112.5^ 
 
 ^mM)X %mm\% f 
 
 /ItotJg 
 
 BOUGHT WITH THE INCOME | 
 
 PROM THE 
 
 
 SAGE ENDOWMENT 
 
 FUND 
 
 THE GIFT OF 
 
 
 it^nirg IBS, S^se 
 
 
 X891 
 
 /S./f9.j9i 
 
 A ,5Z 9 Q.a - 
 
 
 arV17255 
 
 Practical wojJiiiiiiil 
 
 ^ome.r.in.vers«y t*™^, 
 
 heat tof SkiiSi 
 
 school 
 
 3 
 olin.anx 
 
 ?g?r031 247 814 
 
s 
 
 ;x/i: 
 
M ^ Cornell University 
 VM Library 
 
 The original of tliis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924031247814 
 
HEAT 
 
 WOOLLCOMBE 
 
£on&»tt 
 
 HENRY FROWDE 
 
 Oxford University Press Warehouse 
 
 Amen Corner, E.C. 
 
 (Jlew Sorft 
 
 MACMILLAN & CO., 66 FIFTH AVENUE 
 
Practical Work in Heat 
 
 FOR USE IN SCHOOLS AND COLLEGES 
 
 f-fif.i:i V\r. 
 
 ^'r'hTr.rjTv 
 \ trnrnv 
 
 W. G. WOOLLCOMBE, M.A., B.Sc. 
 
 SENIOR SCIENCE MASTER IN KING EDWARd's HIGH SCHOOL 
 BIRMINGHAM 
 
 O;cfotrb 
 AT THE CLARENDON PRESS 
 
 1893 ' 
 
A- s-s'i^^ 
 
 O;cfor> 
 
 J^B 
 
 PRINTED AT THE CLARENDON PRESS 
 
 BY HORACE HART, PRINTER TO THE UNIVERSITY 
 
PREFACE 
 
 The chief value of a scientific education consists not 
 so much in storing the mind with a large number of 
 facts as in the training of the powers of accurate observa- 
 tion and reasoning, and perhaps one of the best means of 
 attaining this end is a course of Practical Work in Heat. 
 Such a course not only trains the hand and eye, but 
 the necessity for continual precaution and carefulness 
 in manipulation makes it an excellent introduction to 
 practical work in other branches of Physics. All schools 
 which include Science in their curriculum have at least 
 a Chemical Laboratory ; but in many cases Physics is 
 only taught by lectures accompanied by demonstrations 
 by the teacher — doubtless because the cost of apparatus, 
 if multiplied sufficiently to accommodate large classes, 
 would be great. This is not the case with the branch 
 of Physics treated of here. The apparatus required is 
 inexpensive, and such as is herein described may be 
 readily obtained or easily made from the ordinary stock 
 of a Chemical Laboratory. 
 
 The average number of students in the classes under the 
 author's charge is twenty-two. In practical work they are 
 
 A3 
 
VI PREFACE. 
 
 arranged in pairs, and at the beginning of the hour each 
 set receives a sheet of instructions in manuscript, treating 
 of the particular experiment allotted to it. These in- 
 structions now take the more permanent form of print, 
 in the hope that they may be more generally useful. 
 The above method prevents the loss of time which would 
 ensue if each experiment had to be explained viva voce. 
 With the help of the instructions work can be begun 
 at once, and ample time is afforded for the teacher to 
 go round and give any further explanation or help in 
 manipulation that may be needed, the lectures being 
 arranged so as always to be in advance of the practical 
 work. After the experiment is completed and the 
 result passed by the teacher, each student is required 
 to enter into a note-book, kept especially for the 
 purpose, 
 
 (a) The enunciation of the experiment. 
 
 {b) A description of the method, either copied from 
 the sheet of instructions, or, in the case of 
 older students, in their own words. 
 
 (c) A figure, carefully drawn, of the apparatus used. 
 
 (d) Their results in a properly tabulated form. 
 
 This last is essential, as, unless it is insisted on, a 
 great deal of the good effect of the work is lost. 
 
 Most of the experiments described are within the 
 range of boys of fourteen, who often obtain good 
 results, and it is hoped that this book may be found 
 useful also to those who are preparing for higher 
 Examinations in which the subject is required. The 
 
PREFACE. vii 
 
 author begs to acknowledge his indebtedness chiefly to 
 Professor Worthington's Laboratory Practice, and to the 
 book on Heat by Mr. H. G. Madan. Mr. Madan has 
 also kindly revised the manuscript, and made several 
 important suggestions, which have been incorporated in 
 the work. 
 
 King Edward's StnooL, Birmingham: 
 July, 1893. 
 
CONTENTS 
 
 LIST OF EXPERIMENTS. 
 
 Those experiments which are marked with an asterisk (*) are 
 suitable only for older students. 
 
 A. Thermometry. 
 
 ART. PAGE 
 
 1. Corrections to be applied to the reading of a barometer . . i 
 
 2. Correction to be applied to the reading of a thermometer . 2 
 
 3. To compare two thermometers 3 
 
 4. To test the freezing point of a thermometer . . 4 
 
 5. To test the boiling point of a thermometer .... 6 
 
 6. To find the melting point of a solid [Directly] ... 6 
 
 7. To find the melting point of a solid [By a time-curve'] . 7 
 *8. To find the melting point of an alloy 8 
 
 9. To find the boiling point of a liquid [ffypsometer Method] . 9 
 
 10. To find the boiling point of a liquid [£7-^«i}^ .A^Moifl . . 9 
 *ii. To compare the variation of the boiling point of a saline 
 
 solution with the degree of concentration .... 10 
 
 B. Expansions. 
 
 12. To find the coefficient of linear expansion of a solid . 12 
 
 13. To find the coefficient of cubical expansion of glass by the 
 
 specific gravity bottle 13 
 
 '14. To find the coefficient of cubical expansion of a solid [Mat- 
 
 thiessen's Method] .... . . '5 
 
 *I5. To find the coefficient of cubical expansion of glass by the 
 
 weight thermometer 16 
 
 *i6. To find the coefficient of cubical expansion of a solid by the 
 
 weight thermometer 18 
 
 17. To find the coefficient of cubical expansion of a liquid by the 
 
 bulb-tube 19 
 
 18, To determine the variation of the coefficient of cubical expansion 
 
 of water at different temperatures by the bulb-tube . 30 
 
X CO NTENTS. 
 
 ART. PAGE 
 
 19. To find the coefficient of cubical expansion of a liquid by the 
 
 weight thermometer .21 
 
 20. To find the coefficient of cubical expansion of mercury by the 
 
 specific gravity bottle . . ^ 22 
 
 "21. To find the coefficient of cubical expansion of a liquid 
 
 \MatthiesserC s Metho<I\ .... . . 23 
 
 22. To find the coefficient of cubical expansion of a liquid {Dulong 
 
 and Petit's Method] 24 
 
 23. To find the change of volume produced on the melting of a 
 
 solid. . 25 
 
 24. To determine the temperature at Vfhich virater has the maximum 
 
 density 26 
 
 25. To find the coefficient of cubical expansion of air at constant 
 
 pressure [Gay Lussac's Method] 27 
 
 26. To find the coefficient of cubical expansion of air at constant 
 
 pressure \Regnaulfs Method] . . . . . .28 
 
 27. To find the coefficient of increase of pressure of air at constant 
 
 volume . . . . . 2Q 
 
 C. Calorimetry. 
 
 2S. To find the water value of a calorimeter and thermometer 33 
 
 29. To find the specific heat of a solid [Method of Mixtures 1] . 33 
 
 30. To find the specific heat of a solid {Method of Mixtures 2] 35 
 
 31. To find the specific heat of a solid [.5/ofi'j jl^^Ao^ . . 35 
 
 32. To find the specific heat of a liquid [Method of Mixtures 1] 36 
 
 33. To- find the specific heat of a liquid [Method of Mixtures 2] . 37 
 
 34. To find the specific heat of a liquid [Method of Mixtures 3] 37 
 
 35. To find the specific heat of a liquid [Method of Cooling] . 38 
 
 36. To determine the amount of heat absorbed when a salt is 
 
 dissolved in water -39 
 
 37. To find the heat of fusion of ice . . 40 
 
 38. To find the heat of fusion of a solid [Method 1] . . 41 
 *39. To find the heat of fusion of a solid [il/c^Aorf 2] . 41 
 
 40. To find the heat of vaporisation of Water . 42 
 
 41. To find the heat of vaporisation of Alcohol 43 
 
 D. Evaporation. 
 
 *42. To determine the pressure of Alcohol vapour at different 
 
 temperatures ... 44 
 43. To determine the pressure of water vapour at different 
 
 temperatures below 100° C . ... 45 
 
CONTENTS. xi 
 
 ART. PAGE 
 
 44. To determine ' the pressure of water vapour at different 
 
 temperatures above 100° C -47 
 
 45. To find the dew-point by Regnault's Hygrometer ... 49 
 
 46. To find the constant of the wet and dry bulb Hygrometer . 50 
 *47. To determine the mass of one litre of Laboratory air . . ji 
 
 E. Radiation. 
 
 48. To investigate the truth of Newton's Law of Cooling • sa 
 
 49. To plot the cooling curve of the Calorimeter . . -53 
 *5o. To compare the emissive powers of different substances 55 
 
 Appendix A 56 
 
 Appendix B . -58 
 
PRACTICAL WORK IN HEAT. 
 
 ERRATA 
 
 Page 23, line 7 from bottoni,/o?- a read a^ 
 
 Page 28, line 12 from bottom, /or {t^-h) read {t^ -it) 
 
 Page 43, line 6 from top, for 70° read 50° 
 
 Page 44, line 3 from bottom, ^or/ read pi 
 
 nvjignt-eoTTCLtcti lor me expansion or me scale is /i {j.+bi). 
 
 {b) Since the density of mercury at o°C is 1 + 6/ times greater 
 than its density at /°, where S is the mean coefficient of absolute 
 expansion of mercury between 0° and f, the column of mercury 
 at 0° representing the atmospheric pressure would be 1 + 8/ 
 times shorter than the column at t°. Our reading therefore is 
 too high, and the height h(j.+bt) corrected for the expansion of 
 the mercury is 
 
 ^^i±^ = h{i +bf) (I + 6/)-' = -4 (I - [8-<5] /), nearly. 
 
 If the scale is of brass 3='00ooi89, and taking the coefficient 
 
 of expansion of mercuryS to be -00018, this expression becomes 
 
 A (i — -00016/). 
 
 ' Or of glass if the scale is etched on the glass tube itself. 
 B 
 
PRACTICAL WORK IN HEAT. 
 
 A. Thermometry. 
 
 1. Correction for barometer readings. 
 
 The standard barometer is graduated when both the scale 
 and the mercury are at o°C, so that we ought always to reduce 
 our reading, h, of the barometer at the temperature, t, of the 
 room to what it would be if the scale and the mercury were 
 at o°C. 
 
 (a) Each unit length of the scale at f is longer than it would 
 be at o° by i + bt, where b is the coefficient of linear expansion 
 of the metal scale ^ Our reading h is therefore too low, and the 
 height corrected for the expansion of the scale is h (i + 3/). 
 
 (3) Since the density of mercury at o° C is i + 6/ times greater 
 than its density at f, where 8 is the mean coefficient of absolute 
 expansion of mercury between o° and f, the column of mercury 
 at 0° representing the atmospheric pressure would be 1 + 8/ 
 times shorter than the column at i°. Our reading therefore is 
 too high, and the height h{i+bf) corrected for the expansion of 
 the mercury is 
 
 ^i^ = A (I +bt) (1+8/)-^ = h (I -[6-3] /), nearly. 
 
 If the scale is of brass 3=-ooooi89, and taking the coefficient 
 
 of expansion of mercury 6 to be -0001 8, this expression becomes 
 
 ^(i — -00016/). 
 
 ^ Or of glass if the scale is etched on the glass tube itself. 
 B 
 
c' Practical Work in Heat. 
 
 {c) There are two other corrections to be made : one for the 
 index error, which is merely the mistake of the maker ; the other 
 for capillarity, which depends on the diameter of the tube. 
 These two corrections are made once for all for a given 
 barometer and must be added to all reduced observations. 
 
 Example. On a day, when the temperature was 15°, the 
 height of the barometer was 754-3™™. Reduce this reading 
 too". 
 
 The reduced height is 754-3 [i— -00016 x 15]= 752-49 
 Capillarity and index error = -24 
 
 Corrected height= 752-73 
 
 2. Correction for thermometer readings. 
 When the whole of the thread of mercury in a thermometer 
 is not immersed in the substance whose temperature we are 
 measuring, the thermometer reading is somewhat too low, and 
 we must apply a correction to it to give us the true temperature 
 of the substance. 
 
 Suppose T° the true temperature of the substance, 
 
 t° the temperature indicated by the thermometer, 
 t°' the mean temperature of the air near the thermo- 
 meter, 
 / the length of the projecting thread. 
 If the whole of the mercury were at the temperature T, the 
 length / would become /[i + A {T—i')], where A is the coeflS- 
 cient of relative expansion of mercury. If n is the number of 
 degrees in unit length, the number of degrees in the length / 
 is nl, or N suppose. Therefore, at t", N would become 
 ^[i + A(r— /')], that is, the thermometer reading would be 
 increased by N^ (T—t'), 
 
 .-. r=/+^A{7'— /'), 
 
 or 
 
 r= ^^"^^ = {t-Nt^f) (i -ivA)-' = /+ A^A (/-/'), nearly, 
 
 where A = -000155. 
 
 Example. Find the true temperature of water when a thermo- 
 
A. Thermometry. 3 
 
 meter, immersed up to the 20**1 degree, shows a temperature 
 of 80-3°, while the temperature of the surrounding air is 16-7°. 
 
 T= 8o-3 + 6o-3X-oooi65(8o-3— 16-7) 
 = 80.89°. 
 
 3. Comparison of two thermometers. 
 
 It is often convenient and sometimes necessary to use two 
 thermometers in an experiment, and, as mercury thermometers 
 seldom exactly agree, it is important to compare one with the 
 other. 
 
 Apparatus. Two tHSrmometers : Beaker : Sand-bath : Retort- 
 stand and Clamp : Bunsen Burner : Curve-paper ". 
 
 Experiment. Tie the two thermometers together and support 
 them by the clamp so that they dip vertically into a beaker of 
 water placed on a sand-bath. Heat the water gradually, keeping 
 the whole of it well stirred ' continually. About every five 
 degrees rise of temperature take the readings of each ther- 
 mometer*- Enter the corresponding temperatures in two 
 adjacent columns. Continue taking readings until the water 
 boils. 
 
 Plot a curve of your results as follows: — Take a piece of 
 curve paper and draw two straight lines at right angles to 
 each other near the lower and the left-hand edges of the 
 paper. These lines are called the axes of the curve, and the 
 point of their intersection the origin. Along the bottom line 
 [the line of abscissae] mark off equal spaces to represent 5°. 
 The number of divisions on the paper to be taken to 
 represent 5° must depend (a) on the number at your dis- 
 posal and (b) on the range of temperature to be indicated. 
 Along the left-hand vertical line [the line of ordinates] 
 mark off equal spaces [not necessarily of the same length as 
 before] to represent 5°. Along the horizontal line place very 
 
 * See Appendix B. 9. 
 
 ' Stirring is a most important opeiation where uniformity of temperature 
 is required. A feather or a flat piece of wood does well for a stirrer. 
 
 * In reading a thermometer place your eye on a level with the top of the 
 mercury thread, and always estimate to tenths of a degree. A pocket 
 magnifying glass is useful for the purpose. 
 
 B 2 
 
4 Practical Work in Heat. 
 
 small dots at the points representing the temperatures you have 
 read on thermometer A, and along the vertical line at the points 
 representing the temperatures read on the thermometer B. Now 
 mark with a very small cross the points obtained by the inter- 
 section of imaginary vertical lines through the temperatures of A 
 with imaginary horizontal lines through the correspohding tem- 
 peratures of £. Draw carefully a fine continuous line [curved or 
 straight as the case may be] which will pass through the average 
 run of the series of points so obtained ^ The points along 
 this curve represent also those which we have not determined 
 by experiment. We can now easily find what temperature on 
 one thermometer corresponds to a given temperature on the 
 other. For, if we wish to know what temperature on B 
 corresponds to 55-5° on A, draw a vertical line through the 
 point representing this temperature on A, and from the point 
 where this line intersects the curve draw a horizontal line. 
 This will cut the vertical temperature line of B at the required 
 point. Fig. I shows a curve obtained by comparing two given 
 thermometers. 
 
 4. Test freezing point of a thermometer. 
 
 Apparatus. Funnel: Beaker: Thermometer: Retort-stand: 
 Ice. 
 
