Measuring the Water of Crystallization of Salts. 215 



relation which appears to exist in some of the salts might be 

 brought to coincide much more perfectly than it does at pre-^ 

 sent; but as this paper is designed only as an introduction to 

 a research which at a future time I hope to complete in a more 

 satisfactory manner, I have merely stated the direct results of 

 ex})eriments without obtaining data requisite for allowances, 

 which hereafter I might find to be incorrect. 



To ensure accuracy in the above experiments, it was neces- 

 sary to obtain the various kinds of salts perfectly free from 

 impurity^ and having analysed some of them, they were found 

 to contain the same quantity of acid, base and Water, as indi- 

 cated by Dr. Turner's Chemistry; and most of the others 

 being tried with the several tests for impurity in such salts, 

 Were found to contain no appreciable quantity. The way I 

 calculate the amount of condensation occasioned by a salt made 

 anhydrous combining with the requisite portion of water of 

 crystallization, is as follows:-^ 



Let X = the amdUtit of condensation occasioned by the an- 

 hydrous salt. 



W = the weight of crystallized salt. 



V = the volume of crystallized salt. 



C = the condensation resulting from the solution of the 

 crystallized salt. 



B = the weight of the water of crystallization. 



E = the increase of volume that the salt deprived of its vfater 

 of crystallization occasions in solution. 



A = the weight of anhydrous salt. 



Then (W-B) = A; therefore ^ = (V-C-E) = the con- 

 densation produced by A. To give an example : — If 123 grains 

 of sulphate of magnesia, specific gravity 1*665, condense in 

 solution 6-87 grains by measure, the water of crystallization 

 being 63 grains; and 60 grains anhydrous sulphate increased 

 4*16 grains by measure, required the amount of condensation 

 occasioned by the anhydrous sulphate. 



ThenA = (123 — 63) = 60, therefore ^-rr (73-87 — 6-87 — 4.-16) 

 = 6284 grains measure, the amount of condensation produced 

 by the 60 grains of anhydrous sulphate combining with the 

 Requisite portion of water of crystallization to form 123 grains 

 of crystalline salt. 



I have drawn out a table, partly theoretical, of most of the 

 isomorphous salts used in the experiments^ being chiefly di- 

 rected by the composition to show the multiple relation that 

 appears to exist in each order. 



' The discrepancies that occur in this proportion may be very 

 reasonably accounted for, as they are not so great as to excite 

 a doubt as to the accuracy of the law, by supposing that the 



