon gases. Coke is made by the destructive distillation of soft coke coal. Like charcoal, it is chiefly carbon, but contains more mineral matter (ash). The coke obtained as a bi-product in the manufacture of coal gas is rather soft, but when coke is made as the principal product, it is hard and brittle. Coke makes a very hot lire without flame, but does not last as well as hard coal. The ash should be allowed to accumulate in the grate when burning it. Many consider it an improvement over soft coal for household use and it might be used to advantage more than it is. Graphite is so hard and compact that it cannot be burned. Anthracite ignites with some difficulty and then burns slowly with intense heat. Bituminous coal ignites readily and burns well when coking there is sufficient draft. The "coking" variety cakes over on top and the fire must be broken up to allow the air to penetrate the fire. Soft coal should be put on the fire in small amounts as otherwise the hydro- 26 CHEMISTRY OF THE HOUSEHOLD. carbon gases escape iinburned and thus much heat vakie is lost. Smoke is made up of finely divided particles of carbon and is always an indication of in- complete combustion and, therefore, loss. ,>'^y\ r\i^ Fig. 12. Burner of a Blue Flame Oil Stove. Oil from tank (not shown) is forced np O, is vaporized in passing throvagh the straight tube, mixes with air at A, and burns with a blue flame at the top. Kerosene Kcroscnc and gasoline are also important fuels. Gas will be taken up under the subject of light. Petroleum is an oily liquid found in many places in large quanti- ties, particularly in Pennsylvania and Ohio. It is made up almost entirely of compounds of carbon and hydrogen ( hydro-carbons ) . When the crude petroleum from the Pennsylvania district is purified by distillation and other processes, the main product is kerosene. The lighter and more volatile products are gasoline, naphtha, and benzine — all three having much the same composition. Gaso- line is the most volatile. Among the heavier products are various lubricating oils, vaseline, and paraffin. In order to burn, kerosene must be vaporized. In the new blue flame oil stoves, various devices are em- COMBUSTION. 27 ployed to vaporize the oil. In F'ig. 12 the oil passes through a tube heated by the flame, where it is changed to vapor which is mixed automatically with air and is then burned. Sometimes an alcohol flame is used to start this process, but the flame of the burning oil itself continues it. A slight pressure of air is main- tained in the oil reservoir to give a constant small jet of oil to be vaporized. In other styles of stoves, the oil is fed automatically by gravity to a hollow ring, when it becomes heated to the point that it gives vapor. The vapor mixes with air and burns with a blue flame. Fig. 13. Blue Flame Oil Stoves Fig. 13. Blue Flame Oil Stove, Showing Oil Reservoir and Light- ing Ring. Gasoline is burned on much the same principle as GaioUne kerosene. It vaporizes much more easily and the pres- sure for the flow of the gasoline is furnished usually by having the tank a few feet above the burner. 28 CHEMISTRY OF THE HOUSEHOLD. rj*»h '^^^ measure of safety of kerosene is the temperature ^oi"t 2X which it will give off an inflammable gas. This is called the iia^h point and is determined by heating the oil slowly and observing the temperature at which a flash can be produced by applying a lighted taper to the surface of the oil. Below the flash point, there is no danger of explosion from oil. Most states in the United States have a legal flash point, or a fire test, below which standard kerosene cannot be sold. The flash point of good kerosene is 120'' F. The fire test is the temperature at which the oil will take fire and hum when a light is applied. This is about 30° F higher than the flash point. The ordinary tempera- ture of the room is above the flash point of gasoline, naphtha, benzine, etc. In other words, these sub- stances are constantly giving out an inflammable vapor. Fuel A comparison of the heating value of the various fuels will be of interest. Practical tests of the amount of steam produce.d in a steam boiler have shown that one cord of ordinary wood is approximately equal to one-half ton of coal ; a gallon of oil (or gasoline) is equal to about twelve pounds of coal; 1,000 cubic feet of coal gas is equal to 50 or 60 pounds of coal, or about four and one-half gallons of oil. Hard coal has a little higher fuel value than soft coal, because the com- bustion is commonly more perfect. Coke is nearly equal to hard coal by weight, but is much more bulky. It is usually sold by measure. A bushel of coke weighs 40 pounds, of anthracite 67 pounds, and of soft Value FOOD. 29 coal y6 pounds. Damp wood is a much poorer fuel than dry wood, because so much heat is absorbed and wasted in changing the water into steam. The heat given oi¥ by a fuel is not the only point to be considered. In the cook stove, but a small portion of the heat given off by the solid fuel can be used for cooking, as most of it is radiated into the room or carried up the chimney. In the gas or oil stove, the flame may be applied exactly where it is wanted, so that the proportion of heat which can be used is much greater. Moreover, the flame can be shut off instantly when wanted no longer and all expense stopped. On the other hand, the range usually serves to heat the water of the hot water system, incinerate garbage, and in winter helps to heat the house. FOOD Having the fire well under way the housekeeper turns her attention to the breakfast. A great variety of chemical actions may here be considered. In the first place, why must we "eat to live ?" Wherever there is life, there is chemical change; and as a rule a certain degree of heat is necessary ^y ^» in order that chemical change may occur. Vegetation does not begin in the colder climates until the air be- comes warmed by the heat of the spring. When the cold of winter comes upon the land vegetation ceases. Since many animals live in temperatures in which plants would die, it is evident that they must have some 30 CHEMISTRY OF THE HOUSEHOLD. Com'buBtion in the Body Vital Temperature Air as Food source of heat in themselves. This is found in the union of the oxygen of the air breathed with car- bonaceous matter eaten as food and the formation of carbon dioxide and water, just as in the combustion of wood or coal. Only instead of this union taking place in one spot and so rapidly as to be accompanied by light, as in the case of fire, it takes place slowly and continuously in each living cell. Nevertheless, the chemical reaction seems to be identical. The heat of the human body must be maintained at 98.5° F — the vital temperature — the temperature neces- sary for the best performance of the normal functions. Any continued variation from this degree of heat in- dicates disease. Especially important is it that there be no considerable lozvering of this temperature, for a fall of one degree is dangerous, since in that case the chemical changes necessary to the body cannot be car- ried out. The slow combustion or oxidation of the carbon and hydrogen of food cannot take place without an abundance of oxygen ; hence the diet of the animal must include fresh air — a point not always considered. The amount of oxygen taken in by the body daily is equal to the sum of all the other food elements. Except water, two-thirds of these foods consists of some form of starch or sugar — the socalled carbohy- drates, in which the hydrogen and oxygen are found in the same proportion as in water. The power to do mechanical work comes from the FOOD. 31 combustion of fuel. The body is a living machine capable of doing work, raising weights, pulling loads, and the like. The animal body also requires fuel in order to do such work as thinking, talking, even wor- rying. For the present, then, we will say that food is necessary, (i) to preserve the vital temperature and (2) to enable the body-machine to do its work. Suppose we begin our breakfast with fruit, say, an orange or a banana. Fruits are especially rich in sugars and these are composed of carbon, hydrogen, and oxygen. If sugar is placed upon a stove, it will melt and steam (water) will pass off into the air, leaving the black charcoal (carbon) on the stove. Moreover, sugars burn easily and fiercely. We shall get both heat and energy from our fruit. Within the body it will be changed into water and carbon dioxide- Fruits contain a large percentage of water; but the banana is capable of giving more energy and heat 'than the orange, because it has much less water and more sugar. Fruit loses in drying a large portion of its water, so that dried fruits contain a larger percentage of food materials than fresh fruits. For instance, raisins are 60 per cent grape sugar. Fruits consist of a loose net-work of a woody ma- terial holding the soft pulp and this woody fibre, called cellulose, is practically indigestible. Cooking softens this, making cooked fruits easier to digest. Fruit Cellulose 32 CHEMISTRY OF THE HOUSEHOLD. SUGARS AND STARCHES. At breakfast some sugar from the sugar bowl may be added to the fruit. Many people add sugar tc the oatmeal or other cereal eaten, although it is often held by teachers of dietetics that this is not a good place to use it, for proper cooking and thorough mastication of the cereal will bring out a rich sweetness due to changes explained later. Country boys know how sweet a morsel is made by chewing raw grains, especially wheat. Possibly a glass of milk is taken at breakfast and this contains another kind of sugar — milk sugar — in about 5 per cent. Coffee and tea are usually sweet- ened, so that a considerable part of the breakfast may be of this class of foods — a quickly burning material giving heat and energy. Cane There are several different sugars recognized by chemists ; these are cane sugar or sucrose, grape sugar or glucose, milk sugar or lactose, and fruit sugar or levulose. Cane sugar is obtained from the juices of many plants, notably sugar beets, sugar cane, the palm, and as maple sugar from the rock-maple trees. Molasses and brown sugar are obtained during the manufacture of white sugar from sugar cane. Cane sugar is composed of carbon, hydrogen, and oxygen in the proportion of twelve parts of carbon to eleven parts of water. When sugar is heated it is chemically changed, more or less, according to the degree of heat and the rapidity with which it parts with its water. Sugar SUGARS AND STARCHES. 33 Heating it gradually, we obtain first straw colored barley sugar, then brown caramel, and finally black carbon. Grape sugar is found in honey and in all ripe fruits. Grape It consists of carbon, hydrogen, and oxygen in some- "^" what different proportions from what they occur in cane sugar. It appears on the outside of dried fruits, such as raisins. It is only two-fifths as sweet as cane sugar. Large quantities are manufactured from corn starch. Milk sugar is similar to cane sugar in composition. jjiu^ It is obtained from the whey of milk. It is hard ^"^" and gritty and not very sweet to taste. When milk sours, it is because this sugar is fermented and changed into lactic acid. The acid causes the milk to curdle. Fruit sugar or levulose occurs with glucose (grape j-j.^-^. sugar) in fruits. It is about as sweet as cane sugar ^"^" but it does not crystallize. A marked characteristic of all sugars is their solu- bility and all but the last are crystalline substances, that is, will form crystals. At breakfast bread, toast, or some cereal like oat- meal or wheat, usually follows the fruit course. These foods are prepared from grains (seeds) and contain much nutriment in a condensed form. They supply the body with starch and some nitrogenous food. But the body cannot use starch as such. It must be changed into a form of sugar called starch sugar, or maltose. While we are following Mr. Glad- starch 34 CHEMISTRY OF THE HOUSEHOLD. Source of Starch stone's rule and chewing each mouthful of our toast twenty-five times, we will consider what starch is like and how it is made available for use. Starch is found in greater or less abundance in all plants and is laid up in large quantities in the seeds of many species. See Fig. 14. Rice is nearly pure starch ; wheat and the other cereals contain sixty to seventy per cent of it. Some tubers, such as potatoes, contain it although in less quantity — ten to twenty per cent. It is formed by means of the living plant-cell and the sun's rays, from the carbon dioxide and water contained in the air and it is the end of the plant - life — the stored energy of the summer. It is prepared and stored by the parent for the food for the young plant until the latter can start its own starch factories. Starch in its common forms is insoluble in water. It dissolves partially in boiling water, forming a trans- parent jelly when cooled, as every housekeeper knows. The cellulose which occurs in various forms in the shells and skins of fruits, in their membraneous parti- tions, and in cell walls, is an allied substance. Fig. 14. Starch Much Magnified a, Potato Starch; b, Corn Starch. SUGARS AND STARCHES. 35 DIGESTION Digestion is primarily synonymous with solution. All solid food materials must become practically solu- ble before they can pass through the walls of the di- gestive system. Starch and like materials must be transformed into soluble substances before absorption can take place. Cane-sugar, though soluble, has to undergo chemical change before it can be absorbed. By these changes it is converted into grape and fruit sugars. These and milk sugar are taken directly or with little change into the circulation. To this fact is due a large part of the great nutritive value of the dried fruits, as raisins, dates, and figs, and the advan- tage of milk-sugar over cane-sugar for children or in- valids. Under certain conditions — weakened digestive power or excess of sugar — cane-sugar may remain so long in the stomach before the change takes place that fer- mentation sets in and a ''sour stomach" results. This is one of the dangers of too much candy. The chemical transformations of starch and sugar have been very carefully and scientifically studied with reference to brewing and wine-making. Several of the operations concerned necessitate great precision in respect to temperature and length of time, and these operations bear a close resemblance to the process of bread-making by means of yeast. There are two distinct means known to the chemist by which starch is changed to sugar. One is by the Digestion of Starch Starch Conversion Ferments Conversion in the Body 36 CHEMISTRY OF THE HOUSEHOLD use of acid and heat, which changes the starch into sugar, but can go no farther. The other is by the use of a class of substances called ferments, some of which have the power of changing starch into sugar, and others of changing the sugar into alcohol and carbon dioxide. These ferments are very important in all vegetable and animal life. Some are formed by small plants like yeast, which is often present in the air. Fig. 15. Among the well known ferments is one formed in sprouting grain, which is called diastase or starch con- verter, and under the influence of warmth, changes the starch into a sugar. The starch first takes up water ; then under the in- fluence of the ferment, is changed into maltose, a form of sugar which is easily soluble in water. A similar process is carried on in the preparation of the malted foods on the market. The sanie cycle of chemical changes goes on in the human body when starchy substances are taken as food. Such food is moistened with saliva and warmed in the mouth, becoming well mixed through mastica- tion. It thereby becomes impregnated with ptyalin, a ferment in the saliva, which can change starch into sugar, as can the diastase of the malt. The mass then passes into the stomach and the change, once begun, goes on. In the intestines the sugar formed is absorbed into the circulatory system and by the life proc- Fig. 15. Yeast Highly Magnified. COOKING. 