COLUMBIA LIBRARIES OFFSITE 
 
 HEALTH SCIENCES STANDARD 
 
 HX64074420 
 RA599 B28 The sanitary-chemica 
 
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The Sanitary - Chemical and 
 
 Bacteriological Examination 
 
 of Natural Ice 
 
 AN ADDRESS 
 By EDWARD BARTOW 
 
 Directoi Illinois State Water Survey 
 
 The Natural Ice Association of America 
 
 1 1 6 Nassau Street 
 
 NEW YORK, N. Y. 
 

* 
 
 - THE SANITARY— CHEMICAL AND BACTERIOLOGICAL EX 
 
 :•- AMINATION OF NATURAL ICE. 
 
 J 
 
 By Edward Bartow, Director Illinois State Water Survey. 
 
 DURING the past two or three years the Illinois State Water 
 Survey has been called upon to make some sanitary examina- 
 tions of natural ice. In a few cases we have received, with the 
 ice, samples of the water from which the ice was harvested. The com- 
 parative analyses are especially interesting. I wish every much that 
 there were more analyses to place before you, but the data obtained 
 are enough to warrant some interesting conclusions. 
 
 The analyses made have been arranged in two tables. The first 
 table shows the data obtained by the analyses of the specimens of ice. 
 The second table shows a comparison of the analyses of some specimens 
 of ice with the analyses of the water from which the ice was harvested. 
 
 The determinations made are the ordinary determinations of chem- 
 ical and bacteriological analysis, including turbidity, color, odor, residue, 
 chlorine, oxygen consumed, nitrogen as free ammonia, albuminoid 
 ammonia, nitrites and nitrates, alkalinity, the number of bacteria and 
 gas formers. Some of these tests are of little significance in ice analysis 
 but others have a decided value. 
 
 Turbidity refers to the insoluble matter in suspension. It may be 
 dangerous or harmless. Even if harmless it renders a water or an ice 
 less attractive than a clear water. In only one ice did the turbidity 
 exceed five parts per million and in the one which is reported as greater 
 there is so small a residue that one must conclude that there may have 
 been an error in the work. 
 
 Color refers to colored substances in solution. It is due usually 
 to an extract of vegetable matter. Color is usually harmless, but a 
 colored water or ice arouses suspicion and people will not use it. The 
 color of all of the samples was very low; and in no case would it be 
 detected in an ordinary drinking glass. 
 
 Odor is a descriptive term and is reported as aromatic, earthy, 
 vegetable, etc. Only one of the samples was reported as having a notice- 
 able aromatic odor. Only one of the samples was reported as having 
 a noticeable odor. 
 
 "Residue" comprises the solid matter left on evaporating the 
 water. It includes both organic and inorganic constituents. Unless 
 the quantity is excessive, it does not injure the water for domestic use. 
 Five hundred parts per million is a usual allowance in a drinking water. 
 Ice should have very little residue. The highest residue found in the 
 ice examined was 3-4 parts per million, but in most cases it was less 
 than 10, which is the equivalent of distilled water. 
 
 "Chlorine" refers to the quantity of chlorine in combination with 
 
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metals; for example, sodium chloride (common salt). Chlorine is a 
 constant and considerable constituent of sewage. Unless present be- 
 cause of the presence of salt wells, or the nearness to the sea, etc., its 
 presence in a water is a cause for suspicion. The chlorine in the ice 
 examined never exceeded 3 parts per million. It usually could be 
 determined with difficulty, and could well be reported as "trace." 
 
 The "alkalinity" refers to the soluble carbonates or hydrates, and 
 helps to determine the value of a water for household uses. There 
 should be a very low alkalinity in an ice, as was found to be the case 
 In the specimens examined. 
 
 While they indicate very well the purity of the ice from a physical 
 and chemical standpoint, the tests for turbidity, color, odor, residue, 
 chlorine and alkalinity are of no significance with respect to the hygienic 
 condition of the water. 
 