 Experiment. Place the funnel in a ring of the retort-stand 
 and under it place the beaker. Hang the thermometer with its 
 bulb inside the funnel so that the zero is on a level with the 
 rim. Well wash a piece of ice and with a chisel scrape off some 
 shavings. Pack these round the thermometer in the funnel. 
 Pour over them some distilled water and determine the lowest 
 point to which the mercury sinks. The difference between this 
 point and o° will be the zero error of the thermometer. 
 
 » The cnrve will not pass through all the points unless your observations 
 have been perfectly exact. Some points will probably be above and some 
 below the final cnrve. It is a good thing to use a piece of thin cardboard 
 or a flexible lath as a guide when tracing the curve. When a curve is 
 completed, always write along the top edge of the paper the experiment 
 to which the cnrve refers, and along the horizontal and vertical axes the 
 name of the measurements to which their corresponding divisions refer. 
 
A. Thermometry. 
 
 41 -U-X - .. ___ ^ 
 
 ds 1 ' ■ / 
 
 
 
 ■ 1 /\ 
 
 -^ ' i i ,i- _ jX 
 
 an -4 ■ Ml _ iZZjZ 
 
 
 I'll / 1^ X 
 
 1 ■ , 1 J rr 
 
 - , ■ '1 -------- - jf 
 
 
 
 , 1 ' ■ ! " J 1 
 
 
 
 7r ' M ' 'T"iT^ 
 
 ZS ^ U_ _ J M ' • 1 
 
 + -^^+- ^ H- - -y~^ . T^ 
 
 / ■ i ■ t ]■" ^ 
 
 ' r , ■ ' 1 
 
 65- V ' ' ' M ' ' ' 1 
 
 
 
 
 ' ' 1 A ' 1 ' ' ' 
 
 rti 1 '■ I / ',''.', 
 
 
 1 I/' ! i 1 ' i ' 1 1 1 ■ ! ' 
 
 
 /' ■ 1 ' ' ' ' ' ' 1 
 
 ; ; ■ i : j' ; 1 M , ; , 1 1 ' : ! ! ' ' ' 1 ! 1 
 
 I X ' '/ 1 ' M 
 
 
 J^ » 1 /\- ' ' i 1 , ' 1 , 
 
 
 rd" E -S / ' ' ' ' ! I ' I 1 ■ 1 
 
 
 fe s ' V/ ' ' • M ' i 
 
 ■V? '/ r'' 
 
 •^' \ ' A ' ' ' 'iiiii 
 
 4=" "^ ~ ' ' /! ' 1 i : ' ' ; , 1 : 
 
 
 i » / ' 1 ^ , ' 1 ' 
 
 :S ? - v' M M i ' 
 
 =? ^ > '1 
 
 <n ' ^ ' ! : ■ 1 1 1 1 1 i 1 
 
 
 *T» 5 !' 1 ' i ! 1 r 1 ' 1 
 
 ■ = '^ / ' ' ! i 1 ' i 1 1 ■ i ' ' 
 
 ■■ ■=. .1 ' ! M 1 r ' ' ' ' 1 ! i 
 
 T? TT ' J ' . 1 h - ' ' ■ ; 
 
 'I'' a J, ' '■ ■ ■ ' ■ 1 1 
 
 = S J • 1 1 , ! . 
 
 " ■■ -^ i- ' 1 ' 1 1 ' ' 1 
 
 i I'll! 
 
 ,'?>-*- -1^ r 1 M 1 M M 1 ' 
 
 
 """""" 1 ' 1 ■ ■ ' 
 
 
 -/<• -•- 111:!;' 
 
 33 J 1 1 i 1 
 
 io -- / M ' ■ ' 
 
 
 -XX f ^ ' ' 1 ! ' 1 1 ■ ' '1 
 
 
 -Jnl 1 V i i 1 1 1 
 
 ^0- i 1 - 1 11 1 1 1 : ' ■ 1 : 
 
 ix j' " I ' 1 ■ 
 
 / , 1 ■ ' ' 1 
 
 X 3 " , : 1 i ' 1 1 
 
 
 i5 t 1 1 1 1 ■ ' 1 1 ■ ' ' 1 t 
 
 J -J_ ,-^ ' i ' ; ' ' ' 'ill 
 
 d' it " 1 
 
 / ' ■ ' 1 ' 
 
 i^i -^ ^ i ' ■ ■ ■ 1 ■ ■ 
 
 i' " J ■ "' ■■ 1 1 ' 1 ■ 1 1 ' M ' t ' ' 
 
 h-^ / 1 1 1 1 1 ' 1 1 1 1 ! 1 ! 1 
 
 
 r -- ;" ■ ^j u , : , 1 1 1 . 
 
 '1 / L 1 1 ' 1 ■ 
 
 
 
 
 
 /i 1 1 1 1 ! i 1 < 1 1 
 
 
 
 Fig. I. 
 
6 Practical Work in Heat. 
 
 5. Test boiling point of a thermometer. 
 
 Apparatus. Flask fitted with a two-holed bung : Short elbow- 
 tube : Thermometer : Sand-bath : Bunsen Burner. 
 
 Experiment. Fill half the flask with water. Fit the elbow-tube 
 into one hole, the thermometer into the other hole of the bung. 
 Arrange the thermometer so that, on placing the bung in the 
 flask, the bulb is about i cm. above the surface of the water. 
 Place the flask on the sand-bath and apply heat. When the 
 water has boiled briskly for some time, and the thermometer has 
 risen as far as it will, read the temperature. This gives the 
 boiling point under the present atmospheric pressure. We must 
 now correct for the difference between this and the standard 
 pressure of 760™™. From the table giving the boiling points 
 under different pressures [Appendix A. 10] we find that a differ- 
 ence of 1° in the boiling point corresponds to a difference of 
 pressure equal to 26-8""». Therefore, if x" is the required 
 correction, 
 
 26-8 : 760 — barometric height :: 1° : x°. 
 
 Example. A thermometer marks 99'3° as the boiling point 
 of water when the height of the barometer is 755-5™™. Find 
 the error of the thermometer. 
 
 26-8 : 4-6 :: i°:j;°; .-. .ar = -17°, nearly. 
 
 Thermometer reading = 99-3 
 
 Correction 
 
 = 
 
 • 17 
 
 Error of boiling point 
 
 = 
 
 99-47 
 
 ■53 
 
 loo-oo 
 
 e. Determination of the melting point (Method 1). 
 
 Apparatus. Glass tube drawn out to a fine bore: Beaker: 
 Test-tube: Thermometer: Sand-bath: Bunsen Burner : Paraffin- 
 wax. 
 
 Experiment. Melt the wax in the tegt-tube and draw up 
 some of the liquid into the narrow glass tube. Fuse the end 
 and tie it to the thermometer and support vertically in a beaker 
 
A. Thermometry. 7 
 
 of water placed on the sand-bath. Heat the water, keeping it 
 continually stirred. Note the temperature at which the wax 
 begins to be transparent. Take away the burner and allow 
 the water to cool. Note the temperature at which the wax 
 begins to solidify. The mean of the two readings will give the 
 melting point approximately. Lower the flame and heat very 
 gently, so as to determine the melting point as above more 
 accurately. Repeat this twice more and take the mean of the 
 results as the true melting point. 
 
 Determine as above the melting points of Beeswax and Stearic 
 Acid. 
 
 7. Determmatioii of the melting point (Method 2). 
 
 Apparatus. Test-tube fitted with a two-holed cork : Beaker : 
 Thermometer : Sand-bath : Retort-stand : Watch : Bunsen 
 Burner : Paraflin-wax : Curve-paper. 
 
 Experiment. Fill the test-tube with the melted wax and fix 
 the thermometer" in the cork so that it dips into the melted 
 wax up to the 20'^'^ degree or so. Support the test-tube by a 
 string to the retort-stand and bring up a beaker of water to 
 immerse it completely. Heat the water till the wax is all 
 melted. Take away the beaker, wipe the test-tube dry, and 
 allow the wax to cool gradually. Note the temperature indicated 
 by the thermometer every half minute until the wax has become 
 quite solid and has cooled to about 30°. Arrange your results 
 in a tabular form as follows : — • 
 
 Times. 
 
 Temperatures. 
 
 
 
 Plot your results in a curve taking the times as abscissae and 
 the corresponding temperatures as ordinates. As the liquid 
 
 ' The thermometer ought previously to be warmed carefully over a flame 
 to prevent its breaking when placed in the melted wax. 
 
8 
 
 Practical Work in Heat. 
 
 gives out its latent' heat on solidifying the temperature will for 
 some time remain more or less stationary at this point. There- 
 fore the curve will show two turning points. The line between 
 them is approximately parallel to the axis of times, and, if pro- 
 duced, will cut the axis of temperatures at the required melting 
 point. Compare your result with that of Experiment 6. 
 
 Determine as above the melting points of Beeswax and 
 Stearic Acid. 
 
 
 f 
 
 / 
 
 Fig. a. 
 
 *8. Determination of the melting point of an alloy. 
 
 \A is a cylindrical vessel of sheet iron, 
 3 cm. in diameter, 6 cm. in height. In the 
 middle of it is 6xed a metal tube B, i cm. in 
 diameter. Between A and B is the alloy. 
 The tnbe B contains mercury, the level of 
 which is just above that of the alloy.] 
 
 Apparatm (Fig. 2). Thermometer: 
 Watch : large Bunsen Burner : Mercury : 
 Common Solder [equal parts by mass 
 of Lead and Tin] : Curve-paper. 
 
 Experiment. Fill the outer cavity of 
 the apparatus about three parts full 
 with the alloy and the inner cavity rather more than three 
 parts full with mercury. Close the central tube with a loose 
 cork through which a thermometer passes so that the bulb 
 dips under the mercury. Heat this vessel up to about 22o°C 
 so as to completely melt the alloy. Take the burner away and 
 allow the vessel to cool. Read the thermometer every mirmte 
 until the alloy has become quite solid. Arrange your results in 
 a tabular form and plot a curve as in Experiment 7, and notice 
 the difference between the two curves. In this case there are 
 four turning points, which is explained by supposing the alloy 
 to consist of two distinct alloys, whose chemical compositions 
 are diflFerent and which melt at different temperatures. After 
 raising the temperature above the melting point of the less 
 fusible and allowing it to cool this one solidifies, first giving out 
 its latent heat. On cooling further the temperature is attained 
 
A. Thermometry. 9 
 
 at which the other component solidifies. The alloy that gives 
 
 two turning points only is called the ' chemical alloy ' of the 
 
 two component metals. 
 
 Determine as above the melting points of the following 
 
 alloys : — 
 
 I part by mass of Tin and 3 parts by mass of Lead (270°)'', 
 I part by mass of Lead and 3 parts by mass of Tin (200°)'. 
 
 8. Setermination of the boiling point (Method 1). 
 
 [A is a boiling tube 3 cm. in diameter. Through 
 the cork passes air-tight a^maller test-tube B, about 
 2 cm. in diameter, which has a hole fused in its side 
 at a. Through the cork of the test-tube pass a 
 thermometer T and an elbow-tube C, one end of 
 which is close to the bulb of the thermometer.] 
 
 Apparatus {¥\g. ^). Thermometer: Bunsen 
 Burner: Methyl Alcohol. 
 
 Experiment. Put some methyl alcohol in 
 the outside boiling tube and fit the apparatus 
 together as in the figure. On boiling the 
 liquid the vapour fills the larger vessel and 
 passes through the hole a to the bottom of the 
 inner one and then up through the tube C. 
 The thermometer will rise : note the tem- 
 perature indicated by it when it becomes 
 quite stationary. This will be the boiling 
 point of the liquid under the existing atmo- 
 spheric pressure. Enter the temperature and the barometric 
 height. 
 
 Determine as above the boiling points of Turpentine and 
 Benzol. 
 
 10. Determination of the boiling point (Method 2). 
 
 [Take a piece of glass tubing about '£ cm. in diameter and 25 cm. in 
 length. Clean and dry it carefully. Close one end by the blow-pipe and 
 bend it as in the figure, making the closed limb about "j cm., and the 
 elbow-piece at the open end about 3 cm. in, length. Introducing some 
 
 ' These are the temperatures to which the alloys must be raised re- 
 spectively. 
 
 Fig. 3- 
 
lO 
 
 Practical Work in Heat. 
 
 Fig- 4- 
 
 clean dry mercury we can, by a little manipulation, fill all the tube with it 
 excepting the short elbow-piece. Then fill the elbow-piece completely 
 with the liquid whose boiling point we require. Close the tube with the 
 finger, and turning it slowly over, allow about 
 .5 cub. cm. of the liquid to pass to the closed end. 
 If there is an air bubble present, transfer the liqnid 
 back again to the elbow- tub^ add^ drop or two 
 more and repeat the above process. Having got 
 the liquid into the closed end free from air 
 bubbles, we have now to get mercury out from 
 the longer limb until its level is about 2 cm. 
 below the top of the closed limb. This may be 
 done by putting the tube into a beaker of water 
 and carefully heating it. Sufficient mercury, as it 
 rises in the longer limb, can be got rid of by 
 a judicious jerk.] 
 
 Apparatus (Fig. 4). Beaker : Thermo- 
 meter ; Sand-bath : Bunsen Burner. 
 
 Experiment. Support the apparatus in a beaker of cold water 
 so that the shorter limb is completely immersed, and place 
 a thermometer close to it. Gradually heat the water, keeping 
 it continually stirred. The pressure of the vapour of the liquid 
 in the tube will increase and will depress the mercury in the 
 shorter limb. When the level of the mercury is the same in 
 the two limbs the pressure of the vapour is equal to the 
 atmospheric pressure. When this is the case, note the tempera- 
 ture by the thermometer. On taking away the burner the 
 mercury in the right-hand limb may continue to rise for a little. 
 If so, allow the water to cool and take another reading of the 
 thermometer when the two columns return to the same level. 
 Repeat this twice more, and take the' mean of your readings as 
 the boiling point of the liquid under the existing atmospheric 
 pressure. Record both the temperature and the ' barometric 
 height. 
 
 Determine as .above the boiling points of Turpentine, Ether 
 and Carbon Bisulphide. 
 
 *11. Variation of the boUing point with the strength 
 of a saline solution. 
 
 Apparatus. A large flask fitted with a cork through which 
 
A. Thermometry. 
 
 II 
 
 pass a short elbow-tube and a thermometer ; Sand-bath : Bunsen 
 Burner : Crystallised Calcium Chloride : Curve-paper. 
 
 Experiment. Drop a small piece of clean coke into the flask 
 to prevenj: boiling with bumping and counterpoise the flask and 
 cork. Put ^bout 20 grams of the salt into the flask and find 
 exact mass of salt, m^, added. Fill the flask about one-third full 
 of distilled water, and arrange the thermometer with its bulb 
 immersed in the liquid. Boil this solution and note the boiling 
 point /j. Weigh the flask so as to determine the mass, M^, 
 of the solution. Add |J)out 20 grams more of the salt. Weigh 
 again to determine exact mass, m^, added. Boil and note the 
 boiling point 4. Weigh to determine the mass, il/j, of the 
 solution. Repeat this process until the boiling point rises to 
 about 150°. Read the barometer and enter your results in a 
 tabular form as follows : — 
 
 Mass of 
 salt added. 
 
 Mass of 
 
 contents of flask 
 
 after boiling. 
 
 Percentage of 
 solid in 
 solution. 
 
 Boiling point. 
 
 TO, 
 
 «3 
 
 Mi 
 M, 
 
 
 
 Barometric pressure, . . , mm. 
 The composition of crystallised Calcium Chloride is 
 CaCl,-h6HjO 
 HI -I- 108 = 319, 
 therefore the mass of solid present is -^^ths of the mass of 
 the salt added. To get the numbers in the third column let us 
 find ir,. The mass of salt added is w, + /«„-(- ot„ therefore the 
 mass of solid present is \\\ (m^ + «Ka + m^- Thus the percentage 
 of Calcium Chloride in the contents of the flask is 
 
 III (Wi+ Wg + Ws) 
 
 219x^^3 
 Plot a curve, taking the percentages as abscissae and the 
 
 X 100. 
 
la 
 
 Practical IVork in Heat. 
 
 corresponding boiling points as the ordinates, marking the origin 
 of temperatures ioo°. 
 
 N.B. At certain stages of the experiment, it may be well to 
 concentrate the solution by boiling the water away instead of by 
 adding more salt. 
 
 Determine as above the variation of the boiling point with 
 solutions of Potassium Nitrate and df Sodium Chloride '- 
 
 B. Expansions. 
 
 The coefficient of linear expansion is that length by which 
 I cm. of a substance expands on being heated i°C. 
 
