Aqueous Solutions of Acids and Alkalies. 291 



gen, if in the proportions proper to form water, occupy ex- 

 actly the space of an equivalent weight of water. 



Other subjects than these are discussed in the memoir of 

 Messrs. Play fair and Joule, but in order to avoid complication 

 I shall confine myself entirely to what relates to the atomic 

 volume of substances in solution. 



If the first two of the foregoing propositions are true, they 

 give us important information respecting the constitution of 

 aqueous solutions. If, for example, we are furnished with 

 the specific gravities of anhydrous substances, and with their 

 atomic volumes in solution, then, knowing their atomic 

 weights, and taking for granted the specific gravity of water 

 and the temperature of the several materials, we shall have in 

 our hands the whole laws that regulate the specific gravities 

 of aqueous solutions, and we shall be enabled to calculate 

 tables of solutions perfectly free from the inaccuracies that 

 beset all tables that are prepared from experiments on indi- 

 vidual solutions. We shall be rendered by these doctrines 

 so completely master of details, that, if the specific gravity of 

 any solution be given, we shall be able to tell its chemical 

 strength ; or if the chemical strength be given, we shall be 

 able to declare what must be its specific gravity. These doc- 

 trines lead, therefore, to very important practical results, and 

 they are the more deserving of regard, that the previous re- 

 searches of chemists in this department have been entirely 

 unsuccessful. All that we know of the relation of the che- 

 mical strength of solutions to their specific gravity has been 

 derived from practical trials, and we have no general prin- 

 ciple to guide us beyond the limits of those trials, no rule by 

 which to test the accuracy of the experimental data, or by 

 which to determine either the chemical power of a solution 

 from its density, or the density from its chemical power. 

 The laws announced by Dalton, and reaffirmed by Messrs. 

 Playfair and Joule, come apparently to clear away this diffi- 

 culty, and coming supported by the results of a series of ela- 

 borate and ingenious experiments, if they are too startling to 

 command the immediate assent of chemists, they at least 

 merit a rigorous examination. 



In the course of an inquiry into the subject of centigrade 

 testing (dosage), I have had occasion to examine the consti- 

 tution of a great number of solutions of the principal acids 

 and alkalies. The facts elicited by that examination afforded 

 collectively a sharp test of the accuracy of these new doc- 

 trines respecting the atomic volumes of substances in solu- 

 tion. I compared therefore the doctrines with the facts care- 



