370 



Mr. W. W. J. Nicol on the 



a strong solution the molecular volume of each salt-molecule 

 is greater than it is in a weak solution, owing to the attraction 

 of salt for salt having to a certain extent overcome the attrac- 

 tion of salt for water. If, however, the solubility of the salt 

 increases with rise of temperature, then the effect of heat will 

 be to weaken to a great extent the attraction of salt for salt, 

 and to a small extent that of salt for water; but the diminution 

 in the attraction of salt for salt may be so great as to be practi- 

 cally equal to an increase of the attraction of salt for water; and 

 such is the case with the solution of KN0 3 given above. On 

 the other hand, when solubility decreases with rise of tempe- 

 rature, then the attraction of salt for water diminishes faster 

 than that of salt for salt ; and this is to be seen in the case of 

 FeS0 4 above. 



Some experiments I have made on the coefficient of expan- 

 sion of concentrated solutions will make this even more clear. 

 I experimented with NaCl, KOI, NaN0 3 , and KN0 3 in nearly 

 saturated solutions at 20°, and determined their density at 

 20°, 40°, and 98° 0. The results and approximate strengths 

 of the solutions are given in Table IV. ; and the volumes at 



Table IV. 



Salt, 



S20°. 



S40°. 



£98°. 



n. 



NaCl 



1-19987 

 1-1827 

 1-14573 

 1-17311 



1-19614 

 1-18073 

 1-14107 

 1-16906 



1-19939 

 1-18602 

 1-13763 

 1-16668 



10-5 (c) 

 8-5 „ 

 5-5 „ 

 54- 



KC1 



NaN0 3 



KN0 3 



Wate 



r at 20°, 40°, and 98° taken as unity. 



Densit}^ re 



ferred to Water at 20° and Volumes. 



Salt. 



t°. 



**>■ 



Volume. 



Volume — 

 vol. of water. 



NaCl J 





 20 

 40 

 98 



1-19987 

 1-18911 

 1-15349 



100,000 

 100,905 

 104,021 



+312 

 + 42 



KC1 J 



20 

 40 



98 



11827 



1-17374 



1-14063 



100,000 

 100,763 



103,688 



4-170 

 -291 



NaNC-3 ...j 



20 

 40 



98 



1-4573 



1-13435 



10941 



100,000 

 101,004 

 104,720 



4-411 

 +741 



KNO3 | 



20 

 40 



98 



1-17311 

 1-16217 

 1-12203 



100,000 

 100,941 

 104,552 



+348 

 +573 