 The coefficient of cubical expansion is that volume by which 
 I cub. cm. of a substance expands on being heated i°C. 
 
 12. Determination of the coefS.cient of linear expan- 
 sion of a metal tube °. 
 
 \^M'\% the metal tube, about 120 cm. in length, firmly fixed at one end by 
 a short piece of metal rod passing through a slot .S fixed in the wall. Near 
 the other end, which rests on a fixed support, is soldered the needle N. 
 Through the cork, closing this end, passes a piece of glass tubing, connected 
 by india-rubber tubing with an elbow-tube, passing tightly through the cork 
 of the boiling can B ".] 
 
 Apparatus (Fig. 5). Microscope with a divided scale in the 
 eyepiece : Thermometer : Bunsen Burner. 
 
 ° In the case of anhydrous salts add about 10 grams each time. 
 
 ° I believe this method is due to my predecessor, Mr. A. D. Hall. 
 
 " An ordinary oil can, through the cork of which passes an elbow-tube, 
 is a convenient boiling can. Cans made of copper last much longer than 
 the tin ones, as rust eats holes into the bottom of the latter. 
 
B. Expansions. 13 
 
 Experiment. Measure the distance, Z, between the fixed end 
 and the needle, and note the temperature, /, of the room. 
 Arrange the microscope as as to focus an edge of the needle on 
 one of the extreme scale-divisions in the eyepiece, remembering 
 that the direction of the motion of the needle, when the rod 
 expands, is reversed by the microscope. When once adjusted 
 be careful not to move the apparatus during the experiment. 
 Now boil the water in the can and allow the steam to pass 
 through the tube. The tube will expand, and the needle will 
 be seen to move across the scale. Continue to pass the steam 
 until the needle comes •quite to rest. Count the number of 
 scale divisions the needle has moved over and multiply by the 
 known value of a scale division '"■ in centimetres. This gives us 
 the length, /, by which the tube has expanded. Read the 
 barometric height, and find from the tables [Appendix A. 10] the 
 temperature, T, of boiling water at this pressure. Then 
 
 Z cm. have expanded by / cm. for a rise of temperature (2"—/)° 
 
 [t° suppose] 
 
 .•. I cm. expands by — cm. for a rise of i°C, 
 
 which is the required coefficient of linear expansion of the 
 tube. 
 
 Determine as above the coefficients of linear expansion of 
 Iron, Copper and Brass. 
 
 13. Determination of the cubical expansion of glass by 
 the specific gravity bottle. 
 
 Apparatus. Specific Gravity bottle : Beaker : Thermometer : 
 Sand-bath : Bunsen Burner : Mercury. 
 
 Experiment. Thoroughly clean and dry '' a specific gravity 
 bottle. Counterpoise it" and then fill it with Mercury, being 
 
 " This is easily obtained by looking through the microscope at a metre 
 rule and noting how many millimetres are covered by the scale. The scale 
 in use in the writer's laboratory covers 2 mm. and is divided into 100 
 divisions. 
 
 " See Appendix B. 4. ' 
 
 " Bullets, shot, and sand are convenient to counterpoise bodies with. 
 
14 Practical Work in Heat. 
 
 careful not to handle it more than absolutely necessary. Find 
 the mass, M, of the mercury it contains. Place the bottle in a 
 bealser of water whose temperature, /, must be noted. Heat 
 the water till it boils. Read the barometer and refer to the 
 tables [Appendix A. lo] to get the boiling point, T, of the water 
 under this pressure. Take out the~ specific gravity bottle care- 
 fully and dry it. Weigh it again to determine the mass, M', of 
 mercury remaining in it. The mass of the mercury that has 
 been expelled is M-M', or m suppose. The mercury, on cool- 
 ing to t°, would contract and leave a space representing the 
 volume of the expelled mercury. Hence it is evident that 
 M' grams of mercury at f would, on being heated to T°, 
 expand by an amount represented by m grams and fill the 
 bottle. We may take these masses as proportional to the 
 volumes, hence 
 
 M' cub. cm. of mercury expand by m cub. cm. for (T—if 
 
 [t° suppose] 
 
 171 
 
 :. I cub. cm. expands by — ,- cub. cm. for i°C. 
 
 This gives us the mean coefficient of expansion of mercury 
 (A) relative to glass between these temperatures. The co- 
 efiicient of expansion of glass (^) may be taken approximately 
 as the mean real coefl5cient (6) less the relative coefficient of 
 expansion of mercury. 
 
 Look in the tables [Appendix A. 2] for the mean real co- 
 efficient of expansion of mercury between J" and t°, and from it 
 subtract the above value of A in order to get the coefficient of 
 expansion of the glass, and enter your results as follows : — 
 
 M = ... grs. Barometric height . . . mm. T-= ...° 
 m'— ... grs. / = ...° 
 
 /«=... grs. Tables give 6 = . . 
 
 A = ^=... 
 M't 
 
B. Expansions. 15 
 
 *14. Determination of the cubical expansion of a 
 solid by Matthiessen's method. 
 
 Apparatus. A balance " with a hole bored in the base under 
 one of the pans : a small piece of the Solid in the form of a 
 tube or thin sheet [e. g. a piece of glass tube] : Beaker : Ther- 
 mometer : Bunsen Burner. 
 
 Experiment. Hang the solid to one arm of the balance by 
 a very fine wire, passing through the hole in the base of the 
 balance, arranging it so that it can dip into a beaker of water. 
 Counterpoise the solid. Bring up a beaker of water so as to 
 immerse it completely, being careful not to let it touch the sides. 
 Remove any air bubbles from it by a feather, and note the 
 temperature, /, of the water. Restore equilibrium by known 
 weights, coj . This represents the weight of an equal volume of 
 water at /". If V is the volume of the soUd and di the density 
 of water at t°, we have 
 
 Vd, = a,j. (i) 
 
 Now immerse the solid in hot water and allow it to remain for 
 a minute or so until it is of the same temperature as the water "- 
 Determine this temperature, T, and quickly restore equilibrium 
 by known weights, coj. 
 
 If X is the coeflBcient of expansion of the solid, its volume has 
 now become V{i + xt), where t ={r— t)° ; and, if </y is the 
 density of water at 7^, we have 
 
 V{l+XT)dT =0^^. (2) 
 
 Dividing (i) by (2) we get 
 
 di o)j _ 
 
 {l+XT)dT ~ Oil' 
 
 "^i^t — oiidx 
 •'• •* = J ' 
 
 tOj Tar 
 
 Referring to the tables (Appendix A. i) for the densities of 
 water at t° and T° we can find x. 
 
 Repeat the experiment twice more, raising the water each 
 
 " It is best, if possible, to have the balance at a sniBcient height from the 
 table to allow the beaker to rest on a sand-bath over a burner. By adjusting 
 the flame of the burner we can keep the water at a fairly constant tempera- 
 ture while weighing. 
 
i6 Practical Work in Heat. 
 
 time to a higher temperature. Enter your results in a tabular 
 form and compare your values of x. 
 
 Determine as above the coefficients of expansion of Glass, 
 Copper and Zinc. 
 
 *15. Determine the cubical expansion of glass by the 
 weight thermometer. 
 
 Apparatus. A piece of fairly thick glass tubing about 15 cm. 
 long and i"5 cm. in diameter: Beaker: Thermometer: Evapo- 
 rating Dish : Crucible : Retort-stand : Bunsen Burner : Mercury. 
 Experiment. Clean and dry the glass tube. Hold it in the 
 flame of a Bunsen's burner and heat it near one end, keeping 
 on turning it round so as to heat it uniformly. When qtite 
 viscous draw it out while still in the flame and so close the end. 
 Anneal it by holding the closed end in an ordinary gas flame 
 until it is covered by a deposit of carbon and allowing it to cool 
 gradually. 
 
 When it is cool, heat it uniformly near the other end, 
 and when viscous take it out of the flame and draw it out 
 to a fine tube. Bend it as in the figure, and 
 cut off' with a file any superfluous tube. 
 Counterpoise this weight thermometer. Then 
 support it by a wire so that its beak dips 
 under the surface of clean dry mercury [Ap- 
 pendix B. 5j in an evaporating dish resting 
 on a ring of the retort stand. We have now 
 to fill the thermometer with mercury. This 
 \^^ we do by heating it so as to drive out some 
 
 Fig. 6. *''^' ^"'^ ^^''^ allowing it to cool again '^ 
 
 when the atmospheric pressure will force 
 some mercury in. When, by alternately heating and cooling, 
 we have got it about three parts full, boil the mercury so as to 
 expel all the remaining air, and allow the thermometer to remain 
 with its beak still under the mercury until it has cooled down 
 
 " We must be careful -to prevent the glass cracking by the contact of the 
 cold mercury and the heated glass. The sides and not the bottom of the 
 thermometer had better be heated first and the mercury in the dish warmed 
 as well. 
 
 \ 
 
B. Expansions. 
 
 17 
 
 nearly to the temperature of the room. Then bring up a beaker 
 of cold water so that as much as possible of the thermometer is 
 immersed, resting the beaker on another ring of the retort-stand. 
 By means of a siphon change the water three times at intervals 
 of five minutes. While this is going on counterpoise the 
 crucible. We have now the thermometer full of mercury at the 
 temperatiu'e, /, of the water, which we note. Take away the 
 dish containing the mercury and replace it by the counterpoised 
 crucible, so that it may catch any of the liquid that may be 
 expelled from the thermometer. Now heat the water about 10° 
 above the temperature of the room ", keeping the water well 
 stirred; note the temperature, /], and weigh the mercury ex- 
 pelled, m.y Replace the crucible and heat ag^in 10° higher: 
 weigh the total quantity of liquid in the crucible, m^ : continue 
 alternately heating and weighing thus till the water boils. Then 
 take out the weight thermometer, dry it carefully, and find the 
 mass, M„, of the mercury it contains. Enter your results in 
 a tabular form as follows : — 
 
 
 
 Mass of , 
 mercury in 
 weight ther- 
 
 Mean 
 
 Mean 
 
 Coefficient 
 
 Tempera- 
 tures. 
 
 Mass of 
 
 mercury 
 
 in crucible. 
 
 relative ex- 
 pansion of 
 mercury. 
 
 absolute 
 
 expansion of 
 
 mercury. 
 
 of expan- 
 sion of 
 glass. 
 
 
 
 
 <A) 
 
 (S) 
 
 (S-A=A) 
 
 / 
 
 
 M 
 
 
 
 
 '. 
 
 OT, 
 
 M, 
 
 A, 
 
 Si 
 
 ^, 
 
 h 
 
 OT2 
 
 M, 
 
 A, 
 
 5^ 
 
 k. 
 
 U 
 
 m„ 
 
 Mn 
 
 A„ 
 
 s„ 
 
 K 
 
 Mean = 
 
 The numbers in the third column are obtained thus: the 
 
 " Each time before taking the crucible away we must be sure the mercury 
 is at the same temperature as the water. To ensure this regulate the flame 
 so as to keep the temperature fia.irly constant for a minute, keeping the 
 water well stirred. Before removing the crucible it is advisable to touch 
 the beak of the weight thermometer with its side to detach any liquid 
 adhering to the beak by capillary, attraction.. 
 
 C 
 
j8 Practical Work in Heat. 
 
 mercury contained in the weight thermometer at the beginning, 
 M, is equal to i)/„ + M„, 
 
 .-. M=M„+m„, 
 
 M^ = M — »?jj, 
 &c. 
 To get the numbers in the fourth column let us find \\ 
 M^ c.c. of mercury evidently expand by m^—m^ c.c. for {i^—t^, 
 
 .: I c.c. expands by — ".7 ' . c.c. for i°, which is Aj, the 
 
 mean coefficient of relative expansion between // and /^ (see 
 Experiment 13). The numbers in the fifth row are found from 
 the tables (Appendix A. 2). The coefficient of expansion of glass 
 is found by subtracting the corresponding numbers in the fourth 
 and fifth rows. Take the mean of the results, and find the 
 probable error (Appendix B. i). 
 
 N.B. If we assume the coefficient of expansion of glass 
 known, we can by the above experiment determine the absolute 
 coefficient of expansion of mercury. 
 
 *16. Determination of the cubical expansion of a solid 
 by the weight thermometer. 
 
 Apparatus. A piece of fairly thick glass tubing about 15 cm. 
 long and i cm. in diameter: Beaker: Thermometer: Eva- 
 porating Dish : Crucible : Retort-stand : Bunsen Burner : 
 Glycerine : Leaden Shot. 
 
 Experiment. Close one end of the tubing in the flame, and 
 introduce a known mass, M^, of shot. Draw the other end out 
 and bend as in Experiment 15. Weigh and determine the 
 mass of the glass vessel. Fill it in the manner described in 
 Experiment 15, using glycerine instead of mercury, being care- 
 ful to get rid of all air bubbles. After it has attained the tem- 
 perature, /, of the water in the beaker, replace the evaporating 
 dish by a previously counterpoised crucible. Heat the water to 
 boiling and continue boiling for five minutes, so that the shot 
 may attain the temperature of the water. Note the barometric 
 height, and hence determine the temperature, T, of boiling 
 
B, Expansions.-' i$ 
 
 water. When no more glycerine is expelled weigh the crucible 
 and determine the mass, m, of the glycerine in it. Then take 
 the weight thermometer out of the water, dry it, and determine 
 the mass, M^, of the glycerine remaining in it. 
 
 On raising the temperature through (T—/)°, t° suppose, the 
 lead, glycerine, and glass have expanded, and the volume of the 
 expelled glycerine evidently is equal to the sum of the expanded 
 volumes of the lead aftd the glycerine less the expanded volume 
 of the glass vessel. 
 
 If Z), is density of Lead and x its coefficient of cubical expan- 
 sion, • 
 if Dj is density of Glycerine and a its coefficient of cubical 
 
 expansion, 
 and if A is the coefficient of cubical expansion of the glass, then 
 the volume of the Lead taken is 
 
 M, 
 
 — i = Kj c.c, suppose, 
 
 and the volume of the Glycerine that filled the weight thermo- 
 meter at /° is M +m 
 
 —^ = Tj cc, suppose ; 
 
 .■. the volume of the glass vessel at /° is f^-t- y^ c.c, and the 
 
 volume of the expelled Glycerine is 
 
 m 
 
 — = » c.c, suppose. 
 
 Therefore 
 v{i+ar)= V^{i+XT)+V^{i + aT)-{F^+y^){i+kT), 
 
 All the quantities on the right-hand side being known, we 
 can determine x. 
 
 Determine as above the coefficients of expansion of iron and 
 copper, both in the form of filings. 
 
 17. Determinatiou of the cubical expansion of a liquid 
 by the bulb-tube. 
 Apparattts, A long tube of narrow bore with a bulb at one 
 
 c 2 
 
30 Prdtdical Work in Heat. 
 
 end. (The tube must be graduated in equal divisions and the 
 volume of the bulb and of a division must be known [Ap- 
 pendix B. 2.]) Beaker: Thermometer: Sand-bath: Bunsen 
 Burner: Turpentine. 
 
 Experiment. Fill the bulb and a small portion of the tube 
 with turpentine and support it in a beaker of water resting on a 
 sand-bath. Read the temperature, t, of the water and the total 
 volume, V, Occupied by the turpentine. Heat the water, keep- 
 ing it continually stirred, up to a temperature at which the tur- 
 pentine nearly liUs the tube. Lower the flame and when the 
 temperature has become constant read it, 7'° suppose, and 
 note the total volume, V', occupied by the turpentine. It is 
 evident that the original volume, V, has expanded by {y"— V), 
 V suppose, for a rise of temperature (7"—/)° [r° suppose]. 
 .*. V c.c. expand by v c.c. for r°, 
 
 V 
 
 .\ I c.c. expands by — c.c. for 1°, 
 Vt 
 
 which is the mean coefficient of relative expansion of tur- 
 pentine between the two temperatures. 
 
 To get the mean coefficient of absolute expansion add to this 
 the coefficient of cubical expansion of glass. 
 
 Determine as above the coefficients of expansion- of glycerine 
 and alcohol. 
 
 18. Determination of the cubical expansion of water 
 at diflferent temperatures by the bulb-tube. 
 
 Apparatus. A bulb-tube similar to the one used in Experi- 
 ment 17, containing water instead of turpentine: Beaker: 
 Thermometer : Sand-bath : Bunsen Burner : Curve-paper. 
 
 Experiment. Support the bulb-tube in a beaker of water on 
 a sand-bath. Read the temperature, /, of the water and the 
 total volume, V, occupied by that in the tube. Heat the water 
 gradually, keeping it well stirred, and at about every five degrees 
 rise in temperature read off the total volumes occupied by the 
 water in the tube as well as the corresponding temperatures ". 
 
