332 Prof. Graham on Water as a Constituent of Salts. 



mens of these salts which I had occasion to examine, was there 

 any water of crystallization, and the evidence which is given 

 of its occasional presence is of a very doubtful description. 

 The crystals could be heated to 300°, without impairing their 

 transparency; and they fused at a temperature not under 600°, 

 without the loss of anything, except a trace of water, which 

 had been mechanically retained. Upon heating a bisulphate 

 nearly to redness, a portion of sulphate of water is expelled. 

 I greatly doubt whether water ever comes off in such a case 

 unaccompanied by sulphuric acid, although Berzelius appears 

 to be of a different opinion. It is well known that the sul- 

 phate of water is not entirely expelled from these salts by heat 

 alone, even the most intense. Sulphate of water, however, 

 leaves the sulphate of soda with greater facility than it leaves 

 the sul()hate of potash. 



These sulphates should be crystallized from concentrated 

 solutions at a high temperature; for their solutions are very 

 apt to undergo decomposition at low temperatures, the neutral 

 sulphate crystallizing, and leaving " the sulphate of water with 

 saline water" in solution. I have often observed this decom- 

 position to occur, even in solutions containing a great excess 

 of sulphuric acid. At low temperatures, therefore, the affinity 

 of sulphate of water for " saline water," prevails over its affi- 

 nity for sulphate of potash. Crystals of bisulphate of soda, 

 pounded and put under pressure in blotting paper, are apt to 

 undergo the same decomposition, if the air is damp, and fre- 

 quently impart a large quantity of their sulphate of water to 

 the paper in the course of twenty-four hours. This circum- 

 stance must be kept in view in preparing bisulphates for ana- 

 lysis. The facility with which these salts are decomposed 

 by water, accords well with their relation to sulphate of water 

 with saline water, which we have supposed to exist. Sulphate 

 of zinc, sulphate of magnesia, &c. are capable of separating 

 the sulphate of water from these salts, at a temperature ap- 

 proaching to redness, and take its place. 



I have observed that the bisulphate of soda is more prone 

 to decomposition, when dissolved in water, than the bisul- 

 phate of potash. The double salts of sulphate of soda with 

 sulphate of magnesia, &c., are also much less stable than the 

 corresponding double salts containing sulphate of potash. 

 Indeed, I believe that the former are uniformly decomposed 

 when dissolved in water. 



Sulphate of Potash, Sulphate of Soda, KS, NaS. 

 These salts differ from other sulphates in having no saline 

 water. Of the ten atoms water with which sulphate of soda 