37 esses, is oxidized, that is, united with more oxygen and changed finally into carbon dioxide and water, from which it was made by the help of plant life and sun light. No starch is utilized in the human system as starch. It must undergo transformation before it can be ab- sorbed. Therefore, starchy foods must not be given to children before the secretion of the starch converting ferments has begun, nor to any one in any disease where the normal action of the glands secreting these ferments is interrupted. Whatever starch passes out of the stomach unchanged, meets with a very active converter in the intestinal juice. If grains of starch escape these two agents, they leave the system in the same form as that in which they entered it. Digestion of Starch Early man, probablv, lived much like the beasts, taking his food in a raw state. Civilized man requires much of the raw material to be changed by the action of heat into substances more palatable and already partly digested. The chemistry of cooking the raw materials is very simple. It is in the mixing of incongruous materials in one dish or one meal that complications arise. The cooking of starch, as rice, farina, etc., requires little explanation. The starch grains are prepared by the plant to keep during a season of cold or drought and are very close and compact ; they need to be Cooking of Starch 38 CHEMISTRY OF THE HOUSEHOLD. swollen and distended by moisture in order that the chemical change may take place readily. Starch grains may increase to twenty-five times their bulk by absorb- ing water. The cooking of the potato and other starch-contain- ing vegetables, although largely a physical or mechani- cal process is very necessary as a preparation for the chemical actions of digestion ; for raw starch has been shown to require a far longer time and more digestive power than cooked starch. Change takes place slowly, even with thorough mastication, unless the starch is swollen and heated, and, in case the intestinal secre- tion is disturbed, the starch may not become converted at all. Bread Oi^^i* brcakfast will undoubtedly contain bread. Bread of some kind has been used by mankind from the first dawn of civilization. During the earlier stages it consisted chiefly of powdered meal and water baked in the sun or on hot stones. This kind of bread had the same characteristics as the modern sea-biscuit, crackers, and hoe cakes, as far as digestibility was concerned. It had great density ; it was difficult to masticate ; and the starch in it presented but little more surface to the digestive fluids than that in the hard compact grain, the seed of the plant. Experience must have taught the semi-civilized man that a light porous loaf was more digestible than a dense one. Probably some dough was accidentally left exposed ; yeast plants settled upon it from the air ; Bread or Yeast COOKING. 39 fermentation set in, and the possibility of porous bread was thus suggested. A light, spongy, crisp bread with a sweet, pleasant weai taste, is not only aesthetically but chemically con- sidered the best form in which starch can be presented to the digestive organs. The porous condition is de- sired in order that as large a surface as possible may be presented to the action of the chemical converter, the ptyalin of the saliva, and later to other digestive ferments. There is also better aeration during the process of mastication. Very early in the history of the human race, leavened Leaven bread seems to have been used. This was made by allowing flour and water to stand in a warm place until fermentation had well set in. A portion of this dough was used to start the process anew in fresh portions of flour and water. This kind of bread had to be made with great care, for germs different from yeast might get in, forming lactic acid — the acid of sour milk — and other substances unpleasant to the taste and harm- ful to the digestion. A sponge made from perfectly pure yeast and kept pure may stand for a long time after it is ready for the oven and still show no signs of sourness. On account of the disagreeable taste of leaven and because of the possibility that the dough might reach the stage of putrid fermentation, chemists and physi- cians sought for some other means of rendering the bread light and porous. The search began almost as 40 CHEMISTRY OF THE HOUSEHOLD. soon as chemistry was worthy the name of a science, and one of the early patents bears the date 1873. Much time and thought have been devoted to the perfecting of unfermented bread; but since the process of beer- making has been universally introduced, yeast has been readily obtained, and is an effectual means of giv- ing to the bread a porous character and a pleasant taste. Since the chemistry of the yeast fermentation has been better understood, a change of opinions has come about, and nearly all scientific and medical men now recommend fermented bread, if well baked. Chemistry of ^^^^ chcmical rcactious concerned in bread-making Bread-Making ^j.^ similar to thosc iu beer-making. To the flour and warmed water is added yeast, a microscopic plant, capable of causing the alcoholic fermentation. The yeast begins to act at once, but slowly; more rapidly if sugar has been added and the dough is a semi-fluid. \^'ithout the addition of sugar no change is evident to the eye for some hours, as the fermentation of starch to sugar by the diastase present gives no gaseous products. The sugar is decomposed by the yeast plant into alcohol and the gas, carbon dioxide ; the latter product makes itself known by the swelling of the whole mass and the bubbles which appear on the sur- face. It is the carbon dioxide, which causes the sponge- like condition of the loaf by reason of the peculiar tenacity of the gluten, one of the constituents of wheat. It is a well-known fact that no other kind of grain will COOKING. 41 make so light a bread as wheat. It is the right pro- portion of gluten (a nitrogenous substance to be con- sidered later) which enables the light loaf to be made of wheat flour. The production of carbon dioxide is the end of the chemical process. The rest is purely mechanical. The baking of the loaf has for its object to kill the ferment, to heat the starch sufficiently to render it easily soluble, to expand the carbon dioxide and drive off the alcohol, to stiffen the gluten, and to make chem- ical changes which shall give a pleasant flavor to the crust. The oven must be hot enough to raise the tem- perature of the inside of the loaf to 212° F, or the bacteria will not all be killed. A pound loaf, four inches by four inches by nine inches long, may be baked three-quarters of an hour in an oven where the temperature is 400" F, or for an hour and a half, when the temperature during the time does not rise above 350° F. Quick baking gives a white loaf, because the starch has undergone but little change. The long, slow baking gives a yellow tint, with the desirable nutty flavor, and crisp crust. Different flavors in bread are supposed to be caused by the different varieties of yeast used or by bacteria, which are pres- ent in all doughs, as ordinarily prepared. The brown coloration of the crust, which gives a peculiar flavor to the loaf, is caused by the formation of substances analogous to dextrine and caramel, due to the high heat to which the starch is subjected. Object of Saking The Crust 42 CHEMISTRY OF THE HOUSEHOLD. One hundred pounds of flour are said to make from 126 to 150 pounds of bread. This increase of weight is due to the incorporation of water, possibly by a chemical union, as the water does not dry out of a loaf, as it does out of a sponge. The bread seems moist when first taken from the oven, and dry after standing some hours, but the weight will be found to be nearly the same. It is this probable chemical change which makes the difference, to delicate stomachs, between fresh bread and stale. A thick loaf is best when eaten after it is twenty-four hours old, although it is said to be ''done" when ten hours have passed. Thin biscuit do not show the same ill effects when eaten hot. The bread must be well baked in any case, in order that the process of fermentation may be stopped. If this be stopped and the mastication be thorough, so that the bread when swallowed is in finely divided por- tions instead of in a mass or ball, the digestibility of fresh and stale bread is about the same. Water The cxpausiou of water or ice into more than seven- teen hundred times its volume of steam is sometimes taken advantage of in making snow-bread, water-gems, etc. It plays a part in the lightening of pastry and crackers. Air, at 70 degrees, doubles its volume at a tempera- ture of 560 degrees F, so that if air is entangled in a mass of dough, it gives a certain lightness when the whole is baked. This is the cause of the sponginess of cakes made with eggs. The viscous albumen or COOKING. 43 ''white of egg'' catches the air and holds it, even when it is expanded, unless the oven is too hot, when the sudden expansion is liable to burst the bubbles and the cake falls. FATS If cream instead of milk is used on the cereal or in the coffee, this with the butter on the bread, will add a considerable amount of another important food, fat. Fats form a large class of food stuffs which in- clude the animal fats like cream, butter, suet, lard, cod liver oil and tallow, and vegetable fats like olive and cotton-seed oils, etc. Within the animal body all fats are liquids, being held in little cells which make up the fatty tissue. The digestion of fats is probably something like a process of soap making. With the intestinal fluids, the bile especially, the fats form an emulsion in which the globules are finely divided, and in some way are rendered capable of passing through the membranes into the circulatory system. The change, if any, does not destroy the properties of the fatty matters. If we define cooking as the application of heat, then whatever we do to fats in the line of cooking is liable to hinder rather than help digestibility. Fats may be heated to a temperature far above that of boiling water without showing any change ; but there comes a point, different for each fat, where re- actions take place, the products of which irritate the mucous membranes and therefore interfere with diges- Digestion of Fats Cooking' of Fats 44 CHEMISTRY OF THE HOUSEHOLD. tion. It is the volatile products of such decomposition which cause the familiar action upon the eyes and throat during the process of frying, and also, the tell- tale odors throughout the house. The indigestibility of fatty foods, or foods cooked in fat, is due to these harmful substances produced by too high temperature. Composition Many fats are solid at ordinary temperatures, while others are always liquids, but all fatty materials have a similar composition. When pure they contain only carbon, hydrogen, and oxygen. They differ from starch and sugar in the proportion of oxygen to the carbon and hydrogen, there being very little oxygen relatively in fats, hence more must be taken from the air for their combustion. If persons eat much fat they must have more fresh air to burn it. A person confined to the house needs to be careful what fats, and how much, are taken. Heat from ^^c pouud of starch rcquircs one and two-tenths ^**^ pounds of oxygen, while one pound of suet requires about three pounds of oxygen for perfect combustion. This combustion of oxygen with the large amoimt of hydrogen, as well as with the carbon, results in a greater quantity of heat from fat, pound for pound, than can be obtained from starch or sugar. Experi- ments indicate that the fats yield more than twice as much heat as the carbohydrates ; hence people in Arctic regions use large amounts of fat and every- where the diet of winter may safely contain more fat than that of summer. NITROGENOUS FOODS. 45 Both fats and carbohydrates are the sources of the energy or work done by the body as well as the heat to keep up the vital temperature and they must be increased in proportion as the mechanical work of the body increases. A man breaking stone needs more fat or starch than the student. If a quantity is taken at any one time greater than the body needs for im- mediate work, the surplus will be deposited as fat, and this will be drawn in case of a lack in the future sup- ply of either ; it is like a bank account. Food a Source of Energy NITROGENOUS FOODS The animal body is more than a machine. It re- quires fuel to enable it not only to work but also to live, even without working. A part of the food eaten must go to maintain the body, for while the inani- mate machine is sent periodically to the repair-shop, the living machine must do its own repairing, day by day and minute by minute. The adult animal lives, repairs waste, and does work ; while the young animal does all these and more — it grows. For growth and repairs something else is needed beside starch and fat. The muscles are the instruments of motion, and they must be nourished in order that they may have power. The nourishment is carried to them by the blood in which, as well as in muscular tissue, there is found a food element which we have not heretofore considered, namely, nitrogen. It has been proved that the use of the muscles and the brain sets free certain Nitrogen Necessary 46 CHEMISTRY OF THE HOUSEHOLD. Proteids Gelatinoids nitrogenous compounds which pass out of the system as such, and this loss must be suppHed by the use of some kind of food which contains nitrogen. Starch and fat do not contain this element ; therefore thev cannot furnish it to the blood. The American breakfast will probably include meat, fish, or eggs. These are examples of the nitrogenous food-stuffs. Nitrogenous food compounds are some- times classed together under the name of proteins. These may be divided into proteids, gelatinoids, and extractives. The proteids all resemble albumin, which is found nearly pure in the white of an tgg. These in some form are never absent from animal and vegetable or- ganisms. They are most abundant in animal flesh and in the blood. Other common articles of diet belong- ing to this group in addition to albumin, are the curd of milk (casein), the lean of animal flesh and fish and gluten of wheat, and the legumin of peas and beans. The proteids are the most important nitro- genous food materials. They build up and repair the muscles, tendons, cartilage, bones, and skin and supply the albumin of the blood and other fluids of the body. The animal skeleton — horns, bones, cartilage, con- nective tissues, etc. — contains nitrogenous com- pounds which are converted by boiling into substances that form with water a jelly-like mass. These are known as the gelatinoids and are so named because of their resemblance to gelatin. Although somewhat NITROGENOUS FOODS. 