 " To ensure that the liquid is at the temperature indicated, when it has 
 Tieen heated nearly to the temperature required, lower the flame so as to 
 
B, Expansions. 
 
 a I 
 
 Continue this until the water nearly fills the whole of the 
 tube : enter your results in a tabular form as follows : — 
 
 Temperatures. 
 
 Total volumes 
 occupied by 
 the water. 
 
 Relative 
 
 . expansion 
 
 of I c.c. 
 
 t 
 h 
 
 V 
 
 I 
 ft 
 
 To get the numbers in the third column divide those in the 
 second column by V, which will give us the volumes at the 
 diflferent temperatures which i c.c. at t° would occupy. 
 
 Plot your results on a curve taking the temperatures as 
 abscissae and the numbers in the third column as ordinates. 
 What does the form of the curve show you ? 
 
 19. Betermination of the cubical expansion of a Uqmd 
 by the weight thermometer. 
 
 Apparatus. Weight thermometer as in Experiment 15: 
 Beaker: Thermometer: Evaporating Dish: Crucible: Retort- 
 stand : Bunsen Burner : Glycerine. 
 
 Experiment. After counterpoising the weight thermometer 
 ■fill it with glycerine according to the instructions of Experi- 
 ment 15. When the glycerine is at the temperature, /, of the 
 water replace the evaporating dish by a previously counter- 
 poised crucible. Heat the water, stirring continually, until it 
 boils. Note the barometric height and determine the boiling 
 point, T. Remove the crucible Hand find the mass of glycerine, 
 m, that it contains. Take 1 out* the weight thermometer, dry it, 
 and find the mass, M, of glycerine remaining in it. This 
 glycerine would, on being cooled to t°, contract, and would 
 leave a space representing the volume of the expelled glycerine. 
 
 keep the temperature fairly constant for a minute. Now take the reading 
 of the thermometer and the volume of the liquid. 
 " See Note 16. 
 
22 
 
 Practical Work in Heat. 
 
 Hence M grams of glycerine at f, on being heated to r°, would 
 expand by an amount represented by m grams and would fill 
 the weight thermometer. Taking, as we may, these masses as . 
 proportional to the volumes, 
 
 M c.c. of glycerine expand by m c.c. for {T—t)°, [r° suppose] ; 
 
 .•. I c.c. expands by — c.c. for i", 
 
 '^ Mr 
 
 •which gives us the mean coefficient of relative expansion be- 
 tween these temperatures. To get the mean absolute expansion 
 add the coefficient of cubical expansion of glass. 
 
 Determine as above the coefficient of expansion of turpentine. 
 
 *20. SetermirLation of the cubical expansion of mercury 
 at difTerent temperatures by the specific gravity bottle. 
 
 Apparatus. Specific gravity bottle : Beaker : Thermometer : 
 Sand-bath : Bunsen Burner : Mercury : Curve-paper. 
 
 Experiment. Thoroughly clean and dry the specific gravity 
 bottle. Counterpoise it and then fill it with clean dry mercury 
 [Appendix B. 4, 5], and find the mass, M, of the liquid. Place 
 the bottle in a beaker of water, whose temperature, /, we note. 
 Heat the water, stirring continually, until the temperature has 
 risen about 10°. When the mercury is at the temperature of 
 the water ", read the thermometer, /, take the bottle out, dry it, 
 and find the mass, M^, of the mercury in it. Repeat this series 
 of observations for about every 10° rise in temperature until the ' 
 water boils. Read the barometer and find the boiling point, T, 
 and enter your results in a tabular form as follows : — 
 
 Tempera- 
 tures. 
 
 Mass of 
 mercury 
 in bottle^ 
 
 Mean 
 
 coefficients 
 
 ,X>f relative 
 
 expansi&. 
 
 Mean 
 coefficients 
 of abspl'ite 
 expansion. ' 
 
 Expansion 
 of I c.c. 
 
 t 
 
 M 
 
 A, 
 
 8, 
 
 I 
 
 ft 
 ft 
 
 " See Note 17. 
 
B. £-xpansions. a j 
 
 In order tp^the numbers in the third column let us find Aj. 
 M^ CJt. expand by M^—M^ c.c. for a rise in temperature (/j— /J", 
 
 /. I C.C. expands by '"" ' c.c. for i°, which is Aj, the mean 
 
 coefficient of relative expansion of mercury between these 
 
 temperatures. The numbers in the fourth column are obtained 
 
 by adding the coefficient of cubical expansion of glass to those 
 
 in the third column. 
 
 The numbers in the fifth column are found by dividing 
 
 into M the series of numbers in the second column : e. g. 
 
 iWj at f expand to M at /° ; 
 
 M 
 .'. I c.c. at /° expands to — [i.e. /3j] at /,°. 
 
 Plot a curve of your results, taking the temperatures as 
 abscissae and the numbers in the fifth column as ordinates, 
 and compare this curve with the similar one for water obtained 
 in Experiment i8. 
 
 "'21. Determination of the cubical expansion of a liquid 
 by Matthiessen's method. 
 
 Apparatus. The balance used in Experiment 14: A piece 
 of glass tubing about 4 cm. long: Beaker: Thermometer: 
 Bunsen Burner : Glycerine. 
 
 Experiment. Proceed in a similar manner to that described 
 in Experiment 14, and find the loss of weight of the glass tube 
 when immersed in glycerine at different temperatures. If V is 
 the volume of the glass tube and dt the density of glycerine 
 at t°, and tOj the loss of weight, 
 
 Vdt=:(0. (i) 
 
 On heating the glycerine to T°, if k is the known coeflScient 
 of expansion of the glass, dr the density of glycerine at T", and 
 a>2 the loss of weight of the glass in this case, 
 
 V{i+iT)dT = a>^. (2) 
 
 Dividing (i) by (2) we have 
 
 dt (Oj 
 
 {l+kT)dT Wj 
 
24 
 
 Practical Work in Heat. 
 
 
 If X is the mean absolute coefBcient of expansion of glycerine 
 d( = drii + xt) ; 
 
 I+XT _ (Uj _ 
 
 i + kr a>^' 
 _._ ,,._ tOi(i+^r)-a)a 
 
 Repeat the above twice more, raising the glycerine each time 
 to a higher temperature. Enter your results in a tabular form 
 and compare your values of x. 
 
 Determine as above the coeflBcients of expansion of Turpentine 
 and Amyl Alcohol. 
 
 22. Determination of the cubical expansion of a 
 liquid by Dulong and Fetit'a method. 
 
 [A and B are two glass tubes, about 
 .75 cm. in internal diameter and 80 cm. in 
 length, bent at right angles at the bottom 
 where they are joined tightly together by 
 a piece of india-rubber tubing R. B passes 
 through two corks, closing the ends of a 
 -wide glass tube C about 3 cm. in diameter, 
 and nearly but not quite as long as B. 
 Through these corks also pass two elbow 
 tubes D and E — the upper one is con- 
 nected with a boiling can (see note 10) 
 and the lower one is to allow the escape 
 of the steam. This apparatus should be 
 fixed by pieces of leather to a wooden 
 support.] 
 
 Apparatus (Fig; 7). Thermometer : 
 Boiling can : Bunsen Burner : Amyl 
 Alcohol. 
 
 Experiment. By a piece of india- 
 rubber tubing fit the elbow tube D 
 to the boiling can. Hang a ther- 
 mometer, by the tube A. Pour in 
 amyl alcohol coloured by a little 
 carmine so that it stands about 60 
 above the horizontal tube. Arrange the lower tube so that 
 Pass steam through the jacket C, placing 
 
 Fig. 7. 
 
 cm 
 
 it is quite horizontal. 
 
B. Expansions. 35 
 
 a vessel under £ to catch the condensed steam. Pass the 
 steam for some time until the liquid in S has finished expand- 
 ing. Read the height, ff, of the liquid in B and the height, 
 h, of that in A above the top of the horizontal tube. Read 
 the temperature, /, by the thermometer hanging near A. Note 
 the barometric height and determine the boiling point T. 
 
 Now the height ff at T" balances the height A at /°, so that, if 
 the height A were heated to T", its length would become ff. 
 Therefore, if x is the mean absolute coefficient of expansion of 
 the liquid, 
 
 A{i+xt) = //, where t° = {T- if, 
 H-h 
 At 
 
 Determine as above the coefficients of expansion of turpen- 
 tine and glycerine. 
 
 23. Determination of the change of voliime on melting. 
 
 Apparatus. A piece of glass tubing about 25 cm. lolig : 
 Beaker : Thermometer : Buhsen Burner : Mercury : Wax. 
 
 Experiment. Draw out one end of the glass tube to a 
 
 point, and calibrate about 6 cm. of it from the other end 
 
 [Appendix B. 3]. Counterpoise it and introduce through the 
 
 pointed end a column of about 6 or 7 cm. of melted wax. 
 
 Allow this to solidify and fuse the end with a blowpipe. If 
 
 there is any air remaining melt the wax again and drive the air 
 
 out by heat. Find the mass, M, of the wax introduced and look 
 
 M 
 in the tables for its density, D: then its volume is — (or v) 
 
 cub. cm. Now pour into the tube some clean mercury until its 
 level is about 5 cm. from the top. Immerse the tube in a beaker 
 of water on a sand-bath so that all the wax is under the surface 
 and support a thermometer near it. Heat the water, keeping it 
 well stirred, up to the known melting point of wax. Directly it 
 begins to melt read the level, h^, of the mercury. Lower the 
 flame and continue heating and stirring till the wax has all just 
 melted. Read the level, Al, of the mercury again. This change 
 of level represents a known change of volume Wj. Take away 
 
26 
 
 Practical Work in Heat. 
 
 the burner and allow the wax to solidify. When it has just all 
 solidified read the level of the mercury. Repeat this twice 
 more : enter your results in a tabular form and take the mean 
 change of volume as the correct result. 
 
 Xevel of mercniy when wax has 
 
 
 melted. 
 
 solidified. 
 
 Change of volume. 
 
 
 
 
 Average 
 
 Original volume, V = ... c.c. 
 
 Percentage change of volume on melting = ...%. 
 
 Find the probable error of the results (Appendix B. i). 
 Determine as above the change of volume of Stearic Acid 
 and of Ice on melting. 
 
 24. Determination of the temperature of the maximum 
 density of Water. 
 
 [A cylindrical tin vessel 
 A (a biscuit tin will do), 
 about 10 cm. in height and 
 6 cm. in diameter, has four 
 smooth holes bored at equal 
 distances from each other, 
 to which corks are fitted 
 water-tight. Through each 
 cork passes a thermometer. 
 The cover B of the vessel 
 is turned over and rests on 
 the top, serving to contain 
 the freezing mixture.] 
 
 Apparatus (Fig. 8). 
 
 Ice : Salt : Curve-paper. 
 
 Experiment. Fill the vessel A quite full with distilled water 
 
 and place as much of a freezing mixture of crushed ice and salt 
 
 Fig. 8. 
 
B. Expansions. 37 
 
 {i part of salt to 2 parts of ice] as possible into the cover B. 
 Replace <be cover so that the bottom of it is in contact with the 
 surface of the water-w-i. Mark the temperatures indicated by 
 the four thermometers every mimte^uid arrange your results in 
 a tabular form. No i will cool rapidly at first bliiue 4he water 
 on cooling becomes denser and sinks to the bottom. No. 2 
 will cool more slowly, and No. 3 and 4 still more slowly until 
 the lowest thermometer reaches the temperature of maximum 
 density of water (about 4°). This one remains stationary while 
 No. 2, 3, and 4 will in order arrive at this temperature. After 
 this the water on furthe^ cooling expands, and being less dense 
 No. 4, which was the last to reach 4°, will be the first to cool 
 to 0°. The other thermometers, No. 3, 2, i, will successively 
 attain 0°. Plot on the same piece of curve-paper your results 
 for the four thermometers, taking the times as abscissae and 
 the corresponding temperatures for the ordinates. It will be 
 found that the curves will cross each other along a horizontal 
 line, which, on being continued, cuts the temperature axis at 
 the temperature of the maximum density of water. It is im- 
 portant that the observer should not come closer to the 
 apparatus than is absolutely necessary to read the thermometers 
 as the radiation from the body will prevent the water cooling 
 sufficiently. 
 
 26. Determination of the expansion of air at constant 
 pressure (Method 1) '". 
 
 Apparatus. A piece of thermometer tubing about 15 cm. 
 long : Beaker : Thermometer : Sand-bath : Bunsen Burner : 
 Mercury : Curve-paper. 
 
 Experiment. Dry the thermometer tubing thoroughly : close 
 one end of it in the flame. Dip the open end under the surface 
 of clean mercury and heat it strongly with the Bunsen to drive 
 out a portion of the air. On allowing it to cool, a thread of 
 mercury will be forced up the tube, enclosing a certain volume 
 
 * In this and the two following experiments we neglect the expansion of 
 the glass. 
 
a8 
 
 Practical Work in Heat. 
 
 of air. Tie this tube to a thermometer, placing the closed end 
 opposite the zero. Support them vertically in a beaker of water 
 on a sand-bath so that the whole column of air is under the 
 surface. Read the temperature, i, of the water and the volume, 
 V, of the enclosed air in terms of the thermometer divisions. 
 Heat the water gradually, keeping it well stirred. At about 
 every io° rise of temperature read the thermometer and the 
 volume of the enclosed air ^^. Continue this until the water boils 
 and enter your results in a tabular form. 
 
 Temperature. 
 
 Volume of air. 
 
 Mean coefficient of 
 expansion of air. 
 
 Expansion 
 of I c.c. 
 
 t 
 
 ■B 
 »2 
 
 »2 
 
 I 
 
 To get the numbers in the third column let us find o,. 
 
 A volume v^ c.c. expands by v^—v.^ c.c. for a rise of tem- 
 perature (/j— /i)°; 
 
 I c.c. expands by 
 
 —-. c.c. for i°C, which gives us a^, 
 
 the mean coefficient of expansion of air between these tempera- 
 tures. To get the numbers in the fourth column divide those in 
 the second column by v. 
 
 Plot your results on a curve, taking the temperatures as the 
 abscissae and the corresponding numbers in the fourth column 
 as the ordinates. What does the form of the curve show? 
 Compare it with the curve obtained in Experiment i8. 
 
 26. Detennination of the expansion of air at constant 
 pressure (Method 2). 
 
 Apparatus. A round bottomed flask fitted air tight with a 
 one-holed bung. Through the hole passes a piece of glass 
 
 "' See Note 17. 
 
B. Expansions. 29 
 
 tutnng to which is attached a short piece of india-rabber tubing. 
 A vessel [in which to place the flask] containing a little water : 
 Beaker : Thermometer : Litre measuring jar : Clip : Bunsen 
 Burner. 
 
 Experiment. Thoroughly dry the flask, and after fitting the 
 bung tightly into the neck support it inside the vessel so that it 
 is just above the surface of the water. Cover with a piece of 
 cardboard through a hole in which the neck of the flask passes. 
 Boil the water briskly for about 5 or 10 minutes, and, after 
 reading the barometer, find the temperature, T, of boiling 
 water. We now have tlTe flask full of air at 7*. Clip the india- 
 rubber tubing and take the flask out of the vessel and let it cool. 
 Then invert it so that its nedk dips under cold water, and open 
 the clip. The water will rise in consequence of the contraction 
 of the air. Shake the water up with the air for at least five 
 minutes, keeping the neck of the flask under water. Then clip 
 the india-rubber tubing and measure the volume, v, of the water 
 that has entered and note its temperature, /. Then fill the flask 
 with water up to the point where the india-rubber tubing was 
 clipped in the first instance and measure its total volume, V. 
 
 It is evident that a volume V—v c.c. of air would on expanding 
 by V C.C. fill the flask at T°. 
 
 .: V—v C.c. expand by v c.c. for a rise of temperature 
 
 {T-t)° \f suppose], 
 
 V 
 
 .•. I c.c. expands by '. r— c.c. for i°C, 
 
 "^ ' {V—v)t 
 
 which is the mean coefiicient of expansion of air between these 
 temperatures. 
 
 27. Determination of the coefflcient of increase of 
 
 pressure of air at constant volume. 
 
 [A glass tnbe with a bulb B about 5 cm. in diameter, blown at one end, 
 is bent twice at right angles as in the figure, the longer limb being A:om 
 40 to 45 cm. in length. All moisture must be carefully expelled from it 
 by warming the bulb over a flame. The end of the tube is joined by a 
 piece of india-rubber tubing '" about 50 cm. long to another similar piece 
 
 " Thick india-rubber tubing lined with canvas ought to b: used to 
 withstand the pressure. 
 
