58 



MR J. Y. BUCHANAN ON THE 







Quantity of Salt 

















Hydro- 

 meter 

 used. 



Number 

 of Experi- 

 ment. 



in 1000 grams 



of Water, 



expressed in 



gram-molecules. 



m. 



Initial Air 

 Tempera- 

 ture. 



Initial 

 Solution 



Tempera- 

 ture. 



Time of 

 Commence- 

 ment of 

 Experiment. 



Final Air 

 Tempera- 

 ture. 



Final 

 Solution 

 Tempera- 

 ture. 



Time of Com- 

 pletion of 

 Experiment. 



Duration 

 of Experi- 

 ment in 

 M-inutes. 









°C. 



°C. 





°C. 



"C. 







No. 17 



1 



1 



19-20 



19-50 



11.3 a.m. 



19-30 



19-50 



11.16 a.m. 



13 



„ 3 



2 



J) 



19-30 



19-50 



11.20 „ 



19-30 



19-50 



11.34 „ 



14 



» 17 



3 



fy 



19-30 



19-50 



11.40 „ 



19-30 



19-50 



11.54 „ 



14 



„ 3 



4 



)j 



19-30 



19-50 



11.59 „ 



19-30 



19-50 



12.12 p.m. 



13 



„ 17 



5 



}) 



19-30 



19-50 



12.17 p.m. 



19-30 



19-50 



12.31 „ 



14 



„ 3 



6 



)) 



19-30 



19-50 



12.36 „ 



19-30 



19-50 



12.50 „ 



14 



No. 17 



7 



1 



19-30 



19-50 



1.45 p.m. 



19-30 



19-50 



1.57 p.m. 



12 



„ 3 



8 



)J 



19-30 



19-50 



2.5 „ 



19-30 



19-50 



2.17 „ 



12 



» 17 



9 



J) 



19-30 



19-50 



2.22 „ 



19-30 



19-50 



2.34 „ 



12 



,, 3 



10 



)J 



19-35 



19-50 



2.45 „ 



19-35 



19-50 



2.59 „ 



14 



„ 17 



11 



)? 



19-30 



19-50 



3.4 „ 



19-35 



19-50 



3.16 „ 



12 



„ 3 



12 



J) 



19-30 



19-50 



3.22 „ 



19-30 



19-50 



3.35 „ 



13 



„ 17 



13 



)! 



19-30 



19-50 



3.42 „ 



19-30 



19-50 



3.56 „ 



14 



It will be seen that the initial and final solution temperatures were constant to 

 within 0'01° C. throughout the series of experiments. There were slight variations in 

 the air temperature of the room, the widest range being from 19"20° C. to 19"35° C. 

 The rise was occasioned by turning on the radiator full for a few minutes and opening 

 the door for fresh air, but no change occurred in solution temperature, so that latitude 

 can be given in the range of air temperatures ; but from experience it is not advisable 

 to go below 19 '2° C. unless direct radiation can be supplied to the solution, as shown in 

 the earlier part of this section, the source of which can be effectively controlled. 



In the conditions which obtain in this laboratory, it is possible to conduct a series 

 of experiments extending over the day and to maintain the temperature of each 

 solution constant for at least fourteen minutes if the temperature of the air is kept 

 0*3° lower than that of the solution. 



§ 25. While the conditions which have been described are all essential for complete 

 success in hydrometric work from the point of view of constant temperature, it may, 

 and does occasionally, happen that, even after adopting all the precautions mentioned 

 above, a series of observations will be taken, and then the solution temperature will be 

 found to have changed, and with this change there has been a deviation in the value of 

 specific gravity, certainly in the most extreme case amounting to only a few units in 

 the 5th decimal place ; but the deviation coupled with the temperature change has, 

 in the most recent work, justified its elimination from the remaining series of observa- 

 tions which are perfect, in that the results of the other series agree iriter se and no 

 change in solution temperature has occurred. 



An example of such an occurrence happened on 4th April 1911, when a series of 

 hydrometric observations was made upon a solution containing ^ gram-molecule NaCl 

 in 1000 grams water. It was the first series of the day, and although the initial and 

 final air temperatures for this experiment were both 19 "30° C, the solution temperature 



