88 Mr. H. C. Sorby on the Expansion of Water 



second difference is nearly uniform from 0° to 1 75°, but is de- 

 cidedly greater at 200°. Calculating, however, the formula as 

 before, from 25° to 175°, we obtain very different values for the 

 coefficients of ^ and t^, to those in the case of water ; for I obtain 

 the formula given below, which yields results compared with ex- 

 periment in the following Table : — 



V= -9997 + 000326/ + -OOOOOUl/^. 



In this case the agreement is very close from 0° to 175°, and it 

 is only at 200° that the difference is more than the probable 

 limits of error in observation. On comparing the formula with 

 that deduced for water, it will be seen that the coefficient of t is 

 much greater, whilst that of t- is much less than when no salt is 

 in solution, — thus proving that the expansion of the saline solu- 

 tion is much more uniform than that of water. In the case of 

 water, the expansion from 0° to 100° is to that from 100° to 

 200° as 1 to 2-64, whilst in the case of this saline solution it is 

 as 1 to 1-64. It will also be seen that, whilst the expansion of 

 the saline solution is greater than that of water from 0° to 100°, 

 it is much less from 100° to 200°. This is still more strongly 

 marked in the case of a solution of chloride of sodium in three 

 times its weight of water, as will be seen from the following 



Table :— 



Up to 100^ Up to 200°. 



Solution of NaCl . 1-0529 1-1328 



Water 1-0430 11566 



-I- 0099 --0238 



I have obtained similar results with various other saline solu- 

 tions; but I need not describe them in detail, for the general 

 facts will be shown sufficiently well by the following Table, in 

 which all the formulse arc compared together. They differ 

 from those given in my paper on the microscopical structure of 

 crystals*, because in it the apparent, and not the real expansion 

 was required. 



* Quart. Jouin. Geol. Soc, vol. xiv. p. 462. 