3° 
 
 Practical Work in Heat. 
 
 of glass tubing A about a metre in length. Fill the longer limb of B, the 
 india-rubber tubing and part of the tube A with clean dry mercury. A 
 
 small piece of paper is gummed on 
 at 'a' to serve as a mark. This 
 apparatus should be attached by 
 pieces of leather to a wooden sup- 
 port. Instead of using the india- 
 rubber tubing a more convenient 
 method is to join the ends of the 
 two tubes by two branches of a 
 thick india-rubber T-tube, the third 
 branch being firmly bound to the 
 nozzle of an ordinary india-rubber 
 air ball. Pressure is exerted on the 
 mercury filling the ball by a screw 
 passing through a piece of wood 
 resting on the ball, the opposite 
 edge of the piece of wood being 
 hinged to the base-board. 
 
 Apparatus (Fig. 9). Beaker : 
 Thermometer: Metre rule: 
 Bunsen Burner : Curve-paper. 
 Experiment. Bring a beaker 
 of water up so as to completely 
 immerse the bulk B and as 
 much of the tube as possible. 
 Raise or lower A^^ so as to 
 bring the level of the mercury exactly to the mark a. Note 
 the temperature, /, of the water and the diiference of level, 
 h, if any, of the mercury in the two tubes. Read the baro- 
 metric height, ff. The enclosed air is now at temperature / 
 and under a pressure H+h, according as the mercury in A 
 is higher or lower than that in the other limb. Heat the 
 water in the beaker, keeping it continually stirred, till the 
 temperature rises about 10°. The air will expand and press 
 down the mercury below a. In order to reduce the air to the 
 same volume as before, raise the tube A "' until the level of the 
 mercury returns to a. Note the temperature, t^, and the differ- 
 
 *■ Or if the india-rubber ball replaces the tubing alter the levels by the 
 screw. 
 
B. Expansions. 
 
 31 
 
 ence, A,, of the heights of the mercury columns, being sure that 
 the air and the water are at the same temperature". Take 
 similar readings at about every 10° rise in temperature until 
 the water boils, and enter your results in a tabular form as 
 follows : — 
 
 Temperatures. 
 
 Difference in heights 
 of mercury columns. 
 
 Pressure of 
 enclosed air. 
 
 Mean coefficient of 
 increase of pressure. 
 
 i 
 
 h 
 
 H+hi = P, 
 
 •*2 
 
 Barometric height, H = ... mm. 
 
 To get the numbers in the fourth column, let us find Oj. 
 The pressure P^ increases to P^ for a rise of temperature /j— /„ 
 .". unit pressure increases by 
 
 which is the mean coefficient of increase of pressure between 
 these temperatures. 
 
 Plot your results in a curve taking the temperatures as 
 abscissae and the corresponding pressures in the third column 
 as ordinates, and compare with the curve in Experiment 25. 
 
 We have assumed that the small volume of air in the short 
 branch tube between the level of the water in the beaker and 
 the mark a is at the same temperature as the air in bulb. 
 For greater accuracy we should have to allow for this not 
 being so. 
 
 N. B. When you have finished be careful to lower A as far as 
 it will go, as otherwise, when the air cools, mercury will be 
 forced into the bulb. 
 
 " See Note 17. 
 
33 Practical Work in Heat. 
 
 C. Calorimetry, 
 
 The unit of heat, called a calorie, is that quantity of heat 
 which is required to raise i gram of water one degree centi- 
 grade. We shall assume that this is constant all through the 
 scale of temperatures. 
 
 The specific heat of a substance is the quantity of heat required 
 to raise i gram of the substance i°C, or the quantity emitted by 
 I gram when cooling i°C. 
 
 The heat of fusion is the quantity of heat required to 
 transform i gram of a solid to the liquid state at the melting 
 point or vice versd. The .heat of vaporisation is the quantity 
 of heat required to transform i gram of a liquid to vapour 
 at the boiling point or vice versd under given atmospheric 
 pressure. 
 
 N. B. In the following experiments on the measurements of 
 quantities of heat, we must arrange to lessen as much as possible 
 conduction and radiation of heat from the calorimeter. To 
 prevent conduction the calorimeter may either be supported on 
 a triangle of cord tied to a ring of the retort-stand, or may be 
 packed in an empty beaker with cotton wool, or better still, be 
 supported by strings inside a tin vessel. 
 
 The methods by which the errors due to radiation are 
 corrected are beyond the scope of this book, and therefore we 
 must try and lessen the amount of radiation. This may be 
 done by polishing the outside of the calorimeter and the inside 
 of the tin vessel in which it is placed, and also by placing so much 
 liquid in the calorimeter that the final temperature may not 
 be much above the temperature of the room. We shall assume 
 that the above precautions are taken in each of the following 
 experiments in Calorimetry. When two thermometers are used 
 they must always be compared first, either as in Experiment 3 or 
 by dipping them into the same beaker of water, and the reading 
 taken on one must be reduced to what it would be on the 
 other. 
 
C. Calorimetry. 33 
 
 28. Determination of the water value of the Calori- 
 meter and Thermometer. 
 
 Apparatus. A metal vessel to be used as a Calorimeter : 
 Beaker : Two Thermometers : Sand-bath : Bunsen Burner. 
 
 Experiment. Counterpoise the calorimeter, and support a 
 thermometer with its bulb inside the vessel. Heat some water 
 in a beaker to about 25° or 30°C, and take its temperature, T, 
 with the other thermometer. Let the temperature of the calori- 
 meter be t°. Quickly pour some of the warm water into the 
 calorimeter so that it is about half full. Stir well and read the 
 highest temperature, Q, tft which the thermometer rises before it 
 begins to cool again. Weigh and find the mass, m, of water 
 that has been poured in. 
 
 m grams of water have cooled from r° to 0°, therefore they 
 have given out m^T—d) calories. These have been absorbed 
 by the calorimeter and thermometer, raising their temperature 
 
 from t° to 6°, .•. — 3 — — -^ calories would raise them i°C. 
 
 This quantity is called their 'water value' or 'heat capacity'. 
 It is evidently equal to the number of grams of water that 
 would have been raised the same number of degrees. 
 
 Repeat this experiment, using water that has been heated to 
 70°, and enter your results in a tabular form '". 
 
 29. Determination of the specific heat of a solid by 
 the method of mixtures (Method 1). 
 
 Apparatus. Calorimeter "" : Two Thermometers : Beaker : 
 Test-tube : Bunsen Burner : Leaden Shot. 
 
 Experiment. Fill the test-tube half full of shot and put the 
 bulb of the thermometer in the middle of it. Put the test- 
 tube in a beaker of water and heat to boiling. Counterpoise 
 the calorimeter, fill it two-thirds full of water, and find the mass, 
 m, of water it contains. Note its temperature, /. When the 
 thermometer in the test tube has become quite stationary read the 
 
 '"' In determining specific heats and heats of fusion the first value of the 
 water value is to be used : for the heats of vaporisation the second value. 
 
 " In the following experiments the water value of the calorimeter and 
 thermometer is denoted by )i. See Note 25. 
 
34 
 
 Practical Work in Heat, 
 
 temperature, T, of the shot. Take out the thermometer and 
 quickly transfer the shot to the calorimeter. Stir continually, and 
 note the highest temperature, fl, indicated 
 by the thermometer before it begins to 
 cool. Weigh the calorimeter and de- 
 termine the mass, M, of shot intro- 
 duced. 
 
 The heat received by the calorimeter 
 and water on being heated from /° to fl° is 
 (m + ii){Q—t), which is equal to the heat 
 given out by the mass M of Lead on cool- 
 ing from 7* to fl°, 
 
 .-. mass M of Lead on cooling {T—d)° 
 gives out (m + fj) {6—t) calories ; 
 
 (m + ix)(e-t) 
 
 Fig. lo. 
 
 .-. I gram of Lead on cooling i° gives out 
 which is the required specific heat. 
 
 M(T-e) 
 
 In the case of solids acted on by water we must put in the 
 calorimeter a liquid (whose specific heat, s, we know) that does 
 not act on the solid. The specific heat of the solid is in this case 
 
 M{r—e) 
 
 Determine as above the specific heats " of Copper, Iron, Zinc, 
 Crystallised Copper Sulphate [in a concentrated solution of 
 the same whose specific heat must be determined as in Experi- 
 ment 34]. 
 
 [Instead of heating the solid in a test-tube in a beaker of water, a better 
 plan would be to use the apparatus of Fig. 10. ^ is a glass tube 9 cm. long 
 and 1-5 cm. in diameter, closed at one end by a cork, through which passes^ 
 a thermometer T. This tube passes through two corks closing the ends 
 of a wider glass tube.<4, 10 cm. long and 4 cm. in diameter. Two elbow- 
 tubes pass through the corks of A, the upper one C being connected with 
 a boiling can, the lower one D allowing the steam to escape. The solid 
 is hung by a thread close to ,the bulb of the thermometer. Steam is passed 
 through the outer cylinder till the thermometer rises no more. By raising 
 the cork we allow the solid to drop into the calorimeter placed under the 
 tube £.} 
 
 " The solid must either be in small pieces, in powder, or in sheets 
 
C. Calorimetry. 35 
 
 30. Determination of the specific heat of a solid by 
 the method of mixtures (Method 2). 
 
 Apparatus. Calorimeter : Beaker : Two Thermometers : 
 Wire cage : Bunsen Burner : Beeswax. 
 
 Experiment. In the case of a solid lighter than water, or of 
 one that sticks to the test-tube on being heated, we must first 
 find its mass, M; then place it in a small open wire cage whose 
 mass, m', and specific heat, s, we know, and hang it by a thread 
 in water which we raise to a temperature, T, below the known 
 melting point of the solid. Counterpoise the calorimeter and 
 fill it two-thirds full of water. Find the mass, m, of water intro- 
 duced and determine its temperature, t. Quickly transfer the cage 
 to the calorimeter, note, the final temperature, Q, and weigh ag^in 
 to determine the mass, m", of water that was carried over. Then 
 since the heat given out by the solid, the cage, and water, m",, 
 is equal, to the heat received by calorimeter, thermometer and 
 water, m, we have, if x is specific heat of the solid, 
 
 \Mx-\-m's-\-m"\ {T—ff) = (m + fji) {O—t); 
 hence we determine x. 
 
 Determine as above the specific heat of Paraffin-wax. 
 
 SI. Determination of the specific heat of a solid by 
 fusion of ice. 
 
 Apparatus. Beaker : Test-tube : Thermometer : Bunsen 
 Burner : Cotton wool : Small block of Ice : Small piece of Lead. 
 
 Experiment. Weigh the piece of lead, M, and put it and 
 a thermometer in a test-tube immersed in a beaker of water. 
 Heat the water to boiling. Counterpoise a small piece of cotton 
 wool attached to a piece of glass tube as a handle. Bore out 
 a hole in the block of ice and carefully dry it. When the 
 thermometer in the test-tube has become quite stationary read 
 the temperature, T, and quickly transfer the lead to the hole in 
 the ice. Let it remain till it has cooled to 0°. Then sop up 
 with the cotton wool the water that is formed. Weigh the 
 cotton wool and determine the mass, m, of the ice , that has 
 melted. One gram of ice requires 79-25 calories to melt it, 
 
 D 2 
 
3<S Practical Work in Heat. 
 
 therefore 79-25 m calories have been given out by M grams of 
 lead in cooling from r" to 0°, therefore i gram of lead would 
 
 give out — calories on cooling 1°, which is the required 
 
 specific heat. 
 
 Determine as above the specific heats of Copper and Iron, 
 and compare your results with those obtained in Experiment 29. 
 
 32. Determination of the specific heat of a liquid by 
 the method of mixtures (Method 1). 
 
 Apparatus. Calorimeter : Beaker : Thermometer : Bunsen 
 Burner: Turpentine. 
 
 Experiment. Counterpoise the calorimeter and pour in 
 enough turpentine to fill it rather more than half full. Find the 
 mass, M, of the turpentine. Boil some water in a beaker "' and 
 find from the tables the boiling point, T, under the existing 
 atmospheric pressure. Place a thermometer in the calorimeter 
 and note the temperature, /, of the turpentine. Quickly pour 
 some of the boiling water into the calorimeter and, stirring the 
 mixture together, note the highest temperature, 6, to which 
 the thermometer rises. Weight the calorimeter and determine the 
 mass of water, m, introduced. 
 
 Now m grams of water have cooled from T° to 6P, and have 
 given out m{T—d) calories, which have heated the calorimeter 
 and the turpentine from /° to d^. The calorimeter has taken 
 fi{d — t) calories. 
 
 .-. m{T—d)—iJ.{6—t) calories have heated M grams of 
 Turpentine (fl-/)°; 
 
 m{T-e)-ix(0-t) , . ,^ . 
 
 .•. MlH—h calories would raise i gram of 
 
 Turpentine 1°, which is the required specific heat. 
 
 Determine as above the specific heat of Mercury, and of a 15 
 per cent, solution of Ammonium Chloride, and a 20 per cent, of 
 solution of Sodium Chloride. 
 
 '" The beaker ought to be nearly full of water, so that but little heat is 
 lofst on pouring it into the calorimeter. 
 
C. Calorimetry. 37 
 
 38. Determination of the apeciflc heat of a liqiiid by 
 the method of mixtures (Method 2). 
 
 Apparatus. Same as for Experiment 32, and, in addition, 
 Alcohol. 
 
 Experiment. In the case of a liquid which emits or absorbs 
 heat on being mixed with water we cannot determine its 
 specific- heat as above, but instead of water must use some 
 liquid, whose specific heat, s, is known, which has no action on 
 the given liquid. For instance, to find the specific heat of 
 alcohol, we may raise it to its known boiling point T, and pour 
 it into a mass, m, of turpentine in the calorimeter at tempera- 
 ture, /. As above we determine the final temperature, 0, and mass 
 of alcohol, M, introduced. The heat given out by the alcohol on 
 cooling from t" to Q° is equal to the heat absorbed by the calori- 
 meter and turpentine on being heated from t° to 6°. Therefore, 
 
 MX {T—6) = {ms + /x) {d—t), 
 whence x, the required specific heat of alcohol, can be determined. 
 
 Determine as above the specific heat of concentrated sulphuric 
 acid. 
 
 34. Determination of the specific heat of a liquid by 
 the method of mixtures (Method 3). 
 
 Apparatus. Calorimeter : Beaker : Two Thermometers : 
 Bunsen Burner : Turpentine : Leaden Shot. 
 
 Experiment. Instead of using a second liquid as in Experi- 
 ments 32 and 33 we may use a solid, such as Lead, whose 
 specific heat, s, is known. Having as in Experiment 32 poured 
 into the calorimeter a known mass, M, of Turpentine whose 
 temperature, /, we determine, put some of the shot into a test- 
 tube with a thermometer and place it in a beaker of water 
 which we heat to boiling. When the thermometer stops rising 
 read tlje temperature, T, of the lead and quickly transfer it to 
 the calorimeter and, stirring, note the final temperature, 6. 
 Weigh the calorimeter and find the mass, m, of shot introduced. 
 The lead on cooling from r° to &° gives out ms {T-d) calories 
 of which jJL (O—t) have gone to heat the calorimeter, therefore 
 
38 Practical Work in Heat. 
 
 ms{T—$)—n{d—/) have heated M grams of Turpentine from 
 
 ^°to0°; 
 
 therefore ^.(r-g)-^(e-/) 
 
 M{d-i) 
 calories would heat i gram of Turpentine 1°, which is the 
 required specific heat. 
 
 Determine as above the specific heats of Glycerine, of Alcohol, 
 and of concentrated Sulphuric Acid. 
 
 35. Seterminatioii of the specific heat of a liquid by 
 the method of cooling *'. 
 
 Apparatus. Calorimeter '" : Beaker : Thermometer : Bunsen 
 Burner : Mercury. 
 
 Experiment. Counterpoise the calorimeter. Heat some clean 
 dry mercury up to about 70° or 80°, and pour some of it 
 into the calorimeter so as to fill it about half full. Put the 
 thermometer in the mercury " and observe the time it takes to 
 cool every 5° down to 40°. Weigh calorimeter and find mass, 
 M, of mercury in it. Empty the mercury out and repeat exactly 
 the same series of observations with water instead ; being careful 
 to fill the calorimeter with the water to the same height as the 
 mercury was at. Let m be the mass of water introduced. 
 