47 similar to the proteids in composition they are not thought to be true flesh formers. However, they do help out the proteids in some unknown way. The chief constituent of the connective tissues of meats is collagen. This is insoluble in cold water, but in hot water becomes soluble and yields gelatin. Col- lagen swells when heated and when treated with dilute acids. Steak increases in bulk when placed over the coals, and tough meat is rendered tender by soaking in vinegar. Meat a few days old is tough, for the collagen is dry and hard. In time it becomes softened by acids which are secreted by bacteria either in or on the meat ; the meat thus becomes tender and easily masticated. Tannic acid has the opposite effect upon collagen, hardening and shrinking it. This ef- fect is taken advantage of in tanning, and is the dis- advantage of boiled tea as a beverage, since tea always contains a little of this tannic acid when freshly made and much more if the tea is boiled. The last class of nitrogenous compounds are the extractives, so called because they are readily extracted by water from meat where they principally occur. The proteins of this class are thought to have little value as food, but they give the flavor to meats, etc., and are therefore of great importance. They are stimulants, somewhat of the nature of caftein of coffee and the thein of teat Collagen Extractives 48 CHEMISTRY OF THE HOUSEHOLD. COOKING OF NITROGENOUS FOOD-STUFFS. Cooking should render nitrogenous food more solu- ble because here, as in every case, digestibility means solubility. Egg albumin is soluble in cold water, buv coagulates at about i6o° F. At this point it is ten- der, jelly-like, and easily digested, while at a higher temperature it becomes tough, hard and dissolves with difficulty. Therefore, when the white of ^gg (al- bumin), the curd of milk (casein), or the gluten of wheat are hardened by heat, a much longer time is required to effect solution. Albumin As prcviously stated, Qgg albumin is tender and jelly-like when heated from i6o° F to i8o° F. This fact should never be forgotten in the cooking of eggs. Raw eggs are easily digested and are rich in nutri- ment ; when heated just enough to coagulate the al- bumin or *'the white," their digestibility is not ma- terially lessened ; but when boiled, the albumin is rendered much less soluble. In frying eggs, the fat often reaches a temperature of 300° or over — far above that at which the albumin becomes tough, hard, and well-nigh insoluble. There is much albumin in the blood, therefore the juices of meat extracted in cold water form a weak albuminous solution. If this be heated to the right temperature the albumin is coagulated and forms the "scum" which many a cook skims oft* and throws away. In doing- this she wastes a portion of the nutriment. NITROGENOUS FOODS. 49 Experiments on the digestibility of gluten have Gluten proved that a high temperature largely decreases its solubility. Subjected to artificial digestion for the same length of time, nearly two and one-half times as much nitrogen was dissolved from the raw gluten as from that which had been baked. When gluten is combined with starch, as in the cereals, the difficulties of correct cooking are many, for the heat which increases the digestibility of the starch decreases that of the gluten. Experiment.- The gluten in wheat flour may be ob- tained as follows: Place half a cupful of flour in a muslin bag and knead under water. The starch will work out through the bag. After a time all the starch may be so separated. A brown, elastic, stringy mass remains in the muslin. This is gluten, the nitrogenous part of the flour. The same principle of cooking applies to casein of casein milk, although to a less extent. There seems to be no doubt that boiling decreases its solubility, and con- sequently, its digestibility for persons of delicate di- gestive power. The nitrogenous substances of meat consist of solu- Meat ble albumin, chiefly in the blood and juices, the al- buminoids of the fibres, the gelatinoids of the connect- ing tissues, and the extractives. The cooking should soften and loosen the connective tissue, so that the lit- tle bundle of fibre which contains the nutriment may fall apart easily when brought in contact with the so CHEMISTRY OF THE HOUSEHOLD. Broth and Soup Effect of Temperature on Meat teeth. Any process which toughens and hardens the meat should be avoided. When it is desired to retain the juices within the meat or fish, it should be placed in boiling water so that the albumin of the surface may be hardened and prevent the escape of the albumin of the interior. The temperature should then be lowered and kept between i6o and i8o degrees during the time needed for the complete breaking down of the connective tissues. When the nutriment is to be used in broths, stews, or soups, the meat should be placed in cold water, heat- ing very slowly and the temperature not allowed to rise above i8o° F until the extraction is complete. The extracted meat still retains the greater part of its original proteid substances. It is tasteless and un- inviting, but when combined with vegetables and flavoring materials may be made into a palatable and nutritious food. Experiment. To show the effect of water at dif- ferent temperatures upon raw meat, place a bit of lean meat about as large as the finger in a glass of cold water and let it stand an hour. The water becomes red, and the meat grows white. Pour off this water and boil it. A scum rises to the surface. The albu- min dissolved has been rendered insoluble by heat. Put a bit of raw meat into boiling water, and boil it hard several minutes. The meat is toughened by the process. The outside of the meat is hardened first, and very little of the nutriment dissolves in the water. of Froteids FOOD. SI Put the meat into cold water and bring the tem- perature slowly to the boiling point; then allow it to simmer gently for some time. The meat is tender, and some of the nutriment is in the water. This is the method employed in making a stew. A little fat which is always present even between the fibre of the lean meat will be melted out and rise to the top of the water. We have seen that the ferment in the saliva changed Digestion the starch into a sugar. The ferment in the gastric juice, pepsin, with the help of an acid (principally hydrochloric acid) changes the albuminoids into pep- tones in the stomach. This change is completed in the intestines. The peptones are soluble in water and are absorbed into the blood. SUMMARY OF THE EFFECTS OF COOKING The object of all cooking is to make the food-stui¥s more palatable or more digestible, or both combined. In general, the starchy foods are rendered more di- gestible by cooking; the albuminous and fatty foods less digestible. The appetite of civilized man craves and custom encourages the putting together of raw materials of such diverse chemical composition that the processes of cooking are also made complex. Bread — the staff of life — requires a high degree of heat to kill the plant-life, and long baking to prepare the starch for solution ; while, by the same process, the gluten is made less soluble. Fats, alone, are easily digested, but in the ordinary method of frying, they 52 CHEMISTRY OF THE HOUSEHOLD. not only may become decomposed themselves, and therefore injurious ; but they also prevent the necessary action of heat, or of the digestive ferments up^n the starchy materials with which the fats are mixed. The effects of cooking upon the solubility of the three important food-principles may be broadly stated thus : Effeci on Stavcky foods are made more soluble by long cook- soiubihty -j^g ^^ moderate temperatures or by heat high enough to change a portion of the starch to dextrine, as in the brown crust of bread. Nitrogenous foods. The animal and vegetable al- bumins are made less soluble by heat ; the gelatinoids more soluble. Fats are readily absorbed in their natural condition, but are decomposed at very high temperatures and their products become irritants. MINERAL MATTER The remaining ingredient of the food of our break- fast to be considered is the mineral matter which con- stitutes the ash when food-products are burned. There is only 5 or 6 per cent of mineral elements in our bod- ies, but these materials are necessary to life and health. They are found chiefly in the bones and teeth, but are present also in the flesh, blood, and other fluids. Phos- phate of calcium forms the principal mineral part of the bones. Common ^^^^ ^^^^^ ^^'^ ^'^^ coutains a small amount of mineral ^*^* matter which forms the ashes when food is burnecl, MINERAL MATTER. 53 This mineral matter gives the body the mineral salts which it needs ; but in addition to this, most people de- sire and eat a considerable quantity of common salt every day. The amount eaten is far in excess of the sodium and chlorine the body requires, though sodium is an important constituent of many of the fluids of the body, and chlorine is found in hydrochloric acid of the gastric juice, the digestive fluid of the stomach. A great diversity of opinion exists as to the desirability of much salt in the diet, but the balance of evidence in- dicates that a liberal amount of salt is not harmful, but rather beneficial. Experiment. To show the mmeral part of bones, place a moderate sized bone on a hot coal fire for half an hour or longer. To show the gelatinoids of bones, place a small bone in a shallow dish and cover with strong vinegar or weak hydrochloric acid (muriatic acid) and let stand over night or longer. The acid \\\\\ dissolve out the phosphate of calcium leaving the animal matter. Coffee, an important part of the breakfast to most Flavor people, introduces an important feature of the chem- istry of cooking — the production of the proper flavor. The chemical changes involved are too subtile for ex- planation here — indeed many are not understood. The change in the coffee berry by roasting is a familiar il- lustration. The heat of the fire causes the breaking up of a substance existing in the berry, and the forma- tion of several new ones. If the heat is not sufficient, Production 54 CHEMISTRY OF THE HOUSEHOLD, the right odor will not be given ; if it is too great, the aroma will be dissipated into the air, or the compound will be destroyed. Broiling steak is another illustration — a few seconds too long, a few degrees too hot, and the delicate morsel becomes an irritating mass. The chemistry of flavor- producing is the application of heat to the food material in such a way as to bring about the right changes and only these. Flavors in addition to the pleasure they give to eating have the advantage of stimulating the flow of digestive fluids and making digestion more easy. DECAY The clearing away of the breakfast introduces to the housekeeper two important problems: — (i) the pres- ervation of the remaining food from decay; (2) the proper cleaning of the articles used during the meal and its preparation. Decay is caused by minute vegetable organisms known as moulds and bacteria. Both are present in the air either as the plants themselves or as their spores, the reproductive cells, ready to grow whenever they fall upon suitable soil. When these grow upon animal or vegetable substances, a variety of new com- pounds are formed, many of them taking oxygen from the air, so that finally the carbon becomes carbon diox- ide, the hydrogen is oxydized to form water, and the other elements in their turn also become oxides, so that the decaying substance is utterly destroyed and Decay Not DECAY, 55 new substances made in its place. When organic sub- stances are protected from the action of these living plants, decay will not ensue. The old idea was that oxygen caused decay, but many experiments disprove this. Oxveen alone does caused by . ' , Oxygen Alone not produce this result, but oxygen with ''germs" will do so. These "germs" develop much more slowly in the cold, so that food is placed in the refrigerator or in a cool place and away from the dust. The problems introduced by these living plants, their life history and their work, as well as the methods of prevention and care against their ravages, belong rather to household bacteriology than to chemistry. We are ready therefore to pass on to our next prob- lem, that of cleaning. TEST QUESTIONS The following questions constitute the ''written reci- tation" which the regular members of the A. S. H. E. answer in writing and send in for the correction and comment of the instructor. They are intended to emphasize and fix in the memory the most important points in the lesson. CHEMISTRY OF THE HOUSEHOLD. PART I, Read Carefully. Place your name and address on the first sheet of the test. Use a light grade of paper and write on one side of the sheet only. Do not copy answers from the lesson paper. Use your own words, so that your instructor may know that you understand the subject. Read the lesson paper a num- ber of times before attempting to answer the questions. 1. What do you understand a "chemical element" to be? Name all that you have ever seen. 2. What is a "saturated solution?" Name the substances usually found in the house which are soluble in water. 3. What causes atmospheric pressure? Explain some effects of it. 4. Why must the diet of animals include fresh air ? 5. Explain the efifect of cooking on starch, (b) On fats, (c) On proteids. 6. What are the products of combustion in burning coal or wood ? 7. What is meant by "conservation of matter?" 