430 EF. W. Clarke— Volume of Water of Crystallization. 
In this list it will at once be noticed that there is a consider- 
able variety of salts, varying in hydration from one to eighteen 
molecules of water. Chlorides, sulphates, both simple and 
double, nitrates, carbonates, borates, and acetates, are represented, 
Now, if we calculate from these data, the molecular volume of 
the water of crystallization in the manner already described, we 
shall get the following series of values: 
In CaCl,, 6 aq. 14°0 In CuK,(SO,)o, 6 aq. 14°1 
“ SrCl,, 6 aq. 13°7 “ ZnK,(SO,),, 6 aq. 14°5 
“Balls, 2 ag 13.2 “ CuAm,(SO,),,6 aq.  13°1 
“ FeCl,, 4 aq 13°3 “ ZnAm,(SO,),,6 aq. 13°2 
“ CoCl,, 6 aq 14°1 “ AIK(SO,),, 12 aq. 13°3 
* CuCl,, 2 aq. 12°5 “ AlAm(SO,),, 12 aq. 18° 
“Na, B,0,, 10 aq. 140 
74 CaSO Qa 13°9 . CaN ,O,, 4 aq. 15% 
(74 MnSO,, 5 Si 13°3 ve SrN.O0,;, 5 aq. 14 0 
* FeSO,, 7 aq. 14°1 
* CoSO,, 7 aq. 14°6 “ “Na, CO,, 10 aq. 15°0 
“ NiSO,, 7 aq. 14-7 “ CaCO,, 5 aq. 13°9 
* CuSO,, 5 aq. 13°3 “ KNaCOQ,, 12 aq. 13°4 
** MgSO,, 7 aq. 14°3 
“2080, 1% 14-2 “ NaC,H,Oz, 6 aq. 13°0 
Z 4> / aq. ‘ 
Al,(SO,),, 18 aq. 13°4 
The mean of all is 13°76. 
Here, now, we have practically one value for the molecular 
volume of water of crystallization, no clearly marked exception 
having yet appeared to me. When, instead of selected single 
determinations of specific gravity, the average of all the reliable 
published values for each salt is used in the work of calculation, 
the uniformity becomes, if anything, more striking. The dif- 
ference between the extremes in the above series of values 1s 
less than is frequently found between two determinations for 
one substance. 
When we consider the variety of salts with which we are 
dealing, and the great differences in the extent of their hydra- 
on, it seems certain that so remarkably uniform a series of 
— can be interpreted in only one way. 
) : ag 
en water unites with an anhydrous salt to become water oF 
to a volume of 13°76. An idea of the amount of this conden- 
sation may be derived from the fact that the molecular volume 