 To determine the specific heat from our observations we 
 must remember that Dulong and Petit proved by experiment 
 that when two different liquids are allowed to cool in an enclo- 
 sure of a constant temperature, the velocity with which either 
 cools only depends on the excess of its temperature over that of 
 the enclosure and on the nature and extent of the surface at which 
 the cooling takes place, and is independent of the nature of 
 the liquid. Therefore, since we fill the same calorimeter to the 
 same height in both cases, the amount of heat given out per 
 minute by the mercury and the water must be the same 
 between the same range of temperatures. If M is the mass of 
 
 " This method gives satisfactory results only with liquids which are good 
 conductors of heat. 
 
 '" When mercury is used the calorimeter must not be of tin. In this case a 
 glass beaker may do. We must determine its water value as before 
 
 " See Note 6. 
 
C. Calorimetiy. 
 
 39 
 
 mercury and if it takes «, minutes to cool 5°, the heat given out 
 per minute is 
 ^(Mx + n) 
 
 «i 
 
 -J where x is the specific heat of mercury. 
 
 The heat lost per minute by a mass m of water which takes »,' 
 minutes to cool through the same 5° is 
 
 Equating the above two expressions we determine x, the 
 required specific heat. 
 
 Enter your results in*a tabular form as follows : — 
 
 Temperature. 
 
 Time of cooling. 
 
 Specific heat 
 of mercury. 
 
 Mercury. 
 
 Water. 
 
 7o°-65"' 
 
 
 »2 
 
 ^1 
 
 Mean = 
 
 Mass of water, m = . . . grs. 
 Mass of mercury, M=... grs. 
 
 Determine as above the specific heat of Glycerine. 
 
 36. Determination of the amount of heat absorbed or 
 emitted on forming a solution. 
 
 Apparatus. Calorimeter: Beaker: Thermometer: Powdered 
 Ammonium Chloride. 
 
 Experiment. Counterpoise the calorimeter and pour into it 
 100 grams of water whose temperature, /, we note. Weigh 
 about 15 grams of Ammonium Chloride and transfer it to the 
 calorimeter. Keep stirring the mixture and read the lowest 
 temperature, Q, to which the thermometer sinks. Then weigh 
 the calorimeter and determine the exact mass, m, of the salt 
 introduced. 
 
 The amount of heat absorbed cooled the solution, whose 
 known specific heat is s, and the calorimeter from /° to fl°, 
 
40 Practical Work in Heat. 
 
 therefore the heat absorbed by dissolving i gram of Ammonium 
 Chloride in loo grams of water is 
 
 \{ioo + m)s+y^{t-e) ^ 
 m 
 which is called the ' Heat of Solution ' of the solid. 
 
 Determine as above the heat of solution of Sodium Chloride. 
 
 N.B. Specific heat of a 15 per cent, solution of Ammonium 
 Chloride is -89. 
 
 Specific heat of a 20 per cent, solution of Sodium Chloride 
 is -86. 
 
 In both cases the alteration per cent, of the specific heat may 
 be taken as -005. 
 
 37. Determination of the Heat of Fusion of Ice. 
 
 Apparatus. Calorimeter : Beaker : Thermometer : Ice. 
 
 Experiment. Counterpoise the calorimeter and fill it three 
 parts full of water whose mass, m, we determine. Support a 
 thermometer in it and note its temperature, /. Clean a piece 
 of ice and break it up into small pieces and transfer them one 
 by one to the calorimeter, after brushing oiF the moisture from 
 them, by a pair of crucible tongs whose points are wrapped in 
 flannel. Be careful not to put so much ice in that it cannot 
 all be melted. For 50 grams of water at 15°, 4 cub. cm. of 
 ice will be sufficient. Keep stirring the ice with the water 
 until it is all melted, and note the lowest temperature, Q, to 
 which the thermometer sinks. Weigh the calorimeter and 
 determine the mass, M, of ice introduced. The water and 
 calorimeter have been cooled from t Xa Q\ the amount of heat 
 given out by them is therefore 
 
 (m^lK){t-e). 
 Part of this has gone to melt the ice and part to raise the 
 resulting water from o to 6. The latter quantity is MQ, there- 
 fore the amount gone to melt the ice is 
 
 {mJriC)(t-ff)~MQ, 
 
 ,, , c • ■ {m + u){t—6)—Md 
 therefore i gram of ice requires ^^ !-^-^ '- to melt 
 
 to I gram of water at 0°, which is the required heat of fusion. 
 
C. Calorimetry. 41 
 
 38. Determination of the heat of Fusion of a solid 
 
 (Method 1). • 
 
 Apparatus. Calorimeter : Beaker : Two Thermometers : 
 Bunsen Burner : Paraffin-wax. 
 
 Experiment. Counterpoise the calorimeter. Place in it 
 about 5 grams of paraffin-wax whose specific heat, s, is known, 
 and find its mass, M: heat some water in a beaker up to 
 about 70°. Place a thermometer in the calorimeter and deter- 
 mine its temperature, t. Read the temperature'* of the hot 
 water, T, and pour enougli of it into the calorimeter to fill it two- 
 thirds full ; keeping it stirred, read the temperature, 0, to which 
 the thermometer sinks before it begins to cool slowly by 
 radiation. Now weigh the calorimeter and find the mass, mi 
 of water that has been poured in. The hot water has given 
 out m(^T~Q) calories, of which {Ms + ii) (0—t) have been 
 absorbed by calorimeter and wax in being heated from t° to 6°. 
 
 .: m{r—d)—{Ms+fJi.){d—i) have been used to melt the 
 
 .,, r c ■ m{T-d)-{Ms + ij){e-t) 
 wax, therefore i gram of wax requires — ^ — ^ -^ ■ 
 
 to melt it, which is the required heat of fusion. 
 
 N.B. — In this experiment we assume that the specific heat of 
 wax in the solid and the liquid state is the same. This assump- 
 tion is not a legitimate one, and in the following experiment the 
 error thus introduced is eliminated. 
 
 *ZQ. Determination of the heat of Fusion of a solid 
 
 (Method a). 
 
 Apparatus, Same as in Experiment 38. 
 
 Experiment. If the specific heat of the substance in the 
 liquid state is not known, we can, by performing two experi- 
 ments similar to Experiment 38, in which the masses of the 
 wax and the water, as well as the original temperature of the 
 water are different, determine not only the latent heat but also 
 the specific heat of the substance in the liquid" state. 
 
 " The temperatnre must be such that the 6nal temperature is above the 
 melting point of the solid. 
 
42 
 
 Practical Work in Heat. 
 
 Suppose (^ is the melting point of the solid, 
 
 s the specific heat of the substance in the solid state, 
 / the specific heat of the substance in the liquid state; 
 and X the heat of fusion of the solid. 
 If in the first experiment we take m grams of water at 7* 
 and M grams of the solid at t°, and find the resulting tempera- 
 ture 6, then since the heat given out by the water is equal to 
 the heat which raises the calorimeter and solid from /° to the 
 meking point, and melts the solid at this temperature and 
 then raises the liquid and the calorimeter to 6°, we have 
 
 {MsJt^i){^-l)-^Mx + {Ms' + ii){e-<it)-m{T-6). (i) 
 By taking in a second experiment M' grams of the solid and 
 m' grams of hot water at 7^°, supposing 6'" to be the resulting 
 temperature, we have 
 
 (M's + ii){^-t) + M'x + (M's'+]j) {6'-^) = m'(r'-6'). (2) 
 The only two unknowns are x and s', which we can find by 
 solving the two simultaneous equations. 
 
 Determine as above the heat of fusion of Beeswax. 
 
 40. Determination of the heat of vaporisation of Water. 
 
 [^ is a flask about 300 cubic cm. 
 capacity, through the cork of which 
 pass a thistle funnel and one end of a 
 tube B bent twice at right angles, as in 
 the flgure. The other end of B fits 
 into a hole of a cork closing one end of 
 a piece of wide glass-tubing A, 8 to 
 10 cm. in length and 2.5 cm. in diameter. 
 The other end of A is also tightly closed 
 with a cork, through which passes a 
 piece of glass-tubing C, the upper end 
 of which is above the level of the end 
 of the tube B, and its lower end is con- 
 nected by a piece of india-rubber tubing 
 to another short piece of glass tubing.] 
 
 Apparatus (Fig. 11). Calori- 
 meter : Thermometer : Bunsen 
 Burner. 
 Experiment. Fill the flask half full of water, and heat to 
 boiling. Counterpoise a calorimeter and fill it two-thirds full 
 
 Fig. II. 
 
C. Calorimetty. 43 
 
 of water. Weigh to determine mass, m, of water. When the 
 steam has been coming off freely from the delivery tube, note 
 the temperature, /, of the water in the calorimeter and let the 
 delivery tube dip under its surface. Allow the steam to pass 
 into the water, keeping it well stirred until the temperature has 
 risen about 70°. Pinch the india-rubber connecting tube and 
 take the delivery tube out of the water and note the final tempera- 
 ture, 6, to which the thermometer rises. Weigh the calorimeter 
 and determine the mass, M, of steam condensed. Note baro- 
 metric height and determine the temperature, T, of the boiling 
 water. The calorimeter aUd the cold water have risen from f to 0°, 
 therefore have absorbed {m + fi) (6—i) calories". The con- 
 densed steam has cooled from 7"° to fl°, giving out M{T—G) 
 calories, therefore the amount of heat given out by M grams of 
 steam condensing to water at 7"° is (w«-H*) {d—t)—M{T—ff). 
 The amount that one gram of steam gives out on condensing to 
 water at T° is therefore 
 
 {m + ]i){6—t)—M{T-ff) 
 
 H ' 
 
 which is the required heat of vaporisation of water. 
 
 41. Determination of the heat of vaporisation of alcohol. 
 
 Apparatus. Same as in Experiment 40 with addition of 
 Alcohol. 
 
 Experiment. As alcohol mixed with water emits heat we 
 must pass the vapour into alcohol instead of into water. Fill 
 the flask half full of alcohol and raise it to its known boiling 
 point T. Fill the calorimeter half full of alcohol and determine 
 the mass, M, introduced, and also its temperature, /. Proceed- 
 ing in a similar way as in Experiment 40 we pass the vapour 
 into the alcohol and note the final temperature, fl, and deter- 
 mine the mass, M, of alcohol vapour condensed. Then, if s is 
 the known specific heat of alcohol and x is latent heat, we have 
 
 MxJfMs (r—e)={ms + n) (6—t), 
 whence we can determine x, the heat of vaporisation required. 
 Determine as above the heat of vaporisation of Turpentine. 
 
 " See Note 25. 
 
44 
 
 Practical Work in Heat. 
 
 Fig. 12. 
 
 D. Evaporation. 
 *42. Determination of the vapour tension of Alcohol. 
 
 [A, a flask of about 300 c.c. capacity with 
 rather a wide neck, is fitted with an air-tight 
 cork. Through this passes one end of a 
 U-tnbe C about -5 cm. in diameter, bent as in 
 the figure, the longer limb of which is about 
 30 cm., the shorter about i.i; cm. in length. 
 Through the cork also passes a piece of wide 
 glass-tubing B about 6 cm. in length and 75 
 cm. in diameter, the ends of which are closed 
 by smooth plugs of cork '*.] 
 
 Apparatus (Fig. 1 2). Beaker : Ther- 
 mometer : Metre Scale : Bunsen 
 Burner : Alcohol : Curve-paper. 
 
 Experiment. Pour into the tube C 
 sufficient clean mercury to fill it 
 nearly to the level of the horizontal branch. Fit it to the 
 cork, and fit the cork tightly into the flask. Place the flask 
 in a beaker of water on a sand-bath and note the temperature, /j. 
 Read off the difference of levels, if any, h, of the mercury, and 
 note the barometric pressure, H. The pressure of the air in the 
 flask is H+h, according as the level in the shorter arm is below 
 or above that in the longer arm. Let this pressure be P^. The 
 next step will be to introduce some alcohol into the flask without 
 opening ,any communication with the external air. To do this take 
 out the upper plug from the tube B and nearly fill the latter with 
 alcohol. Replace the plug and push it down the tube. As the 
 alcohol is compressed it will force out the lower plug and drop 
 into the flask and will saturate the space with its vapour. Read 
 off the difference of levels of the mercury h^ Then H+h^ gives 
 us the pressure of the alcohol vapour and air at t^. Therefore 
 A,— A is the pressure, /, due to the alcohol alone. Heat the water 
 
 " The plugs cut out by the usual cork-borers in making holes through 
 a cork will do very well, if smoothly cut. 
 
D. Evaporation. 
 
 45 
 
 gradually, keeping it well stirred until the thermometer rises 
 about 5°. Read the temperature, /j, and the difference of levels, 
 A, '"'. Then 11+ h^ gives the pressure of the alcohol-vapour and 
 air. Continue heating and reading the thermometer and differ- 
 ence of levels for every 5° rise of temperature until the ther- 
 mometer marks 50°. Enter your results in a tabular form as 
 
 follows : — 
 
 Barometric height, ^=...inm. 
 
 Temperature. 
 
 Difference 
 of levels. 
 
 Pressure of 
 alcohol ■(■ air. 
 
 Pressure of air. 
 
 Pressure of 
 alcohol. 
 
 
 
 
 ^1 
 
 A 
 
 To get the pressure due to the alcohol alone we must subtract 
 from the numbers in the third column the corresponding 
 pressures due to the air, entered in the fourth column. To get 
 them, let us find />,. For every degree rise in temperature the 
 pressure of the air increases by ^^rd of its original pressure "", 
 i. e. by '00366 P^ On the temperature rising from /°i to /°, the 
 pressure P^ becomes P-^^ [i -1- -00366 (/, — /J], which is P^. 
 
 Plot a curve, taking the temperatures as abscissae, and the 
 corresponding vapour-pressures of alcohol as ordinates. 
 
 Determine as above the vapour-pressure of Turpentine. 
 
 43. Determination of the pressure of aqueous vapour 
 
 at temperatures below 100°. 
 
 [Take a thick glass tube A closed at one end about 50 cm. in length and 
 '75 cm. in diameter. To the other end attach a piece of thick india-rubber 
 tubing " R about 50 cm. long, and fill both glass and rubber-tubing with 
 clean dry mercury up to within about 2 cm. of the open end. Fill the 
 empty part with distilled water. Pinch the india-rubber tube, and raise the 
 glass tube so that the water passes to the closed end, being careful that no 
 
 " See Note 17. 
 
 " For the small range of temperatures we can use this approximation 
 instead of the true increase, viz. ■^■^ri of its original pressure at 0°. 
 
 " Thiclc india-rubber tubing lined with canvas ought to be used, to with- 
 stand the pressure. 
 
46 
 
 Practical Work in Heat. 
 
 air-bubbles pass up as well. Fit on another tube B about a metre in 
 length to the india-rubber tubing and pour in a little more mercury. Pass 
 the closed end of A through a cork fitting tightly into the neck of a 
 deflagrating jar about 9 cm. in diameter at the broad end (Appendix B. 6). 
 Make a mark at 'a' about 2.5 cm. from the closed end of A. This 
 apparatus should be attached to a wooden support by leather bands. 
 It would be more convenient to replace the india-rubber tubing by a 
 T-tube and india-rubber ball as described under Fig. 9.] 
 
 Apparatus {Fig. I ■i). Thermometer: 
 Boiling Can : Metre Rule : Bunsen 
 Burner : Curve-paper. 
 
 Experiment. Nearly fill the jar C 
 with water and place a delivery tube in 
 it so that it reaches nearly to the bottom. 
 Connect this tube with the boiling can 
 so that steam may be passed into the 
 water contained in C. Place a thermo- 
 meter in C with its bulb near the closed 
 end of the tube A. Raise or lower the 
 tube B '* so that the level of the mercury 
 may reach the mark a. Read the tem- 
 perature of the water /j and also the 
 difference of levels of the mercury in the 
 two tubes Aj. Note the barometric pres- 
 sure H. The pressure of the vapour of 
 the water in the closed tube is therefore 
 H—h^ Pass steam into the jar C until 
 the temperature rises about 5°. The 
 pressure of the water-vapour increases 
 and . will push the mercury below a. 
 Bring the level of the mercury back to a 
 by raising the tube B, Take the de- 
 livery tube out of C and stir the water, 
 and read the temperature, /j, when it has become stationary. 
 Readjust the level of the mercury to the mark a and read the 
 difference of levels h^. Repeat this, raising the temperature 
 
 ^" If we replace the india-rubber tube by the india-rubber ball we must 
 alter height by pressure on it. 
 
 Fig- 13- 
 
D. Evaporation. 
 
 47 
 
 each time about 5° until the water boils, and enter your results 
 in a tabular form as follows : — 
 
 Temperatures. 
 
 Difference of levels. 
 
 Pressure of vapour. 
 
 '. 
 k 
 
 \ 
 
 H-hy 
 
 Barometric height, H = .. .mm. 
 