8. How can the boiling point of water be raised? How may it be lowered? CHEMISTRY OF THE HOUSEHOLD. 9. V/hat is meant when It is said that a chemical substance always has the same composition ? 10. What is "latent heat?" 11. What can you say of the composition of meat? 12. Explain the physical and chemical changes which starch must undergo before it is absorbed into the circulation. 13. What can you say of the chemistry of bread- making ? 14. Why is distilled water pure? 15. Explain the composition of water. 16. Describe the chemistry of a sulphur match. 17. How is charcoal prepared ? How is coke made ? 18. Why does the proportion of carbon dioxide in the atmosphere not increase? 19. In what different ways is food used In the body? 20. Do you understand all parts of this lesson paper? If not, what part is not clear? Note. — After completing the test sign your full name. CHEMISTRY OF THE HOUSEHOLD A Day's Chemistry PART II. CLEANING The cleaning of the dishes, silver, cutlery, and linen introduces a great variety of chemical problems. The subject of the chemistry of cleaning may well include with the daily task of dishwashing, the equally im- portant ones of house cleaning and laundry work. The various processes of housework give rise to many volatile substances, such as the vapor of water or fat. If not carried out of the house in their vapor- ous state these cool and settle upon all exposed sur- faces, whether walls, furniture, or fabrics. This thin film entangles and holds the dust, clouding and soil- ing with a layer more or less visible everything within the house. The fires and lights give out smoky de- posits of incomplete coijibustion. The dishes are soiled with waste from all kinds of foods — starch, grease, al- bumin, milk, gums, or gelatines and the juices of fruits. Dust alone might be removed from most surfaces with a damp or even with a dry cloth, or from fabrics by vigorous shaking or brushing; but usually the greasy or sugary deposits must first be broken up and the dust thus set free. This must be accomplished without harm to the material which is dirty. 56 CHEMISTRY Of THE HOUSEHOLD. Cleaning, then, involves two processes: (i) the greasy or gummy film must be broken up, that the entangled dust and dirt may be set free; (2) the. dust must be removed by mechanical means. We will have occasion to use alkalis for cleaning and acids for removing stains and it will be well to consid- er what is meant by the terms, acid, alkali, and salt. An acid is a substance with an acid or sour taste An ^^^^ and having the property of changing certain vegetable colors. A substance much used in testing for acids is litmus, a kind of fungus, giving a blue solution in water. Paper soaked in litmus solution and dried is known as test paper or litmus paper. It can be bought at any druggist's. This paper is turned red by the presence of any acid, even in the most minute quantity. An acid will cause effervescence with a carbonate like cooking soda or washing soda. ^„ An alkali is a substance often having a soapy taste, Alkali ^ slippery feeling if strong, and the property of turn- ing red litmus, blue. Alkalies will neutralize the effects of acids. If an acid be added very carefully to an alkaline solution, there comes a point where the mixture will change the color of litmus in neither direction. The solution is neither acid nor alkaline, and is said to be neutral. If we make a weak solution of the acid sold at the drug stores as muriatic acid, and add to this very care- fully a weak solution of caustic soda, until the solu- tion is neutral, we shall find that the neutral solution CLEANING. 57 will taste like table salt. In fact, we have made com- mon salt in this way. A chemical salt is a substance obtained by neiitraliz- ^ sait ing an acid with an alkali or otherwise — a substance that is usually neutral and will turn the color of neither red nor blue litmus paper. All acids contain the element hydrogen, which can often be driven out and replaced by a metal placed in the acid. If we drop a bit of zinc into some muriatic acid, tiny bubbles of hydrogen begin to escape. The zinc joins the remainder of the acid, making a new substance. This new substance is the metallic salt, called muriate (or chloride) of zinc. Muriatic acid is also called hydrochloric acid. Thus a salt re- sults from neutralizing an acid with a metal. If oxide of zinc, a white powder, has been used in place of the metal, the same salt, chloride of zinc, would have been made ; but no hydrogen gas would have come off, for the hydrogen of the acid would unite with oxygen of the oxide and form water. Grease or fats, called oils when liquid at ordinary Fats temperature, are chemical compounds made of carbon, ous oxygen, and hydrogen combined in many different ways, but all contain an ingredient of an acid nature known to the chemist as a fatty acid. The fatty acid base is combined with glycerine in the common fats. Strong alkaline substances will break up fats into their parts and combine with the fatty acid, thus making soap. 58 CHEMISTRY OF THE HOUSEHOLD. Alkali '^^^ elements which form strong alkaHs are the Metals "alkali metals." The common elements of this group are sodium and potassium. There is also ammonium which is not an element, but a combination of nitrogen and hydrogen ; it acts, however, like an alkali metal. When an element unites with water in a certain way it is called a hydrate or hydroxide. The hydrate of ammonium — aqua ammonia or ammonia — is known as the ''Volatile alkali" because it evaporates so easily. It is valuable for use in all cleansing operations — in the kitchen, the laundry, the bath, in the washing of delicate fabrics, and in other cases where its property of evaporation, without leaving any residue to attack the fabric or to absorb anything from the air, is in- valuable. Caustic The hydrates of potassium and sodium are called ^°n5 caustic potash and caustic soda, respectively, or the p*oTash caustic alkalis or "lyes" because they "burn" animal tissues. These combine readily with fats to form compounds which we call soaps. Most of the fats are soluble in turpentine, ether, chloroform, naphtha, or kerosene, and somewhat in alcohol. That is, the fats are dissolved unchanged, just as salt is taken up by water. These form solvents for greases more or less valuable according to con- ditions. If the housekeeper's problem were the simple one of removing the grease alone, she would solve it by the free use of one of the solvents or by some of the strong Soap CLEANING. 59 alkalis. This is what the painter does when he is called to repaint or to refinish ; but the housewife wishes to preserve the finish or the fabric while she removes the dirt. She must, then, choose those ma- terials which will dissolve or unite with the grease without injury to the article cleaned. Soap is by all odds the safest and most useful cleaning agent. It is made from most of the common animal and vegetable fats and oils, as tallow, suet, lard, cotton seed oil and cocoanut oil, chemically combined with caustic soda or caustic potash. Castile soap is sup- posed to be made from olive oil. Rosin soap forms a part of all common yellow soap. It lessens the cost and makes a good soap for rough work. Silicate of soda is sometimes added to cheap soaps. It has some cleansing action, but must be regarded as an adulter- ant. Good soaps are nearly neutral substances because the alkali has been neutralized by the fatty acid. The coarser grades may contain more or less free alkali. All soaps are slightly decomposed when dissolved in water. The freed fatty acid produces the milkiness seen when a cake of soap is placed in perfectly pure water. The cleaning action of soaps consists chiefly in forming emulsions with oily or greasy substances. o^ soap Cream is an example of a very perfect emulsion. Its fat is in the shape of very finely divided globules and because of the whey which surrounds them, the cream can be mixed with a very large quantity of water and Action 6o CHEMISTRY OF THE HOUSEHOLD. show no sign of greasiness. When the whey is sep^ arated as in churning, the globules of fat come together and butter is formed. An emulsion is not a true solu- tion, for the particles of fat can be separated by proper means from the liquid. The soap makes an emulsion with the oily or greasy substances holding the dirt, so that both may be washed away by the water. A certain proportion of free alkali in soap helps the action, but it has a cor- rosive effect on many materials. Soap will form emulsions with many other materials besides fats and oils ; so while water is a very general solvent, soap and water will take up many additional substances. Kinds The housekeeper may be familiar with two kinds of jf Soap gQ^p . i^aj.(j soaps and soft soaps. Caustic soda makes the hard soaps and caustic potash makes the soft soaps. Caustic potash is derived from wood ashes and a few generations ago soft soap was the only laundry soap used. Wood ashes were plenty when wood fires were universal. Soda-ash was at that time derived from sea weeds, and therefore uncommon inland. Early in the century a French manufacturer, Leblanc, dis- covered a process of making soda-ash from sodium chloride or common salt. This quite reversed the con- dition of the two alkalis, for now soda-ash is much more common, and the manufacture of soap on a large scale really began then. Soda-ash is now the cheapest form of alkali. Caustic soda is made from soda-ash. CLEANING. 6i The terms, soda-ash, and pot-ash have been used ; soda-Ash these substances in chemical terms are respectively the carbonate of sodium and the carbonate of potas- sium. They are chemical compounds made up of car- bonic acid and two metals — sodium and potassium. When the carbon dioxide, which we have seen is formed by the combustion of carbon, is added to water, carbonic acid results. This is a very weak acid and when it is combined with the very strongly alkaline elements, sodium or potassium, the result is an alka- line substance. Soda-ash and potash (sometimes called pearl-ash) are called alkalis, but they are not nearly so powerful as the hydrates of sodium and potassium which are commonly called caustic soda and caustic potash. When soda-ash, which is a white powder, is dis- washing solved in hot water and the solution is cooled, crystals of the common washing soda are formed. This sub- stance is also called ''sal soda" and "soda crystals." The crystals contain about 65 per cent of water and when exposed to the air, lose some of this water and crumble to the white powder, soda-ash. The powder is, therefore, stronger than the original crystals. Washing soda should never be used in a solid form, but should be dissolved in a separate dish, and the solution used with judgment. A satisfactory amount is about two ounces of the dry soda to a large tub of water, and well dissolved before the clothes are put in. Nearly all of the "washing compounds" on the market Soda 62 CHEMISTRY OF THE HOUSEHOLD. Borax Hard Water Temporary- Hardness Permanent Hardness depend upon the washing soda for their efficiency, and sometimes they contain nothing else. Borax is a useful alkali, milder than washing soda, but effective as a cleaner, disinfectant, and bleacher. It is more expensive than either of the others de- scribed, and because of its weaker alkaline action, more of it must be used to produce a given result. It is much less irritating to the skin and less injurious to fabrics than soda, so for some uses its additional cost may be justified. Caustic potash or *'lye" is too strong an alkali to use on fabrics, but is valuable to put down the kitchen sink drain to free it from grease. The soap made in the drain will be washed out by water. Solid washing soda may be used for the same pur- pose. In the laundry the composition of water is im- portant. Water for domestic use is either hard or soft, according as it contains a greater or less quantity of certain soluble salts — usually compounds of lime or magnesia, which have been taken up by the water while passing through the soil. When the hardness is caused by calcium carbonate (carbonate of lime) it is called ''temporary" hardness, because it may be overcome by boiling. The excess of carbon dioxide is driven off and the carbonate of lime separates out. The same separation is accomplished by the addition of sal soda, borax, or ammonia. When the hardness is due to the sulphates and chlorides of magnesia or lime, it cannot be removed CLEANING. 63 by boiling. It is then known as "permanent" hard- ness. Pubhc water supphes are sometimes softened before delivery to the consumer by the addition of slaked lime, which absorbs the carbon dioxide, and the previously dissolved carbonate separates out. Soft water is needed in laundry work both for cleanness and economy, and water not naturally soft should be softened by boiling or by the addition of the before mentioned substances. When soap is added to the hard water, it is decom- posed by the water, and the new compound formed by the union of the lime and magnesia with the fatty acid of the soap is insoluble, and therefore settles upon any article with which it comes in contact. Until all the lime has been taken out, there will be no action be- tween the soap and the dirt. Therefore, large quanti- ties of soap must be wasted. It has been estimated that each grain of carbonate of lime per gallon causes an increased expenditure of two ounces of soap per 100 gallons,, and that the increased expense for soap in a household of five persons where such hard water is used might amount to five or ten dollars yearly. This ''lime soap," although insoluble in water, will dissolve readily in kerosene or naphtha, for which rea- son, kerosene will be found very effective for cleaning bowls or the bath tub when the surface has become coated from the use of hard water and soap. Hard waters produce certain undesirable effects in cooking processes. The cooking of beans and similar Soap and Hard Water Cooking with Hard Water 64 CHEMISTRY OF THE HOUSEHOLD. vegetables should soften the cellulose and break up the compact grains of starch. It is difficult to cook vegetables in hard water, for the legumin of the vegeta- ble forms an insoluble compound with the lime or magnesia of the water, and the cellulose is softened with great difficulty. Hard water does not readily extract the flavor from tea and coffee, and therefore much more of either must be used to get the desired strength. Dish During this discussion of cleansing agents, let us Washing hope that the breakfast dishes have been soaking in water, after having carefully scraped or "scrapped" so as to save soap in washing and to keep the water as clean as possible. Plenty of hot water and soap with clean, dry towels is the secret of quick and easy work. If the hard water is used, it may be softened for the soap is doing no good unless there is a strong suds. To save the appearance of the hands, use a good white soap, free from alkali, and soften the water with borax. Glass, silver ware, china and kitchen ware take their turn. All should be rinsed in hot water to remove the soap and heat the dishes so that they will drain nearly dry and thus make wiping easy. In the dish washing machine used in large hotels and restaurants, the dishes are simply washed with soapy water and rinsed in very hot water while in such a position that CLEANING. 