 In Table 2 are shown analyses of ice and the water from which 
 the ice was taken. A consideration of the degree of purification effected 
 by freezing is quite interesting, from both a chemical and bacteriological 
 standpoint. 
 
 The turbidity, although not high in the original water, is practically 
 eliminated. 
 
 The high color in most of the samples was also eliminated, in two 
 of the cases being reduced from 50 to 0. 
 
 The residue was reduced from 183 to 11, 194 to 10 and 197 to 10 
 respectively. 
 
 The chlorine was reduced from 2.4 to 0, 2.3 to 1 and 3 to .2; the 
 alkalinity from 134 to 1, 144 to 3, 180 to 1. 
 
 The oxygen consumed was reduced, and, in most cases, free and 
 albuminoid ammonia, nitrites and nitrates were greatly reduced. 
 
 Where comparisons of the number of bacteria were made, the 
 purification was very striking. In one case, with 12,000 bacteria in the 
 raw water, there were but 125 in the ice; 520 were reduced to 3, 675 
 to 6, 1,400 to 16, and 4,060 to 22, in every case practically 99% reduc- 
 tion. Gas-forming bacteria were also greatly reduced. 
 
 In the purification of water by freezing both suspended matter and 
 soluble substances are removed. The removal of the suspended matter 
 is explained by the fact that water in freezing solidifies on top. The 
 formation of the coating of ice protects the water from disturbance 
 and enables the particles heavier than water to sink to the bottom. 
 Also in the normal formation of the crystalline ice there is no room for 
 solids between the crystals. This accounts for the decrease in the 
 turbidity and bacteria. 
 
 For the removal of soluble substances we must seek another ex- 
 planation. Let us compare the solubility of the ice with the solubility 
 of soluble substances. Ice is soluble in water at 4 degrees Centigrade 
 
(39.2 degrees Fahrenheit) when the water is at its maximum density, 
 but insoluble in water at degrees Centigrade (32 degrees Fahrenheit). 
 The substances occurring in river and pond waters are, as a rule, soluble 
 to a much greater extent than is their concentration in the rivers and 
 ponds. For example, the least soluble of the common substances 
 occurring in pond waters is calcium bicarbonate. This at degrees 
 Centigrade has a solubility of 700 parts per million. In most of the 
 streams of the United States we find less than 200 parts per' million 
 of residue and hence much less than that amount of any one compound. 
 Before very much calcium carbonate would be taken from the water 
 by the ice, there must be a concentration several times the ordinary 
 concentration in the water. The same is true of other salts. Mag- 
 nesium carbonate is soluble 1,300 parts per million. Calcium sulphate 
 is soluble to the extent of 2,050 parts per million. Magnesium sulphate 
 is soluble to the extent of 257,000 parts per million. Of the salts of 
 sodium, sodium chloride (common salt) is soluble to the extent of 
 55,000 parts per million. Other salts, sodium carbonate is soluble to 
 70,000 parts per million, and sodium bicarbonate to 79,000 parts per 
 million. None of these exist in the rivers and streams of the United 
 States to an extent greater than 200 parts per million. Only in sea 
 water do we find these salts present in sufficient quantities, so that on 
 cooling to zero degrees are they taken out with the ice. Sea water con- 
 tains 3% per cent of salts. The water obtained from the melted ice 
 from sea water is said to be fresh. This, however, has a bitter taste, 
 since but four-fifths of the salts present are removed. 
 
 Nature certainly does its share toward furnishing a pure natural 
 ice. If reasonable precautions are taken so that no ice is obtained 
 from grossly polluted ponds or rivers and the surface of the ice is pro- 
 tected, there need be no difficulty in placing a pure ice on the market. 
 This, I believe, is the aim of this Association, and it can not be too 
 highly commended. 
 
COLUMBIA UNIVERSITY 
 
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 as provided by the rules of the Library or by special ar- 
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