 • 
 
 Plot your results in a curve, taking the temperatures as abscissae 
 and the corresponding pressures as ordinates. 
 
 N.B. To obtain a more accurate result we ought to allow for 
 
 the fact that the upper portion of the mercury column QiA which 
 
 is immersed in the water is at a higher temperature than the rest 
 
 of the mercury. Suppose at any given excess of temperature t 
 
 the difference of levels. between A and B is h, of which the length 
 
 U is outside and h" in the water. If 8 is the mean coefficient 
 
 h" 
 of absolute expansion of mercury at r°, h" would become — 
 
 when reduced to the temperature of the room, therefore the 
 corrected difference of level would be 
 h" 
 
 h'+ 
 
 i+8t 
 
 = ^' + A" ( I — 8 t) approximately, 
 
 = h' +k"-h"bT = h-k"hT. 
 
 We should have therefore to subtract from the numbers in the 
 second column a length obtained by multiplying the height of ' a ' 
 above the cork by 8, and by the corresponding excess of the 
 temperature of the water above the room. 
 
 44. Determination of the pressure of aqueous vapour 
 at temperatures above 100°. 
 
 Apparatus. Round-bottomed flask fitted with a two-holed 
 bung : Glass tubing 50 cm. . long : Narrow Glass Jar about 
 30 cm. high : Thermometer : Retort-stand : Bunsen Burner : 
 Mercury : Curve-papet. 
 
48 
 
 Practical Work in Heat. 
 
 Experiment. Bend the glass tube at right angles about 5 cm. 
 from one end. Ten centimetres from this bend, bend it again 
 at right angles in same direction. Fit the shorter limb into a 
 hole of the bung : into the other hole push the thermometer so 
 that its bulb nearly touches the surface of the water with which 
 the flask is half filled. Put in the flask a small piece of clean 
 coke to prevent boiling with bumping. Tie down the bung to 
 prevent its being forced out by the pressure of the steam. Place 
 the flask on a sand-bath on a ring of the retort-stand at a con- 
 venient height. Arrange the lower end of the bent tube so that 
 it nearly touches the bottom of the gas jar. Boil the water, and 
 noting the barometric height, H, find the temperature, T, at which 
 it boils. Pour into the jar some mercury until its level is about 
 2 cm. from the bottom. The tube should touch the side of the 
 jar so that its end may be seen through the glass. Heat the 
 water again until it boils "- Note the temperature 7^ , and 
 measure the distance h^ of the surface of the mercury above the 
 open end of the tube. The temperature, 7\, is the boiling point 
 under a pressure H+k^. Repeat this process, adding nearly 
 equal quantities of mercury each time. Enter your results in a 
 tabular form as follows : — 
 
 Barometric height, ff= . . . mm. 
 
 Boiling points. 
 
 Heights of mercury 
 above end of tube. 
 
 Pressures. 
 
 r 
 
 
 
 H 
 
 Plot a curve, taking the boiling points as abscissae, and cor- 
 responding pressures as ordinates. 
 
 " If a considerable quantity of steam condenses on the mercury it may be 
 occasionally got rid of by means of a large pipette. 
 
D. Evaporation. 
 
 49 
 
 Fig. 14. 
 
 46. Determine by Regnault's Hygrometer {a) the 
 pressure of the vapour in the air; (1^) the relative 
 humidity of the air. 
 
 [Take a boiling tube A from 2 to 3 cm. in 
 diameter and silver the bottom of it as described in 
 Appendix B. 8. Through a cork fitting this tube 
 pass a thermometer T and two elbow-tubes B 
 and C, one of which reaches almost to the bottom 
 of the boiling tube.] 
 
 Apparatus (Fig. 14). Aspirator. 
 
 Experiment. Pour some ether into the 
 Hygrometer so as to cover the bulb of the 
 thermometer when the cork is replaced. 
 Attach the elbow-tube B to an aspirator. 
 As the water flows out of the latter, air, 
 entering the tube C, bubbles through the 
 ether, which therefore evaporates quickly. 
 The external air is in consequence cooled 
 and its temperature is lowered to a point 
 at which it can no longer contain the vapour 
 existing in it. Therefore the vapour will condense, and at this 
 temperature (called the ' dew-point') it will exert its maximum 
 pressure. Read the temperature by the thermometer T, at 
 which the metal surface begins to be dimmed *° by the con- 
 densation of vapour. Stop the aspirator and read the tempera- 
 ture at which the dimness disappears. The average of the 
 two readings will give the dew-point approximately. Pass air 
 through the ether again, and stop when the thermometer is two 
 degrees above the approximate dew-point just founds Then 
 aspirate slowly, and stop every half degree watching for a 
 deposit of vapour. By this means a more correct value of the 
 dew-point is obtained ". Look in the tables for the maximum 
 
 *" It will assist in the detection of this film if, when its appearance is 
 suspected, a small part of the surface is wiped with a camel's hair brush, or 
 a momentary touch of the finger. If any dew is there, it will be wiped 
 away, and the contrast between the wiped portion and the rest of the surface 
 will be clearly seen. 
 
 "■ It is necessary that the observer should stand as far away from the 
 instrument as possible, so that the radiation from his body should not a£ect 
 the result. 
 
 £ 
 
50 Practical Work in Heat. 
 
 pressure f of water vapour at this temperature, which gives us 
 the pressure of the vapour in the air. 
 
 The humidity of the air is the ratio of the mass of vapour 
 present in a certain volume of the air to the mass of vapour this 
 volume could contain if saturated at the existing temperature. 
 
 f 
 This ratio can be proved to be the same as ■^' wherey is the 
 
 vapour-tension in the air (above found), and F the maximum 
 tension of vapour at the temperature of the air. The latter is 
 found also by referring to the tables [Appendix. A. lo]. The 
 
 percentage humidity is given by — x loo. 
 
 F 
 
 46. Betermination of the constant of a wet and dry 
 bulb Hygrometer. 
 
 Apparatus. Two thermometers : Vessel of water. 
 
 Experiment. Hang the two thermometers about lo cm. apart 
 from one another. Cover the bulb of one with fine muslin, to 
 which is attached a piece of loose cotton thread (such as is used 
 for the wick of an oil-lamp) long enough to dip into the small 
 vessel of water ^- The muslin and cotton are to begin with 
 thoroughly wetted with distilled water, then the water from the 
 cistern rises up the thread by capillary action, and the bulb is 
 thus kept constantly wet. 
 
 The two thermometers and small vessel of water ought to be 
 fixed to a wooden support and hung on the wall of the laboratory 
 in a permanent position. 
 
 In consequence of the continual evaporation the temperature 
 of the wet-bulb thermometer is always lower than that of 
 the dry-bulb thermometer. It is proved in books on physics 
 that 
 
 if t is the temperature of the dry-bulb thermometer, 
 /' the temperatinre of the wet-bulb thermometer, 
 F" the maximum pressure of water vapour at temperature /', 
 
 " The mnslin and lamp cotton should, before use, be boiled in water 
 containing a little washing soda to get rid of grease. 
 
D. Evaporation. 51 
 
 /"the pressure of the water vapour in the air, 
 
 and H the barometric height, 
 Hdr-o. f=F'—AH (t—t'), where A is the 'constant' of this 
 instrument. 
 
 To determine A, read /, f, and the barometric height H. 
 Look in tables for F', and find f by Regnault's Hygrometer 
 (Experiment 45). Substitute their values in the above equation, 
 and so determine A. 
 
 Having once determined A for the particular position in 
 which the instrument i^ always in future to be used, we can 
 evidently determine,/^ the vapour pressure in the air, ty reading 
 the dry and wet-bulb thermometers and the barometric height, 
 and finding the value of F' from the tables. 
 
 *47. Determination of the mass of 1 litre of Laboratory 
 air by reading the barometer, thermometer and hygro- 
 meter. 
 
 Apparatus, Thermometer: Hygrometer. 
 
 Experiment. The mass of a litre of laboratory air equals the 
 mass of the dry air added to the mass of the vapour contained 
 in it at the existing temperature and pressure. 
 
 Read the temperature / of the air, and the barometric height 
 H, and determine by Regnault's Hygrometer the pressure, yj 
 of the vapour in the air. 
 
 i. To determine the mass of a litre of dry air. 
 
 The dry air is at the temperature / and under a pressure 
 H—f When reduced to 0° and 760 mm. this volume becomes 
 
 ^x-^ litres. 
 760 273 + / 
 
 The mass of i litre of dry air at 0° and 760 mm. is 1-293 
 grams, therefore the mass of the above is 
 
 OTj = ^^^ X —-. X 1-293 grams. (i) 
 
 760 273 + / 
 
 ii. To determine the mass of a litre of vapour. 
 Reduced to 0° and 760 mm. this volume of vapour, which is 
 
 E 2 
 
5a Practical Work in Heat 
 
 at temperature / and pressure /, becomes 
 
 rf- X ^^/ litres, 
 760 273 + / 
 
 and since the density of water vapour is |ths of dry air, the mass 
 
 of the above vapour is 
 
 ^2 = 1^ ^ :7^lx> ^ 5 '^ ''■^^S grams. (ii) 
 
 700 273 + / 
 
 Adding (i) and (ii) together, we get for the mass of a litre of 
 the laboratory air, 
 
 H—if 273 
 M= m, + fn^ = "■' X ——-. X 1-293 grams. 
 760 273 + ' 
 
 Substituting for If,/", t we get M, the mass required. 
 
 E. Radiation. 
 
 48. To investigate Newton's Law of cooling. 
 
 Apparatus. Tin vessel about 200 c.c. capacity: Large 
 Beaker : Thermometer : Bunsen Burner : Curve-paper. 
 
 Experiment. Newton stated that when a heated body cooled 
 in an enclosure of constant temperature, its velocity of cooling 
 is proportional to its excess of temperature over that of the 
 enclosure. Let us take a thermometer as the body to te heated 
 and allowed to cool. In order to keep the temperature of the 
 enclosure constant take the tin vessel and float it in a large 
 beaker of water, so that the water level is about 2 cm. from the 
 top of the vessel on the outside — sand or shot may be used as 
 ballast. Take a piece of wood to be used as a cover, bore 
 a hole in the middle of it, and fit a cork, through which the 
 thermometer passes, to the hole. Take out the thermometer and 
 heat it carefully to about 70° or 80° in the hot air rising from 
 a flame. Replace it in the cork and arrange the cover so that 
 the thermometer dips into the empty tin vessel. Note the 
 
E. Radiation. 
 
 55 
 
 temperature every half minute as it cools down to the tem- 
 perature of the room, and enter your results as follows : — 
 
 Temperature of the enclosure / ... 
 
 Observed 
 temperature. 
 
 Excess of 
 temperature. 
 
 Average excess 
 every half minute. 
 
 Fall in degrees 
 every half minute. 
 
 Average excess. 
 
 Fall. 
 
 k 
 h 
 
 «3 
 
 fli + Sj 
 
 2 
 
 2 
 
 h-t. 
 
 ... 
 
 The numbers in the second column are obtained by subtract- 
 ing the temperature / of the water in the beaker from each of 
 those in the first column. 
 
 The numbers in the third column are the average of succes- 
 sive pairs of numbers in the second column. 
 
 The numbers in the fourth column are the differences be- 
 tween successive pairs in the first column. 
 
 The numbers in the fifth column are the quotients of cor- 
 responding numbers in the third and fourth columns., 
 
 If Newton's Law were true this last series would be constant. 
 It will be found, however, that as the temperature decreases the 
 numbers increase somewhat, which shows that Newton's Law is 
 not quite exact. 
 
 Plot your re'sults in a curve, taking the fall in degrees every 
 half-minute as abscissae, and the corresponding average ex- 
 cesses as ordinates. 
 
 49. To plot the curve of cooling for a calorimeter and 
 to determine how much heat is radiated in unit time 
 from it at a given temperattire. 
 
 Apparatus, Calorimeter : Thermometer : Bunsen Burner : 
 Curve-paper. 
 
 Experiment. Counterpoise the calorimeter. Boil some water 
 
54 Practical Work in Heat. 
 
 in a beaker, and pour some of it into the calorimeter so as to 
 very nearly fill it. Support a thermometer so that its bulb is 
 immersed under the surface of the hot water, and observe the 
 temperatures every half minute as the calorimeter cools to the 
 temperature of the room. At the end weigh the calorimeter and 
 find the mass, w, of water introduced. 
 
 Enter your results in a tabular form, and plot them on a curve, 
 taking the times as abscissae and the corresponding tempera- 
 tures as ordinates. This curve is called the cooling curve for the 
 calorimeter. It is independent of the nature of the liquid con- 
 tained in it. (Experiment 35.) 
 
 To determine the quantity of heat radiated in unit time at 
 a certain temperature, say at 50°. Through the point on the 
 temperature axis corresponding to 50° draw a horizontal straight 
 line cutting the curve at the point P. Through P draw a 
 tangent to the curve and continue it i to cut both axes. The 
 tangent of the angle this tangent makes with the time-axis 
 evidently gives us the rate of cooling at 50°; Let the tangent 
 cut the temperature axis at a point corresponding to a tem- 
 perature T, and the time axis at a point corresponding to N half- 
 minutes. Then at 50° it would cool T" \a. N half-minutes, 
 
 therefore — .in one half-minute. The quantity of heat radiated 
 
 depends on the mass and nature of the liquid in the calorimeter. 
 If m is the mass of water, and ju the water value of the calori- 
 meter, the quantity of heat given off at 50° during the half- 
 
 T 
 minute is evidently (wz-F/n) — 
 
 If we had filled the calorimeter with a mass m of another 
 liquid we should have to substitute ms in the above for m, where 
 s is the specific heat of the liquid. 
 
 Determine as above the quantity of heat radiated off by 
 (i) water, and {2) mercury at 40° from the same calorimeter. 
 
 The emissive power of a substance is that quantity of heat ' ' ' 
 
E. Radiation. 
 
 SS 
 
 emitted normally from unit area in unit time when its excess of 
 temperature is i° above that of the enclosure. 
 
 *^60. To compare the emissive power of two substances, 
 e. g. Lampblack and Tinfoil. 
 
 Apparatus. Two vessels of as nearly the same size and 
 shape as possible": Thermometer: Beaker: Bunsen Burner: 
 Curve-paper. 
 
 Experiment. Cover the outside of one vessel with lampblack 
 by holding it in an qjdinary gas flame. Fill it nearly with 
 boiling water and arrange the thermometer with its bulb im- 
 mersed in the water. Plot the cooling curve as in Experiment 49. 
 Now cover the outside of the other vessel to the same height 
 with strips of tinfoil, and plot its cooling curve on the same 
 piece of curve-paper, being careful that the water is at the same 
 height as in the first case. The emissive powers of lampblack 
 and tinfoil are evidently in the same proportion as the quantities 
 of heat emitted in unit time at the same temperature from equal 
 surfaces, i. e. in this case as their rates of cooling. Determine, 
 as in Experiment 49, their rates of cooling at varicftis tempera- 
 tures, and arrange results aa follows : — 
 
 Tempera- 
 tures. 
 
 T 
 
 T' 
 
 (i)H-(a) 
 £ 
 E 
 
 
 «^. 
 
 ... 
 
 ... 
 
 Plot a curve, taking the numbers in the second column as 
 abscissae and those in the third column as ordinates. 
 Compare the emissive powers of varnish, white lead, paper. 
 
 •^ Small conical flasks of about 80 c.c. do very well. 
 
56 
 
 
 Practical Work 
 
 in Heat. 
 
 
 Appendix A. 
 
 (I) 
 
 Volume of unit mass and 
 density of water at different 
 
 (2) 
 
 Volume of 1 c.c.ato° 
 
 and density of mercury 
 
 at different 
 
 
 temperatures. 
 
 temperatures. 
 
 i°C. 
 
 Volume of 
 unit mass. 
 
 Density. 
 
 Volume of' 
 I CO. at 0°. 
 
 Density. 
 