6S they drain perfectly. They dry completely and re- quire no wiping. Fig. i6. ^na^f'ixa^^^^^^mwitsiiew/ftaiMMf'^^^^^i^miissmKsei^ Fig. 16. Dish Washing Machine Used in Large Hotels and Restaurants. Experiment. Wash a plate and dip it in very hot water, then place it so that all parts will drain. Ob- serve if it dries completely. See if you can wash the dishes in this manner with very little wiping and if time would thus be saved. 66 CHEMISTRY OP THE HOUSEHOLD. structure of Fibres Cotton Wool Linen CHEMISTRY OF THE LAUNDRY If the morning happens to be Monday, the washing is probably in progress in the average American fam- ily. The mistress should understand the chemical principles involved and every detail of the work, in order that the best results may be secured, and that the clothes may not be harmed. The fibres of cotton, silk, and wool vary greatly in their structure and a knowledge of this structure as shown under the microscope, may guide to proper methods of treatment. Fig. 17. The fibres of cotton, though tubular, become much flattened during the process of manufacture, and under the microscope, show a characteristic twist, with the ends gradually tapering to a point. It is this twist, which makes them capable of being made into a firm, hard thread. The wool fibre, like human hair, is marked by trans- verse divisions, and these divisions are serrated. These teeth become curled, knotted or tangled together by rubbing, by very hot water, or by strong alkalies. This causes shrinking, which should be prevented. When the two fibres are mixed, there is less opportun- ity for the little teeth to become entangled and there- fore there is less shrinkage. Linen fibres are much like cotton, with slight notches or joints along the walls. These notches serve to hold the fibres closely together, and enable them to be felted to form paper. Linen, then, will shrink, though ■.03 a QJ H > o [H K Q o 2:; -i-> p o <1 hJ W o •- 1— 1 a PS OS H to w 1^ o a o K o V 1^ H ^ c ^ w s CI) o hr o n K 'tj t>. ^ *- P s "C CS Oj +J CO o a ffi ^ (3 THE LAUNDRY. 67 not so much as wool, for the fibres are more wiry and the teeth much shorter. Silk fibres are perfectly smooth and when rubbed, simply slide over each other. This produces a slight shrinkage in the width of woven fabrics. Cotton and wool differ greatly in their resistance to the treatment of chemi- cals. Cotton is very little affected by a solution of the alkalies, when the cloth is well rinsed. If the alkali is not removed completely, however, it becomes very concentrated when the cloth dries, and as it generally acts for a long time, the fibre may be weakened or ''tendered." Cold dilute solutions of the acids have no very great effect on cotton, provided always that they are com- pletely washed out. Strong or hot solutions of acids have a very decided deleterious action, and even a very minute quantity of acid dried on the goods tenders the fibre badly. Wool resists the acids well, but is much harmed by the action of the alkalies. A warm solution of caus- tic soda or caustic potash will dissolve wool quickly and completely. The carbonates, like washing soda, C D Textile Fibres Much Magnified, a, Wool; b, Mohair; C, Cot- ton; d, Silk; e, Linen. Silk Chemical Action on Fibres o o o o o o o o o o A MECHANICAL WASHING DEVICE Made to fit in the bottom of a wash boiler. The formation of steam forces the hot, soapy water up the spouts, over and through the clothes. SPECIAL IRON HEATER A gas saver. Made as an attachment to a gas stove and as a separate stove on legs. THE LAUNDRY. 69 most needed. The water should be well softened, and a very little extra washing soda solution may be added. The soaking loosens the dirt and saves much rubbing and hence wear on the clothes. It is probable that the cleansing wears out the articles which make up the weekly wash more than the actual use they re- ceive. After washing the clothes, they may be wrung out Boiling and put into a boiler of cold water, which is then heated and boiled briskly for a little while. Whether to boil, or not to boil the clothes depends largely upon the purity of the materials used. If there is any iron in the water, or elsewhere, it is sure to be de- posited on the goods, thus producing yellowness. Soap may be added to the clothes in the boiler, or borax may be used, allowing a tablespoonful to every gallon of water. The borax serves as a bleacher and as an aid in the disinfection of the clothes. One great ad- vantage of boiling is the additional disinfection which this insures. After washing, the clothes should be thoroughly Ringing rinsed. They cannot be clean otherwise and proper rinsing is essential to successful washing. The more thoroughly the wash water is removed between rins- ings, the less number of rinsings will be required to give the same results. Bluing is frequently added to the last rinsing water to counteract, or cover up, any yellowness. A light blue appears to the eye whiter than a light yellow. Bluing 70 CHEMISTRY OF THE HOUSEHOLD. The color is, however, gray in comparison with white. Most of the Hquid bkiing now on the market contains Prussian Blue, a compound of iron. This compound is decomposed by soap and alkalies, when the goods are next washed, making a slight yellow stain of iron on the cloth. Frequent repetitions of this action may give a distinctly yellow shade to the white goods. The indigo blue used a generation or more ago did not have this objection. It is said that white goods which have never been blued, never require bluing. stains Stains and all special deposits should be removed before the goods are treated with soap or soda, as these frequently set the stains. Hot water will spread any grease and also set many stains-, so the clothes when not soaked, should be wet thoroughly in cold or luke-warm water before washing. Washing Colorcd goods and prints require more delicate treat- ^ Goods ment than white goods. If they are soaked, the water should be cold and contain very little soap and no soda. Only dissolved soap should be used in wash- ing them, and this should be of good quality, free from alkali. They should be dried with the wrong side out aftd in the shade, for direct sunlight fades colors about twenty times as much as reflected light. Washing All wool goods rcquirc the greatest care in wash- wooiens .^^^ ^^^^ difl'erent waters used should be of the same temperature and never too hot to be borne comfortably by the hand. Size, GAS-HEATED IRONING MACHINE 37. inches. Price, $40.00. With Electric Motor, $100 SMALL HEATED HAND MANGLE Size, 24 inches. Price, $32.00 A COLD MANGLE Price, $6.75 GENERAL, ELECTRIC COM- PANY FLAT IRON ON STAND Price, $3.50 to $5.00 GASOLINE OR ALCOHOL * IRON Price, $5.00 Soap Solution THE LAUNDRY. 71 The soap used should be in the form of a thin soap solution. No soap should be rubbed on the fabric and only a good, white soap, free from rosin, is allow- able. Make each water slightly soapy and leave a very little in the fabric at the end, to furnish a dressing as nearly like the original as possible. Many persons prefer ammonia or borax in place of the soap. For pure white flannel, borax gives the best satisfaction on account of its bleaching quality. Whatever alkali is chosen, care should be exercised in the quantity taken. Only enough should be used to make the water very soft. The fibres of wool collect much dust upon their srushing tooth-like projections and this should be thoroughly brushed or shaken off before the fabric is put into water. All friction should be by squeezing, not by rubbing. Wool should not be wrung by hand. Either run the fabric smoothly through a wringer or squeeze the water out, that the fibres may not be twisted. Wool may be well dried by rolling the article tightly in a thick dry towel or sheet and squeezing the whole till all moisture is absorbed. Wool should not be al- lowed io freeze, for the teeth will become knotted and hard. Above all, the drying should be accom- plished quickly, and in short, the les? time that is taken in washing, rinsing, and drying, the less will be the shrinkage and the better will be the result. Woolens starching Cooked Starch Uncooked Starch 72 CHEMISTRY OF THE HOUSEHOLD Some of the clothes are starched. This in addition to making them stiffer and giving them a better ap- pearance helps to keep them clean longer. Practically all the household starch on the market is corn starch, although in the textile industries and large laundries, wheat, potato and rice starches are used. Corn starch has the greatest stiffening effect, but wheat starch and rice starch penetrate better and give a more flexible finish. To make cooked starch for ordinary work, wet ^ cup with y^ cup of water and pour on one quart of boiling water. Boil thoroughly till clear. Use double the quantity of starch for stiff starching. Borax may be added — ^ to i level tablespoon to a quart — to in- crease the gloss and penetrability and to prevent the iron from sticking. Lard, wax or paraffine is some- times cooked with the starch for the same purpose — yi tablespoon to a quart. For very stiff starching, as for collars, the thick paste should be rubbed thoroughly into the goods and the excess wiped off with a damp cloth, after which the goods is dried before a fire. The prepared starches, to be used cold, contain borax. This may just as well be added to cheaper preparations. As the uncooked starch depends upon the heat of the iron to swell and stiffen it, a hotter iron is required than with boiled starch. For producing an ecru shade in curtains, coffee is sometimes added in quantity to give the desired color. A solution of gum arable is sometimes used to stiffen A METHOD OF FOLDING DRESSES, SHIRTS AND SHEETS OR TABLE CLOTHS / fr V ^ • \\\\ irrfV' .liaLu "/ C? nVi'i'n^TU /■iVrVl^1-i••y^^) ^ 'nine •.,,-!. ^^ ^■•n|'vrM,pvi^ k:-i.v:.C;:V,j kii^;v•:;^:^^ii bii^^^Ii-^vA l^^j^^^,.^ \ METHOD OF FOLDING UNDERCLOTHES ORDER OF IRONING Night Dresses: 1 — embroidery, 2 — sleeves, 3 — yoke, 4 — body. Drawers: 1 — trimming, 2 — tucks, 3 — body, 4 — band. Skirts: 1— ruffle, 2— hem, 3— body. Shirt Waists: 1 — cuff, 2 — collar band, 3 — sleeves, 4 — yoke, 5 — back, 6 — front. (From "The Laundry," by Flora Rose; Bulletin of tbe Cornell Reading Course for Farmers' Wives, Ithaca, N. Y.) THE LAUNDRY. 1Z dark colored clothes which would show the white color of the starch. THE REMOVAL OF STAIN Whenever possible, stains should be removed when fresh. If the staining substance is allowed to dry on the cloth, its removal is always more difficult, and sometimes a neglected spot or stain cannot be removed without damage to the cloth. The nature of the spot must be known before the best substance to dissolve and remove it can be chosen. To remove grease spots, solvents of grease should be chosen, though w^e may remove such spots some- times by causing the grease to form an emulsion with soap and thus be removed, or the grease may be made into a soap with ammonia or washing soda and thus dissolved and removed in water. The first of the three methods is, as a rule, the best. Grease will dissolve readily in benzine, naphtha, gasoline, kerosene, ether, and chloroform and somewhat in turpentine and hot alcohol. Ether and chloroform are the best solvents, but they are more expensive and not much more ef- fective than naphtha. Caution! All of the solvents for grease are in- flammable and some are explosive, so that they should never be used near a fire or light. Work with them should be done in the day time and preferably out of doors. Grease Spots Precautions A.bsorbents 74 CHEMISTRY OF THE HOUSEHOLD. In applying any of these solvents to grease spots in fabrics, a cloth should be placed underneath the stain to absorb the excess of liquid containing the dissolved grease. The spot should be rubbed from the outside towards the center until dry. This will tend to distribute the solvent and prevent the formation of a ring where the liquid stops. It is well to apply the solvent on the wrong side of the fabric. Old spots of any kind may require long treatment. For this a little lard may be rubbed into the spot and left for some time, then the whole may be dissolved by naphtha or washed out with soap or ammonia. Spots of grease on carpet or heavy material may be treated with absorbents. Heat will assist by melting the grease. Fresh grease spots may often be removed by placing over the spot a clean piece of blotting paper and pressing the spot with a warm iron. French chalk or whiting may be moistened with naphtha and spread over the spot. When all is dry, brush ofif the absorbent. The absorption method may be used in many other cases, moistening with cleansing agent which will not harm the material treated. Biuin Bluing spots may frequently be removed by soak- stains -^^g -j^ strong ammonia water. Alcohol or ammonia will remove grass stains, and an old remedy is to smear the stains with molasses before the article goes into the wash. The acids in the molasses seem to have the desired effect on the grass stains. STAINS. 