210 Mr. S. Holker on Dr. Dal ton's new Method of 



And that when a class of isomorphous salts dissolved^ they oc- 

 casioned an increase or diminution of volume in a midtiple ratio 

 of the condensation or expansion occasioned by the several atoms 

 of those salts. And that when a class of isomorphous salts made 

 anhydrous, combined with the requisite quantity of water of cry- 

 stallizatioti, the condensation then occasioned was also in a mul- 

 tiple ratio. 



What I mean by condensation is, that when the joint bulk 

 of the salt and water is less than the sum of their bulks seve- 

 rally, and when there is a greater volume than the original 

 volume of the salt and water, there is an expansion. 



In making an experiment with one of the anhydrous salts, 

 *'for instance nitrate of potash," I took a certain quantity of 

 the nitrate well-dried and in fine powder, and dissolved it in 

 the 4-30 grains of water contained in the bulb and stem of the 

 apparatus ; 1 then suffered it to remain about half an hour 

 partly immersed in a vessel of water, with a piece of glass over 

 the opening of the tube to prevent loss by evaporation, in 

 order that the solution might absorb the requisite quantity of 

 heat to raise it to the temperature of 60° F. at which the room 

 was; as there is a certain quantity of heat rendered latent by 

 a salt dissolving in water, so that if the condensation occasioned 

 by the cold was not counterbalanced by the addition of the 

 requisite quantity of heat, the experiment would be incorrect. 

 In making an experiment with a hydrous salt, I proceeded 

 much in the same way as with the anhydrous, except that it 

 was dried by exposure to a temperature of about 60^ F., for 

 if the heat was raised higher, as in the case of the anhydrous 

 salt, some of the water of crystallization might probably have 

 been driven off. As by this mode of experimenting 1 could 

 only obtain the increase of volume when a certain quantity of 

 salt was dissolved in the 430 grains of water taken as a stand- 

 ard, and finding that most of my experiments, both on the 

 hydrous and anhydrous salts, did not correspond to the law 

 which Dr. Dalton had given, the only ones that did approxi- 

 mate being the sulphate of magnesia and carbonate of soda, as 

 stated before; I next proceeded to determine if the increase 

 of volume had any relation to the specific gravities of the dif- 

 ferent substances, or if, when a known weight of salt was dis- 

 solved in water, the increase of volume was in proportion to 

 the volume, as indicated by the specific gravity, and if so, the 

 salt would dissolve without either expansion or contraction. 



In trying if there was any relation of this kind, it was im- 

 portant to obtain the specific gravities of the different salts as 

 near the truth as possible. The way in which I found them 

 was as follows:— I have a botde witli u stopper, which when 