 
 
 I.OOOI 
 
 0-99988 
 
 I.oooo 
 
 i3^596 
 
 4 
 
 i.oooo 
 
 I -00000 
 
 1.0007 
 
 i3^586 
 
 10 
 
 1.0003 
 
 .99976 
 
 1.0018 
 
 i3^572 
 
 15 
 
 I'OooS 
 
 .99917 
 
 1.0027 
 
 i3^559 
 
 20 
 
 I.00I7 
 
 .99827 
 
 1.0036 
 
 13^547 
 
 25 
 
 1-0029 
 
 •997 '3 
 
 1-0046 
 
 i3^53S 
 
 3° 
 
 1.0043 
 
 •99578 
 
 1.0054 
 
 i3^523 
 
 35 
 
 1.0059 
 
 .99407 
 
 1.0063 
 
 13-5" 
 
 4° 
 
 1.0077 
 
 .99236 
 
 1.0072 
 
 13-499 
 
 45 
 
 1-0097 
 
 .99029 
 
 i-oo8i 
 
 i3^487 
 
 5° 
 
 I-0I20 
 
 ■98821 
 
 1-0090 
 
 1 3^474 
 
 55 
 
 I-OI44 
 
 .98580 
 
 1.0099 
 
 13.462 
 
 6o 
 
 I-OI69 
 
 ■98339 
 
 1-0108 
 
 i3^45o 
 
 bfi 
 
 1.0197 
 
 ■98067 
 
 1-0117 
 
 i3^438 
 
 70 
 
 1-0226 
 
 •97795 
 
 1-0127 
 
 13.426 
 
 75 
 
 1.0257 
 
 ■97495 
 
 I -01 36 
 
 13-414 
 
 8o 
 
 1-0289 
 
 •97195 
 
 1-0146 
 
 13-401 
 
 «5 
 
 10322 
 
 .96876 
 
 1.0154 
 
 I3^389 
 
 9° 
 
 1-0357 
 
 •96557 
 
 1-0163 
 
 i3^377 
 
 95 
 
 1-0394 
 
 .96212 
 
 1-0172 
 
 13-365 
 
 loo 
 
 1.0432 
 
 .95866 
 
 1-0182 
 
 i3^353 
 
 (3) Densities. 
 
 Lead ii-4 
 
 Iron 7-76 
 
 Copper 8-95 
 
 Glycerine 1-26 
 
 (4) Coefficients of Expansion 
 (absolute). 
 
 Glass (cub.) ? .000026 
 
 Zinc (lin.) .000029 
 
 Copper (lin.) .... -000016 
 
 Brass (lin.) -000019 
 
 Iron (lin.) 000012 
 
 Amyl Alcohol (cub.) . . -00109 
 Glycerine (cub.) . . . -000526 
 Turpentine (cub-) . . . -00105 
 Air (cub.) 00366 
 
 (5) Melting points. 
 
 Paraffin-wax 45° 
 
 Beeswax 62° 
 
 Stearic Acid ...... 69.9° 
 
 Benzoic Acid 121° 
 
 Tin 235° 
 
 Lead 335° 
 
 (6) Boiling points. 
 
 Methyl Alcohol 66-3° 
 
 Benzol 80-4° 
 
 Turpentine 156° 
 
 Ether 36-5° 
 
 Carbon Bisulphide .... 48° 
 
Appendix A. 
 
 51 
 
 (7) Specific Heats. 
 
 SnlphuT a34 
 
 Beeswax 64 
 
 Zinc 0935 
 
 Iron .112 
 
 Lead -osis 
 
 Copper .095 
 
 Ethyl Alcohol .6x5 
 
 Glycerine .555 
 
 Turpentine -467 
 
 Mercury 0333 
 
 Sulphuric Acid 33 
 
 Paraffin-wax 683 
 
 (8) ffeats effusion. 
 
 Ice 
 
 Beeswax 
 
 57.22 
 
 (9) Seats of vaporisation under a 
 pressure oflfio mm. of mercury. 
 
 Water 536 
 
 Methyl Alcohol 264 
 
 Turpentine 69 
 
 (10) Maximum pressure of aqueous vapour in mm. of Mercury. 
 
 t° 
 
 
 t" 
 
 
 t° 
 
 
 t° 
 
 
 t° 
 
 
 t° 
 
 
 
 
 4.6 
 
 II 
 
 9.79 
 
 22 
 
 19-66 
 
 45 
 
 71-39 
 
 99 
 
 733-21 
 
 100. 1 
 
 762-73 
 
 I 
 
 4.94 
 
 12 
 
 10-46 
 
 23 
 
 20.89 
 
 50 
 
 91.98 
 
 99.1 
 
 735-85 
 
 100.2 
 
 765.46 
 
 2 
 
 5-3° 
 
 '3 
 
 ii-i6 
 
 24 
 
 22.18 
 
 55 
 
 117.48 
 
 99.2 
 
 738-50 
 
 100.3 
 
 768-20 
 
 3 
 
 S-bg 
 
 14 
 
 ii-gi 
 
 25 
 
 23-55 
 
 bo 
 
 148-79 
 
 99-3 
 
 741.16 
 
 100.4 
 
 771-95 
 
 4 
 
 6-10 
 
 15 
 
 12.70 
 
 2b 
 
 24.99 
 
 05 
 
 186.94 
 
 99.4 
 
 743-83 
 
 100.5 
 
 773'7i 
 
 5 
 
 ("•sa 
 
 16 
 
 13-54 
 
 27 
 
 26.51 
 
 70 
 
 333-08 
 
 99-5 
 
 746.50 
 
 100.6 
 
 776.48 
 
 6 
 
 7.00 
 
 17 
 
 14.42 
 
 28 
 
 28.10 
 
 75 
 
 288.50 
 
 99.6 
 
 749.18 
 
 100.7 
 
 779.26 
 
 1 
 
 ?-49 
 
 18 
 
 15-36 
 
 29 
 
 29.78 
 
 80 
 
 354-62 
 
 99-7 
 
 751-87 
 
 100-8 
 
 782.04 
 
 8 
 
 8-02 
 
 19 
 
 10-35 
 
 30 
 
 31-55 
 
 «5 
 
 433-00 
 
 99.8 
 
 754-57 
 
 100.9 
 
 784-83 
 
 9 
 
 »-57 
 
 20 
 
 17-39 
 
 35 
 
 41-83 
 
 90 
 
 525-39 
 
 99-9 
 
 757-28 
 
 101 
 
 787-59 
 
 10 
 
 9.17 
 
 21 
 
 18.50 
 
 40 
 
 54-91 
 
 95 
 
 633.69 
 
 100 
 
 760.00 
 
 105 
 
 906-41 
 
 (11) Conversion Tables. 
 
 I centimetre = .39 inch. I inch = 2-54 centimetres. 
 
 1 sq. centimetre '=•155 sq. inch. i sq. inch =6-45 sq. centimetres. 
 
 I cub. centimetre =-061 cub. inch, i cub. inch = 16.386 cub. centimetres. 
 
 1 gram = 15.432 grains. i grain =.065 gram. 
 
 I kilogram =2.2 lbs. lib. =453.593 grams. 
 
 If t°, 6° represent the same temperature on the Centigrade 
 and Fahrenheit thermometers respectively, 
 
 e = |/+32; /= 1(0-32). 
 
 At 39° F or 4°C a cubic foot of water weighs nearly as 
 much as 62-4 lbs. At the same temperature i cub. cm. of water 
 weighs as much as i gram. 
 
58 Practical Work in Heat. 
 
 Appendix B. 
 
 1. Probable Error. When all the results of an experiment 
 are equally trustworthy, the probable value of the required result 
 is found by adding them together and dividing by the number 
 of the results, i.e. by finding their arithmetical mean. Let n be 
 the number of results 
 ^i> ^21 ^s) *^c. = their diiferences, 
 
 S = h^ + h^ + V + • • • or the sum of their squares, 
 then it can be proved that the probable error of the final 
 result is 
 
 = ± 0-6745 
 
 \J «(«— i) 
 
 2. To graduate and calibrate a glass bulb-tube and to 
 fill it with a liquid. 
 
 (a) To graduate it cover the whole of the stem with a uniform 
 thin layer of parafiin-wax. Fix it along a metre scale, and with 
 a fine needle make a scratch at intervals of -5 cm., and scratch 
 the numbers of every fifth division **. Brush some solution of 
 Hydrofluoric Acid over the tube and leave it for ten minutes. 
 The acid will etch the glass where it is exposed. Finally melt 
 off the wax and dissolve any that remains with ether. 
 
 [b) To calibrate it weigh the empty bulb-tube. Place it 
 
 with its open end under some clean dry mercury, and by 
 
 driving out the air by heat fill the tube partly with the 
 
 mercury, and allow it to cool to the temperature of the room. 
 
 Suppose the mercury reaches to the «*b division on the stem. 
 
 Weigh again and determine the mass, M, of the mercury it 
 
 M 
 contams. The volume of the bulb and the n divisions is — c.c, 
 
 O" 
 
 where o- is the density of mercury at the temperature of the 
 
 room. Therefore if B is the volume of the bulb [up to the point 
 
 where the divisions begin] and v the volume of one division, 
 
 M 
 B + nv = — • 
 
 " We suppose the tube to be of nniform bore. 
 
Appendix B. 59 
 
 Now introduce as before some more mercury, say up to the 
 «th division, and find the total mass, M', of the mercury con- 
 tained in the tube. Now we have 
 
 M' 
 B-\-mv = 
 
 From the above two equations we can find the volume B of the 
 bulb and v the volume of each division of the stem. 
 
 (f) A convenient method of filling the bnlb-tube is to support 
 it vertically. Connect the top of the stem by a short piece of 
 india-rubber tubing with a large funnel resting in a ring of 
 a retort-stand. Fill the funnel with liquid and heat the bulb 
 carefully with a burner. By this means the air is expelled and 
 the liquid can be made to fill the tube. 
 
 3. To graduate and calibrate a glass tube. Take 
 a narrow strip of gummed paper as long as the tube to be 
 graduated and mark off along it divisions -5 cm. apart. Stick 
 the paper along the tube. Take a short piece of the same 
 glass-tubing and smooth its ends flat on sand paper. Measure 
 its length, /. Counterpoise a crucible. Place the tube hori- 
 zontally under the surface of some clean mercury so that it 
 may be filled with it. Close the two ends by the fingers and 
 take the tube out of the mercury and transfer the mercury it 
 contains to the crucible. Weigh and find the mass, m, of the 
 mercury. Read the temperature, /, of the room. Find from 
 the tables the density o- of mercury at this temperature. Then 
 
 — is volume of a length / cm. of the tube, therefore the volume 
 
 <T 
 
 ftl 
 
 of each of the divisions on the graduated tube is —7— cubic cm. 
 
 2/0- 
 
 4. To clean and dry glass vessels. Rinse them out 
 successively with (i) Nitric Acid, (2) Distilled Water, (3) 
 Caustic Potash, (4) Distilled Water, (5) Alcohol. To dry 
 them take a piece of hard glass tube about 20 cm. long and 
 I cm. in diameter. Draw out one end so that it may be 
 sufiSciently small to insert in the vessel. Bend the tube 
 at right angles about g cm. from this end. Fix tube in a 
 
6o Practical Work in Heat. 
 
 clamp with bent end vertical, and allow the horizontal portion 
 to be heated by a large Bunsen. By means of india-rubber 
 tubing attached to the larger end of the glass tube and to a pa.ir 
 of bellows, cause a gentle current of hot air to pass into the 
 bottle, which must be placed resting mouth downwards on the 
 upright portion of the glass tube. A very useful piece of 
 apparatus for this and other purposes is the hand-bellows sold 
 by chemists to be used with a throat spray. 
 
 5. To clean mercury. A piece of clean writing paper is 
 folded twice at right angles and then opened out in the form of 
 a cone ; it is then fitted into a glass funnel. A few holes are 
 made with a fine needle near the apex of the paper cone, so 
 that when mercury is poured in the liquid escapes through these 
 in fine streams. Mercury filtered in this way is quite free from 
 dust. Another method is to pour the mercury into a handkerchief 
 and press it through the interstices of the linen. 
 
 6. To make a cork water-tight. Soak the cork thoroughly 
 in water and then place it in oil, and heat to about 120°. 
 
 7. Black Varnish. A good dead black varnish for radia- 
 tion experiments may be made by putting 2 grams of lamp- 
 black (or ' vegetable black ') into a mortar, weighing into the 
 vessel 8 grams of gold size, grinding the whole together into 
 a smooth paste and adding 10 grams of turpentine. . The whole 
 must be stirred thoroughly together just before use, and laid on 
 evenly with a soft brush. It adheres better if the surface is 
 slightly warmed previously, and heated more strongly after the 
 coating is applied. 
 
 8. Silvering Solution. Make two solutions as follows : — 
 {a) Two grams of silver nitrate are dissolved in 16 c.c. of 
 
 distilled water ; to this ammonia is added until the precipitate 
 first thrown down is almost entirely re-dissolved. The solution 
 is filtered and diluted to 200 c.c. 
 
 (b) Two grams of silver nitrate are dissolved in a little 
 ■distilled water and this is poured into a litre of rapidly boiling 
 distilled water, 1-66 gram of Rochelle salt (Potassium Sodium 
 
Appendix B. 6i 
 
 Tartrate) is added, and the mixture boiled for a short time till 
 the precipitate contained in it becomes grey. This is then 
 filtered while hot. The boiling tube to be silvered has to be 
 thoroughly cleaned inside with (i) Nitric Acid, (2) Distilled 
 Water, (3) Caustic Potash, (4) Distilled Water," (5) Alcohol, 
 (6) Distilled Water. Equal volumes of the above solutions are 
 mixed together and poured into the boiling tube up to the level 
 required to be silvered. In about an hour the silvering will be 
 complete. Pour off the exhausted liquid, rinse out with dis- 
 tilled water. Throughout the whole operation the most 
 scrupulous cleanliness i^absolutely essential. 
 
 9. Curves and Curve paper. Paper ruled in centimetres 
 and millimetres can be obtained from Messrs. Williams and 
 Norgate and Waterlow and Sons. The observed points of the 
 curve may be marked with small dots made with a hard sharp 
 pencil, and these may be marked by small crosses. In drawing 
 the curve the successive points may be first joined by thin 
 straight lines, and a smooth curve then drawn through them in 
 a freehand manner [see Note g]. 
 
Clarcnbon press iPublications. 
 
 Aldis. A Text-Book of Algebra : with Answers to the 
 Examples. By W. S. Alois, M.A. Crown 8vo, "js. 6d. 
 
 Bajmes. Lessons on Thermodynamics. By R. E. Baynes, 
 M.A. Crown 8vo, p. 6d. 
 
 Bonkin. Acoustics., By W. F. Donkin, M.A., F.R.S. 
 Second Edition. Crown 8vo, 7j. 6d. 
 
 Fisher. Class-Book of Chemistry. By W. W. Fisher, 
 M. A., F.C.S. Second Edition, Crown 8vo, 4r. 6d. 
 
 Hamilton and Ball. Book-keeping. New and enlarged 
 Edition. By Sir R. G. C. Hamilton and John Ball. Extra 
 fcap. 8vo, limp cloth, 2s. 
 
 Ruled Exercise books adapted to the above may he had, price is, 6d. ; 
 also, adapted to the Preliminary Course only, price 41/. 
 
 Hughes. Geography for Schools. By Alfred Hughes, 
 M.A. Part. I. Practical Geography. With Diagrams. Crown 
 8vo, 2^. id, 
 
 Minchin. Hydrostatics and Elementary Hydrokinetics. 
 By G. M. Minchin, M.A. Crown 8vo, loj. (>d. 
 
 Selby. Elementary Mechanics of Solids and Fluids. By 
 A. L. Selby, M.A. Crown 8vo, 7^. id. 
 
 Van 't Hoff. Chemistry in Space. Translated and 
 Edited by J. E. Marsh, B. A. Crown 8to, 4?. dd. 
 
 Oxfotft 
 
 AT THE CLARENDON PRESS 
 
 LONDON: HENRY FROWDE 
 
 OXFORD UNIVERSITY PRESS WAREHOUSE, AMEN CORNER, E.G. 
 
WORKS BY 
 
 R. C. J. NIXON, M.A. 
 
 EUCLID REVISED 
 
 CONTAINING THE ESSENTIALS OF THE ELEMENTS OF 
 
 PLANE GEOMETRY AS GIVEN BY EUCLID 
 
 IN HIS FIRST SIX BOOKS 
 
 Second Edition, Crown 8vo, 6s. 
 
 Supplement to Euclid Revised. 6d. 
 
 SOLD SEPARATELY AS FOLLOWS:— 
 
 Bool< 1. 1s. Books I and II. Is. 6d. Books l-IV. 3s. 
 Books V, VI. 3s. 
 
 GEOMETRY IN SPACE 
 
 CONTAINING PARTS OF EUCLID'S ELEVENTH AND 
 TWELFTH BOOKS 
 
 Crown 8vo, 3s. 6d. 
 
 ELEMENTARY PLANE TRIGONOMETRY 
 
 Crown 8vo, 7s. 6d. 
 
 O;i;fora 
 
 AT THE CLARENDON PRESS 
 
 LONDON : HENRY FROWDE 
 
 OXFORD UNIVERSITY PRESS WAREHOUSE, AMEN CORNER, E.G.