75 Fresh stains of cofifee, tea or frnit may be removed by hot water. Stretch the stained part over an earth- en dish and pour boiling water upon the stain until it disappears. It is some times better to sprinkle the stain with borax and soak in cold water before ap- plying the hot water. Old, neglected stains of coffee, fruits, cocoa, etc., will have to be treated with some bleaching agent. In many cases, it is not possible to remove them without severely damaging the cloth. Mildew causes a spot of a totally different char- acter from any we have considered. It is a true mold, and like all plants, requires warmth and moisture for its growth. When this necessary moisture is furnished by any cloth in a warm place, the mildew grows upon the fibres. During the first stage of its growth, the mold may be removed, but in time, it destroys the fibres. Strong soapsuds, a layer of soft soap, and pulver- ized chalk, or one of chalk and salt, are all effective if, in addition, the moistened cloth be subjected to strong sunlight, which kills the plant and bleaches the fibres. Bleaching powder or Javelle water may be tried in cases of advanced growth, but success cannot be assured. Some of the animal and vegetable oils may be taken out by soap and cold water or dissolved in naphtha, chloroform, ether, etc. Mineral oil stains are not sol- uble in anv alkaline or acid solutions. Kerosene will Coffee and Fruit Stains Mildew Vaseline Staini 76 CHEMISTRY OF THE HOUSEHOLD. Paint Ink Spots Indelible Ink evaporate in time. Vaseline stains should be soaked in kerosene before water and soap touch them. Paints consist mainly of oils and some colored earth. Spots of paint, then, must be treated with something that will take out the oil, leaving the insoluble color- ing matter to be brushed off. Turpentine is most generally useful. Spots of varnish or pitch may be dissolved by the use of the same solvents as paint. Alcohol is also one of the best solvents here. Spots made by food substances are greasy, sugary, or acid in their nature. Whatever takes out the grease will generally remove the substance united with it, as the blood in meat juices. Sugar is dissolved by hot water, so sticky spots are best removed with this. Ink spots are perhaps the worst that can be encoun- tered, because of the great uncertainty of the composi- tion of inks of the present day. When the character of an enemy is known, it is a comparatively simple matter to choose the weapons to be used against him, but an unknown enemy must be experimented upon and conquest is uncertain. Indelible inks formerly owed their permanence to silver nitrate. Now many are made from aniline black solutions and are scarcely aftected by any chemicals. The silver nitrate inks become dark in the sun by a photographic process. Many silver salts, and some salts of other metals, change in color in a bright light. Ink STAINS. 7T Silver nitrate inks may be removed by bleaching powder solutions. The chlorine in this replaces the nitric acid forming white silver chloride. This will darken if not at once removed, but will dissolve in strong ammonia water or a solution of hyposulphite of soda. This last salt, much used by photographers, commonly called "hypo," will often dissolve the stain of indelible ink without the use of the bleaching fluid and is less harmful to the fibres. Some inks contain carbon in the form of lamp black which is not affected by any chemicals which can be used. The old fashioned black ink is a compound called writing the gallo-tannate of iron. It is made by adding a solu- tion of sulphate of iron to a water solution of nut galls. A little gum solution is added to make the ink of better consistency. This kind of ink is removed by the addition of a warm solution of oxalic acid or muriatic acid drop by drop, and this finally well rinsed out. Of course some materials will be injured by the acids, so this method must be used with cau- tion. Lemon juice and salt will sometimes remove the spot and is safe. Cover the spot with salt, wet with lemon juice, and spread in the sun. Bleaching powder solution and acid will frequently destroy any ink stain of long standing which acids alone will not affect. Some ink stains are removed when fresh by clear, cold, or tepid water — skimmed milk is safe and often effective. If the stain is allowed to soak in the milk Carpets 78 CHEMISTRY OF THE HOUSEHOLD. until the milk sours, the result is often better. Some- times the ink will dissolve out if a piece of ice is laid on the spot and blotting paper under it. The blotting paper absorbs the water and should be often changed. Ink on Ink on heavy materials like carpets and draperies may be treated with some absorbent to keep the ink from spreading. Bits of blotting paper, cotton batting, meal, flour, sawdust, etc., may be used and removed as long as any ink is absorbed, then go over the spot repeatedly with a lemon freshly cut, and finally rinse with cold or tepid water. If an ink stain has worked through varnish into the wood, turpentine will usually remove the spot. Of late colored inks are generally prepared from aniline colors. These are made from substances pro- duced in the distillation of coal tar. The colors are soluble in water, and by dissolving them and adding to the mixture some thickening substance, different colored inks are produced. They are rather difficult to remove successfully, but bleaching powder solution will frequently destroy them. Iron The red iron-Fust spots must be treated with acid. These are the results of oxidation — the union of the oxygen of the air with the iron in the presence of mois- ture. The oxide formed is deposited upon the fabric which furnishes the moisture. Ordinary "tin" uten- sils are made from iron coated with tin, which soon wears ofif, so no moist fabric should be left long in tin unless the surface is entire. Colored Inks Rust STAINS. 79 tron-nist Is, then, an insoluble oxide of iron. The chloride of iron is soluble and so hydrochloric acid is used to remove the rust. The best method of apply- ing the acid is as follows : Fill an earthen dish two- thirds full of hot water and stretch the stained cloth over this. Have near two other dishes with clear water in one and ammonia water in the other. The steam from the hot water will furnish the heat and moisture favorable for chemical action. Drop a little hydrochloric (muriatic) acid on the stain with a medi- Removins Rust FIG. 19. REMOVING IRON RUST STAIN. cine dropper. Fig. 19. Let it act a moment, then lower the cloth into the hot water. Repeat till the stain disappears. RJnse carefully in the clear water and, finally, immerse in the ammonia water, that any excess of acid may be neutralized and the fabric pro- tected. Salt and lemon juice are often sufficient for a slight stain, probably because a little hydrochloric acid is formed from their union. Salt and Lemon Juice 8o CHEMISTRY OF THE HOUSEHOLD. Ink stains on colored goods are often impossible to take out without also removing part of the dye. The ink must be washed out in cold water before it dries ; any slight stain remaining can, perhaps, be removed with a weak acid like lemon juice without harming the color. BLEACHING When the clothes are washed, the mistress likes to have them hang out of doors where the air and sunshine can dry them. She is glad when the white articles can be spread on the grass, knowing that they will be made whiter by Nature's bleaching agent. The sunlight is the chief agent in this bleaching and the articles are laid flat on the grass so that the rays of light will strike in a more perpendicular direction. There are also other devices for bleaching, among which are the fumes of burning sulphur, chloride of lime (bleaching powder) and Javelle water. Originally all bleaching of linen and cotton was done out of doors by the action of oxygen, water, and sunlight. In these days of great factories, this process is impossible for lack of space ; but various artificial bleaching stuffs have been discovered whose action is satisfactory if skilfully used. Bleaching Chloriuc is a gas which has remarkable readiness to combine with other bodies. It is even more energetic than oxygen. By its action upon them, chlorine de- stroys the greater number of coloring substances. Be- BLEACHING, 8i cause of its liarmful action upon the human body, chlorine gas itself cannot be used in factories or in the household, but the compound which chlorine forms with lime (oxide of calcium) known as chloride of lime or bleaching powder, is safe and effective. The principal coloring matters are composed chiefly of the elements carbon and hydrogen and some of the metals = If a substance which makes new combination with the elements present is brought in contact with these colors, the new compounds thus produced may be colorless. The element chlorine does just this. It can be set free from chloride of lime by weak acids, and will dissolve very readily in water when so set free. By dipping colored cloth into a weak solution of chloride of lime and acid, many colors and stains are at once destroyed. But the energy of the chlorine is not stopped by this process. Having destroyed the color, the bleaching powder attacks the fibres of the goods, unles.: the cloth is at once placed in some solution which can neutralize the bleaching powder. There are several such easily obtained and used. The use of bleaching powder in the household is frequently of dubious success for lack of this precaution. Am- monia water will perform this action satisfactorily, since the harmless soluble salt, ammonium chloride, is formed ; hypo-sulphite of soda is also effective. Chloride of lime loses strength rapidly if exposed in an open vessel. It absorbs water and carbon di- Action of Chlorine Chloride of Lime 82 CHEMISTRY OF THE HOUSEHOLD. oxMe from the air, grows damp and the chlorine gas escapes. In using bleaching powder, mix one or two tea- spoonfuls with a pint of cold water in an earthen- ware dish. The effective part of the powder will be dissolved, so let the mixture settle, or strain off the liquid through a cloth. Add a little vinegar or a few drops of acetic acid to the nearly clear solution and use at once. javeiie Javcllc watcr is also used as a bleaching agent. It is Water ^^^^ jjj^^ blcaching powder, except that soda replaces the lime. It is prepared by dissolving one pound of washing soda in a quart of hot water and adding one quarter of a pound of chloride of lime also dissolved in a quart of hot water. Let the mixture settle, pour off the clear liquid and bottle it for use. It will keep for some time. The dregs may be used to scour the kitchen floor or to disinfect waste pipes. This is very useful in removing stains on white cloth, but the addition of some solution to neutralize the action is always necessary, just as with bleaching powder. The best substance to use for this is hypo-sulphite of soda, the "hypo" used in photography, which is quite harmless to the cloth. Sulphur Chlorine cannot be used in bleaching fabrics of ani- Bieiching '^^^^ ^hvQ such as wool and silk ; it leaves them yellow rather than white. For these the fumes of burning sulphur, or these fumes dissolved in water must be BLEACHING. 83 used. No special means of destroying the excess of sulphur fumes i's required. These fumes are a com- pound of sulphur and the oxygen of the air and famil- iar to every one, in the acid fumes from a burning "sulphur match." The article to be bleached must be wet, and then hung in some enclosed space above a piece of burning sulphur. The sulphur candles, to be had at any druggist's, are convenient for this use. Fig. 20. The fumes have great affinity for oxygen, that is, unite with it easily, and take it from the color- ing stuffs, converting them into colorless ones. This method of bleaching is sometimes not permanent. FIG. 20. A SULPHUR CANDLE. These fumes of sulphur are often used to disinfect rooms where there has been sickness. Its power in this respect is far less than is generally supposed how- ever, and much larger quantities of the gas are re- quired for thorough work than are commonly used. Chlorine gas is an excellent disinfectant, but is dan- gerous to use because of its irritating effect upon the throat and lungs. The use of ''chloride of lime" as a disinfectant depends upon the fact that chlorine slowly 84 CHEMISTRY OF THE HOUSEHOLD. escapes from this substance when it is exposed to the air. Hydrogen Another bleaching agent of growing importance Peroxide -^ pej-Qxide of hydrogcn. Water is a compound made up of one-third oxygen and two-thirds hydrogen. Un- der certain conditions, a compound half oxygen and half hydrogen may be prepared. This is not very permanent as the extra oxygen slowly escapes. This extra oxygen has great power as a decolorizer. The peroxide is a liquid much like water in appearance and is used in bleaching hair, feathers, and ivory. It is the safest bleaching agent for the housekeeper to work with and may be used on wool and silk as well as cotton and linen. CLEANING WOODWORK In the interior of the house woods are seldom used in their natural state. The surface is covered with two or more coatings of paint, varnish, etc., which add to the wood durability or beauty. The cleaning processes are applied to the last coat of finish and must not injure this. Soft woods are finished with paint, stain, oil, shel- lac, varnish, or with two or more of these combined ; hardwoods with any of these, and in addition, wax, or wax with turpentine, or both with oil. A:i^-:ie3 AH these surfaces, except those finished with wax, may be cleaned with a weak solution of soap or am- monia, but the continuous use of any alkali may im- in Cleaning CLEANING. 85 pair and finally remove the polish. Refinishing will then be necessary. Waxed surfaces are turned dark by water. Finished surfaces should never be scoured nor cleaned with strong alkalies, like sal-soda, orpotash soaps. Scouring with these strong alkalies will break the paint or varnish and in this way destroy the finish. A few drops of kerosene or turpentine on a soft Kerosene cloth may be used to clean all polished surfaces. The latter cleans them more perfectly and evaporates read- ily ; the former is cheaper, safer, because its vapor is not so inflammable as that of turpentine, and it pol- ishes a little while it cleans ; but it evaporates so slowly that the surface must be rubbed dry each time, or the ^ust will be collected and retained. The harder the rubbing, the higher the polish. Outside the kitchen, the woodwork of the house sel- dom needs scrubbing. The greasy layer is readily dissolved by weak alkaline solutions, by kerosene or turpentine, while the imbedded dust is wiped away by the cloth. Polished surfaces keep clean longest. If the finish be removed or broken by deep scratches, the wood itself absorbs the grease and dust, and the stain may have to be scraped out. CLEANING METALS Most metals may be washed without harm in a hot alakline solution or wiped with a little kerosene. Stoves and iron sinks may be scoured with the coarser materials like ashes, emery or pumice ; but copper, pol- Tarnish 86 CHEMISTRY OF THE HOUSEHOLD. ished steel, or the soft metals, tin, silver, and alumi- num require a fine powder that they may not be scratched or worn away too rapidly. Metal bathtubs may be kept clean and bright with whiting and am- monia, if rinsed with boiling hot water and wiped dry with soft flannel or chamois. Porcelain or soapstone may be washed like metal or scoured with any fine material. The special deposits on metals are caused by the oxygen and moisture of the air, by the presence of other gases in the house, or by acids or corroding liquids. Such deposits come under the general head of tarnish. The metals, or their compounds, in common use are silver, copper and brass, iron and steel, tin, zinc and nickel. Aluminum is rapidly taking a prominent place in the manufacture of household utensils. There is little trouble with the general greasy film or with the special deposits on articles in daily use, if they are washed in hot water and soap, rinsed well and wiped dry each time. Yet certain articles of food act upon the metal of tableware and cooking utensils, forming true chemical salts. The salts of silver are usually dark colored and Sulphide insoluble in water or in any alkaline liquid which will not also dissolve the silver. Whether found in the products of combustion, in food, as eggs, in the paper or cloth used for wrapping, in the rubber band of a fruit jar, or the rubber elastic which may be near the Silver METALS. 87 silver, sulphur forms with silver a grayish black com- pound—a sulphide of silver. All the silver sulphides are insoluble in water. Rub such tarnished articles, before washing, with common salt. By replacement, silver chloride, a white chemical salt, is formed, which is soluble in ammonia. If the article be not washed in ammonia it will soon turn dark again. With an old or deep stain of silver sulphide friction must be used. The analysis of many samples of silver polish, showed them to be made up of either precipitated chalk, diatomaceous earth or fine sand. In using them, it is necessary to be careful in regard to the fineness of material since a few coarse grains will scratch the coating of soft silver. In former times the housewife bought a pound of whiting for fifteen cents, sifted it through fine cloth, or, mixing it with water, floated off the finer portion, and obtained in this way, twelve ounces of the same material for three ounces of which the modern housewife pays twenty-five cents or even more, when she buys it ''by the box." The whiting may be made into a paste with ammonia or alcohol, the article coated with this and left till the liquid has evaporated. Then the powder should be rubbed off with soft tissue paper or soft cotton cloth, and polished with chamois. The presence of water always favors chemical change. Therefore iron and steel rapidly oxidize in damp air or in the presence of moisture. All metallic articles may be protected from such action by a thin Silver Polish Whiting 88 CHEMISTRY OF THE HOUSEHOLD. oily coating. Iron and steel articles not in use may be covered with a thin layer of vaseline. Rust can be removed from iron or steel by kerosene, if not too deep. The tarnish on brass or copper will dissolve in am- monia water, but the objects tarnish again more quick- ly than if polished by friction. TEST QUESTIONS The following questions constitute the "written reci- tation" which the regular members of the A. S. H. E. answer ip. writing and send in for the correction and comment of the instructor. They are intended to emphasize and fix in the memory the most important points in the lesson. CHEMISTRY OF THE HOUSEHOLD. PART II. Read Carefully. Place your name and address on the first sheet of the test. Use a light grade of paper and write on one side of the sheet only. Do not copy answers from the lesson paper. Use your own words, so that your instructor may know that you understand the subject. Read the lesson paper a num- ber of times before attempting to answer the questions. 1. Name all the substances you .can think of which are not soluble in water and are soluble in naph- tha or benzine. 2. Does sugar neutrahze acid chemically? Why? 3. Hovv^ is soap made? What is the difference be- tween hard and soft soap? 4. What is "hard" water? How does it act with soap? How is it softened? 5. Explain how "bluing" may make white clothes yellow. 6. Why remove stains when fresh? Why before washing ? 7. Why is there danger in using naphtha, benzine, and to some extent alcohol near a light ? 80 How do cotton and woolen differ in the effect of acids and alkalies upon them? CHEMISTRY OF T^JE HOUSEHOLD 9. What precautions must be taken in bleaching or removing stains with chloride of lime solution or with Javelle water? 10. Give a good method of starching and ironing clothes. 11. If possible, try to remove some stain by a method given in this lesson and tell of the results. 12. Describe a good method of washing woolens. 13. Why does the drying of a little acid or alkali on a fabric have a very disastrous effect? 14. What is your method of washing dishes ? 15. What can you say of acids, alkalies, salts? 16. What is "washing soda?" How should it be used? When should it no/ be used? 17. Why does strong soap or washing soda harm varnish or paint? 18. What is the cause of tarnish on metals? How can it be removed and prevented ? 19. What advantages has ammonia for use in the laundry ? 20. Do you understand everything given in this les- son paper? Are there any questions you would like to have answered? Note. — After completing the test sign your full name. CHEMISTRY OF THE HOUSEHOLD. A Day's Chemistry. PART III. CHEMISTRY OF BAKING POWDER We will suppose that after the strenuous course of cooking, washing, and cleaning outlined for the morn- ing, that the housekeeper still has strength to make soda biscuits for tea, and we will study the chemical action involved. One of the first chemical methods of securing car- bon dioxide to use in making bread rise, was by putting hydrochloric acid and cooking soda together in a dough which might be put into the oven before the gas es- caped from it. Cooking soda is a salt called bi-carbonate of sodium. cooking It differs from the ordinary mono-carbonate of soda (washing soda) in yielding twice as much carbon diox- ide in proportion to the sodium part of the compound. The saleratus of our grandmother's time was bi-car- bonate of potash, made from wood ashes. The name is still used, but at all stores, cooking soda would be delivered invariably if saleratus were asked for. The true saleratus costs ten times as much as the soda and is no more effective. The carbonic acid is easily set free by chemical compounds of an acid nature, and new chemical compounds result. Soda 90 CHEMISTRY OF THE HOUSEHOLD. Heating Cooking Soda Early Experiments Experiment. Put a little cooking soda into any- acid — lemon juice, vinegar, almost any fruit juice — and the carbon dioxide will be seen to escape in tiny bubbles. Part of the acid unites with part of the soda, forming a new salt, and the acid taste will be much reduced or lost. Part of the carbon dioxide in sodium bi-carbonate is driven off by simply heating, leaving ordinary sodium mono-carbonate, washing soda. In using this process, cooking soda is mixed with the flour. The high temperature of the oven drives off carbon dioxide, and the bread puffs up. It is light, but yellow in color. The sodium carbonate remains in the bread and its alkaline nature serves to neutralize the acid fluids of the stomach (gastric juice) so that digestion of the bread may be retarded. The sodium carbonate also acts in some way upon the gluten producing an unpleasant odor. Among the first methods proposed was one undoubt- edly the best theoretically, but very difficult to put in practice. This depended upon the liberation of carbon dioxide from bi-carbonate of sodium by means of muriatic acid — the method already described. The liberation of gas is instantaneous on the contact of the acid with the ''soda" and even a skilled hand can- not mix the bread and place it m the oven without the loss of much of the gas. Tartaric acid, the acid phos- phates, sour milk (lactic acid), vinegar (acetic acid); BAKING POWDER. 9t alum, all of which hav^ been used, are open to the same objection. Cream of tartar is the only acid substance commonly used which does not liberate the gas by simple con- tact in cold solution. It unites with "soda" only when heated, because it is so slightly soluble in cold water. Experiment. To illustrate this stir a little soda and "cream of tartar" into some cold water in a cup. Ip another cup mix the same amounts of each in warm water. Note the difference in the action produced. To obtain an even distribution of the gas by thorough mixing, cream of tartar would seem to be the best medium by which to add the acid, but because there are other products which remain behind in the bread in using ajl the so-called baking powders, the healthful- ness of these residues must be considered. Common salt is the safest residue and perhaps that from acid phosphate is next in order. The tartrate, lactate, and acetate of sodium are not known to be especially hurtful. As the important constituent of Seidlitz powders is Rochelle salt, the same compound as that resulting from the use of cream of tartar and ''soda," it is not likely to be very harmful, even in the case of the habitual "soda bis- cuit" eater, because of the small quantities taken. The various products formed by the chemical de- composition of the alum and "soda" are possibly the most injurious, as these are sulphates, and are thought Cream of Tartar Injurious Products / 92 CHEMISTRY OF THE HOUSEHOLD. I to be the least readily absorbed salts. 'The sale of "alum" baking powder is increasing, as it is cheaper. / Taking into consideration then the advantage given by the insolubility of cream of tartar in cold water, and the comparatively little danger from its derivative — Rochelle salt — it would seem to be, on the whole, the best substance to add to the soda in order to liberate the gas, but the proportions should be chemically ex- act, since too much alkali would hinder the process of digestion. Hence baking powders prepared by weight and carefully mixed, are a great improvement over cream of tartar and "soda" measured separately. As commonly used, the proportion of soda should be a little less than half. LIGHTING By the time supper is over or even before, during a large portion of the year daylight has gone. Our grandmothers would have brought out the candles. Perhaps we shall use a candle to light our way while we carry the butter and food into the cool cellar. The Candle The caudlc flame although small in area is typical of all flames. Flame indicates the burning of a gas for solid substances in burning simply glow and do not burn with flame. When wood and soft coal burn, gases are set free by heat and these gases burn over the bed of fuel, giving the flames. The o^eneral form of the candle flame is a cone widest above the base, or about at the top of the wick. If it is examined carefully it will be seen to consist Flame LIGHTING. 93 of three layers. Fig. 21. The interior part is dark, giving out no Ught. The second is yellow and is the luminous part, and surrounding this and most easily seen at the base, is a very thin blue layer. Experiment. If a small splint of v^ood or a match be placed across the lower part of the flame near the wick for a moment, it will be charred where the outer layers of the flame have touched it, but the centre will not be changed. Press a piece of card board quickly down on the flame from above and remove it before it is set on fire, and a ring of scorched paper will show the shape of the hot part of the flame. The candle consists of hydro- carbons (compounds of carbon and hydrogen). When a match is applied to the wick, the hydrocar- bons are melted and the liquid rises on the wick by capillary at- traction. The heat changes this to gas (or vapor) which is set on fire, since at the high temperature it easily unites with the oxygen of the air. There is plenty of oxygen present, but it is all seized upon by the carbon and hydrogen in the outer parts of the column of gas rising from the wick, so that none reaches the centre. The gas diffuses outward toward the oxygen continually, so that the inner cone may be regarded as a gas factory. The yel- Fig. 21. Flame of a Candle. 94 CHEMISTRY OF THE HOUSEHOLD. Nature of Smoke Explosions Explosive Mixtures low light is caused by the incandescence or glowing of small particles of carbon, heated to "white heat." These are set free from the compounds where the hame is very hot and they are not yet united with oxygen. Flames "smoke, '^ that is, throw off unburned car- bon when there is an insufficient supply of oxygen. Any device which constantly renews a steady supply of air (with oxygen) will make the flame burn better. The chimney of a lamp does this by protecting the flame from wind and by making, enclosing, and direct- ing upward a current of air. The chimney makes the lamp "draw," as the chimney of the house makes the stove "draw." When the air is mixed with an inflammable gas and the temperature of any part is raised to the kindling point of the gas, as happens if a light is brought into such a mixture, an explosion takes place. The flame spreads through the whole and combination ensues everywhere almost instantly. Great heat is produced and the gases expand suddenly and with violence. If the gases are confined, the enclosing walls may be broken by the pressure. Contraction follows this ex- pansion and air rushes in, producing a second sound. The sounds occur so near together as to give the im- pression of one. In a mixture of inflammable gas and air there must be a certain proportion of each to give conditions which will produce an explosion. A very small amount of gas in the air will not explode under any conditions, LIGHTING. 95 as when there is an odor of coal gas in the room from which no explosion follows even though a light be present. On the other hand, a mixture containing a large proportion of inflammable gas and a little air will not explode. The proportion of air to gas in an explosive mixture varies in different cases, but in gen- eral ranges from about twelve to five parts of air to one Fig. 22a. The Effect of Wire Gauze on a Gas Flame. part of gas'. It is, of course, never safe to rely on the chance of the correct proportions of gas and air not be- ing present. Explosions sometimes occur by unwise use of kero- sene in kindling a fire in a stove. If the kerosene is poured upon a fire already burning, enough vapor of kerosene may be produced to give a disastrous explo- sion. Soaking wood or paper in kerosene for use as kindlings and then lighting would produce no such dire results. 96 CHEMISTRY OF THE HOUSEHOLD. Safety Lamps Kerosene Lamps Explosions in mines are usually caused by a ga« called fire-damp and composed of carbon and hydrogen. When this escapes from the coal and becomes mixed with air, it is very explosive. If a miner brings a naked flame into the mine, the fire-damp will ignite and disaster results. A safety lamp was devised by Davy for use in such dangerous places. It was found that a gas is cooled below its kindling temperature in passing through a fine wire gauze. Lamps surrounded by such a gauze may be taken into a mine with comparative safety. Fig. 22. The action of the wire gauze upon the gas may be studied by holding over a gas jet a piece of fine wire netting, such as is used in window screens, and then lighting the gas above the netting. Fig. 22a. It will be seen that the gas below the netting is very slow in igniting, since it does not readily become sufficiently heated, the wire netting cooling it below its kindling point. The kerosene lamp gives light by the principle already described. The reservoir of the lamp corre- sponds to the cup of melted tallow at the top of the candle. The oil is drawn to the top of the wick by capillary attraction, where the heat vaporizes it ; so that vapor and not oil is what really burns. The struc- ture of the flame is precisely like that of the candle, although its shape differs, because of the shape of the wick. Fig. 22 LIGHTING. 97 Illuminating gas is today the source of light in most city houses. There are two kinds of gas now fur- nished for this purpose. Coal gas is obtained from the destructive distillation of soft coal. Receivers or retorts of iron or fire clay are filled with soft coal and heated to i ioo° or more. From these retorts tubes lead up into a large pipe called the hydraulic main, r\ Service Main FIG. 23. MANUFACTURING OF COAL GAS. through which water is kept flowmg. As the coal be- comes heated, a number of different substances are given of¥, which at this high temperature are in the gaseous state. Some of them dissolve in the water of the hydraulic main, but those needed for illuminat- ing gas are not soluble and passing out of the main, they travel through several hundred feet of vertical pipe called the condenser, where more water removes any impurities which may have escaped from the hydraulic main. Coal Gas 98 CHEMISTRY OF THE HOUSEHOLD. Purifying Coal Gas Aniline Water Gas The gases are then passed on through numerous other devices to remove remaining traces of impurities, and are finally collected in a circular chamber known as the gas-holder, from which they are distributed to the consumer. Fig. 23. If the purification is not perfect, the coal gas will contain sulphur compounds, and these on burning pro- duce oxide of sulphur, which is further changed by moisture and the air into sulphuric acid. The quan- tity produced may be very minute and yet in time may be sufficient to damage books and fabrics. The materials which collect in the hydraulic main and the condensers contain many useful substances, one of the most valuable being ammonia. Among the most interesting substances obtained from coal tar is aniline from which beautiful dyes are made. Aniline itself is a colorless liquid, but in combination with other chemical substances it yields a wide range of beautiful colors now used in dyeing. Other useful substances obtained from the distillation of coal tar are carbolic acid, a disinfectant, and naphthalene which is sold in the form of moth balls. In some cities what is known as water gas forms the basis of the illuminating gas. This is made by passing very hot steam over red hot anthracite cr»al or coke. The oxygen of the water unites with the carbon of the coal, forming carbon monoxide — a com- pound of one part oxygen and one part carbon — and the hydrogen of the water is set free. Both the gases LIGHTING. 99 thus formed will burn, but in burning they produce a colorless flame. It is therefore necessary to mix with them some gases containing much more carbon which will give light when burning. The mixture is stored and distributed like coal gas. This gas is cheaper to manufacture in most locali- ties, but it contains much more carbon monoxide which is a very poisonous gas. Much discussion has arisen as to the safety of using water gas and in some places its manufacture is forbidden by law. The destructive distillation of vegetable and animal life in the depths of the earth, caused by the great heat within the earth, has in some places given rise to petroleum and natural gas. The gas gave a cheap and convenient fuel, but unfortunately the supply is becoming rapidly exhausted. An illuminating gas of growing importance today is acetylene. This is a compound of carbon and hydro- gen and is prepared by the action of water upon cal- cium carbide, which is a compound of carbon and the element calcium. Calcium carbide is manufactured in large quantities at Niagara Falls where pure lime mixed with powdered charcoal is fused at an intense heat. A dark gray crystalline solid results which, when mixed with water, produces acetylene gas and slaked lime. Acetylene is a colorless gas of characteristic odor, soluble in water, and explosive if mixed with air. With an ordinary burner it makes a yellowish smoky Natural Gas Acetylene 100 CHEMISTRY OF THE HOUSEHOLD. Acetylene Generators flame, but with a properly constructed burner, it gives a brilliantly white light, very like sunlight. Colors appear at their true values seen in this light. The flame is an intensely hot one. In acetylene burners the gas escapes through two very minute holes directed obliquely towards each other, as shown in Fig. 24. FIG. 24. ACETYLENE GAS BURNERS. The gas has been somewhat in disrepute because of lack of a suitable arrangement for making and storing it. Many generators are upon the market, it is true, but very few of these are really safe. As soon as a reliable one is obtainable, the gas will be widely used for lighting. It may also be used for cooking, but at present is rather expensive. One form of generator is illustrated in Fig. 25. The calcium carbide in lumps is fed automatically into water as long as the gas is used. When the storage tank is nearly full the supply of carbide is automatically shut ofif. In an- other style, which is also automatic, water is fed on to the lumps of carbide. Both styles have their advo- cates, but the lump feed generator is most generally recommended. The apparatus costs from about $65.00 for a 10 light plant to $300.00 for a 100 light plant. LIGHTING. lOI A cheaper gas than acetylene is gasoline gas, some- times called carburetted air gas because it is com- mon air impregnated with the vapors of gasoline. It burns with a rich, bright flame similar to coal gas and Fig. 25. Acetylene Gaa Generator and Storage Tank. is conducted through pipes and fixtures in the same manner. It may be used in an ordinary gas stove. The gas machine consists of a generator containing evaporating pans, an automatic air pump operated by Gasoline Gas 102 CHEMISTRY OP THE HOUSEHOLD. Oxide of Calcium a heavy weight or by a water motor, together with a regulator or mixer. The general arrangement is shown in Fig. 26, the generator being entirely outside the building in which the gas is used. All such ma- chines require intelligent care, for several disastrous FIG. 2G. OASOLINI^ CAS PLANT. explosions have taken place when such care has not been given to the apparatus. LIME. One of the common chemical substances found about the country house at least is quick lime, used for whitewash and as a deodorizer. The term lime usually means the oxide of the element calcium. Its commonest compound is calcium carbon- ate which is found in nature as limestone, chalk, mar- ble, coral, shells, and several other familiar substances. Calcium is also found combined with sulphur and Quick Lime LIME. 103 oxygen in the compound calcium sulphate, which is the mineral gypsum from which plaster of Paris is made. Bones contain a considerable amount of cal- cium phosphate and egg shells, calcium carbonate. Lime, the oxide of calcium, is made by heating broken pieces of limestone in furnaces called lime kilns. The calcium carbonate as a compound is broken up, carbon dioxide gas being given off and calcium oxide left. This freshly formed oxide is called "quick lime," and when it is exposed to moist air, it attracts water and changes to a form called chemically, calcium hydroxide and, commonly, "slaked lime." Quick lime may be used to dry the air of damp cellars, etc., because of this property. The process of slaking the lime is also accomplished by treating quick lime with water. When this is done, much heat is evolved and the hard lumps crumble to a soft powder and increase consider- ably in bulk. The rise in temperature shows that chemical change is taking ]:)lace. Slaked lime will dissolve slightly in water, yield- ing lime-water. This is a mild alkali and has several ^**®'" household uses. It may be prepared by pouring two quarts of boiling water over about a cubic inch of unslaked lime. Stir it thoroughly and let it stand over night ; in the morning pour off the liquid and treat the sediment with hot water a s(^cond time. When the sediment has again settled, pour off the clear liquid and bottle this. It is mixed with milk and fed to young children and invalids to prevent acidity of the Lime 104 CHEMISTRY OF THE HOUSEHOLD. Mortar and Plaster Hydraulic Cement stomach and make the milk more easily digested. Lime-water and oil form one of the best remedies for burns. The alkali of the lime neutralizes the acid nature of the burn. Mortar is made of slaked lime and sand. When this is spread upon the walls, the lime slowly absorbs carbon dioxide, always present in the air, and changes to carbonate of lime. The water is given off into the air (evaporates) and the mass becomes hard. Of course the surface becomes carbonate sooner than the deeper parts because this has closer contact with the air, and it therefore takes considerable time for all the plaster to harden. The water contained in the mortar soon dries, but while the mortar is becoming hard, more water is continually formed in the chemical pro- cess, so that it requires a long time for the new plaster to become quite dry. It is considered unhealthy to live in rooms with newly plastered walls. This may be because such walls are damp, thus producing damp air, or it may be because the moisture in the walls interferes with the passage of air and other gases through the walls — a process little considered as a rule, but of great importance. Certain varieties of limestone contain other salts, such as magnesium carbonate. Lime made from these does not soften from exposure to the air. It will, however, harden after long contact with water, and such substances are known as cements. Portland cement will harden under water. LIME. lOS Quick-lime is a strong alkali and does the work of such substances. It is used in tanneries in taking hair from hides and also in decomposing fats for mak- ing candles. When dead animal substance is buried in lime, the process of decomposition is greatly hast- ened, probably because the lime unites with all water present while the strong alkali acts upon the fats re- ducing them to soaps of different kinds. Whitewash is simple slaked lime mixed with water. It is very cleansing in its effects and also gives the ap- pearance of freshness and cleanness. When newly ap- plied, it is nearly colorless, for the calcium hydrate is colorless ; this in the air soon changes to calcium car- bonate which is white and opaque. CHEMISTRY AND ELECTRICITY. In most houses electricity is used for operating the door bell, table bell and perhaps the electric gas light- ers. Wei have learned how stored up chemical energy is changed into heat and force in the stove and in the human body ; but in the electric cell, chemical energy is changed into electrical energy. If a strip of pure zinc be placed in a weak solution of acid, no chemical action takes place. Place in the same solution a strip of sheet copper and again no action takes place ; but let the copper and the zinc be brought in contact, or connected by a copper wire, and immediately vigorous chemical action will begin at the surface of the copper plate ; bubbles of hydrogen col- lecting there. This action is as follows : the zinc dis- Whitewash A Voltaic Cell io6 CHEMISTRY OF THE HOUSEHOLD. solves in the acid and hydrogen is set free. This hydrogen travels with an electric current set up in the liquid, passing from particle to particle through the liquid until it reaches the copper. Here the hydrogen stops, but the electric current passes up the copper plate and over the wire to the zinc and down that ^o Leclanche Cell Fig. 27. A Simph' Voltaic Cell. Fig. 28. A Leclanche Cell. the liquid and so on. This arrangement of acid and metals is called a simple voltaic cell. Fig. 27. Other cells are arranged with different liquids and solids to gain various ends, and several cells may be united by wires between the plates to gain additional strength of current. The form of cell often employed to work electric bells is the Leclanche cell. Fig. 28. This consists of a plate of carbon (or a porous cell containing carbon), in place of the copper, a strip or rod of zinc, and a solution of ammonium chloride ELECTRICITY. 107 which takes the place of the acid. The zinc is not affected by the ammonium chloride unless it is con- nected with the carbon, but when there is a circuit for the electricity, a current is generated. The com- mon conductors of the electric current are the metals and carbons. Fig. 29. A Battery of Cells Connected iu Series. The zinc is gradually changed to zinc chloride, at the expense of the ammonium chloride, and after a time bpth the zinc and the ammonium chloride must be renewed. In renewing the battery, the jars should be cleaned out carefully and the zincs renewed if they are completely eaten through. A quarter of a pound of pure ammonium chloride (sal-ammoniac) is dis- solved in enough water to about half fill a jar. When the carbon and the zinc are replaced, this will bring the liquid up to two inches from the top. The jar should not be filled too full. The wires which have been disconnected should be reconnected as before. For bell work the cells are usually connected up "in series," that is, the zinc of one cell is connected to Renewing: Batteriea Oelli i& Series lo8 CHEMISTRY OF THE HOUSEHOLD. Plant Foods the carbon of the next, the outside circuit being estab- lished between the end carbon and end zinc. Fig. 29. If there is a short circuit anywhere in the Hne, that is, if the current has a chance in any way to flow from one wire to the other without going through the bell or other apparatus, the batteries are very quickly ex- hausted. A modification of this cell has been made in which the spaces inside it are filled with some spongy mass in the pores of which the ammonium chlor- ide is held. These may easily be car- ried about without danger of spilling solutions. They are called dry cells and when exhausted cannot read- ily be renewed. PLANTS. Most housekeepers have at least a few house plants and many have gardens which occupy part of the time each day. All foods are directly or indirectly produced by plants and it is well to consider also what food these living things require in their turn. Plants are able to take from the materials forming the crust of the earth and from the air surrounding them all that they need for their life. The leaves of the plants, because of the green substance called Fig. 30. A Dry Cell. PLANTS. 109 Upper Surface ooocdcdcd Bvea.tKin