1889.] On the Detection of dissolved Chemical Compounds. 267 



bibasic, tribasic, and tetrabasic salts ; monobasic, bibasic, and tribasic 

 acids with all these classes of salts, and all these salts with each 

 other in similar great variety. And he concludes that the relation of 

 voltaic energy to chemical combining proportion, as already stated, is 

 a general one, and that every electrolytic substance when dissolved in 

 water unites chemically in definite proportions by weight with every other 

 such dissolved body, provided no separation of substance occurs. And 

 that they unite to form compounds of apparently unlimited com- 

 plexity. 



The method may be employed to ascertain the degrees of valency 

 of substances, the basicity of acids, &c. It may also be used to test 

 the purity of soluble bodies, and (as previously stated) to examine 

 the internal constitution of electrolytes ; and the author is now 

 using it for the two latter purposes. It is capable of extensive 

 application ; by it the state of union, whether chemical or of mere 

 mechanical mixture (possibly also the relative strength of chemical 

 union) of nearly every electrolytic substance soluble in water, 

 alcohol, &c., with every other such substance can be detected, pro- 

 vided the substances do not precipitate each other, or corrode the 

 platinum, and it would be easy to indicate a very large number of 

 mixtures which might be so examined, and thus lead to the discovery 

 of many definite compounds, probably thousands, which exist only 

 whilst in solution, and are decomposed on evaporating or crystallising 

 the solution ; he has already found more than 150. The author has 

 also employed it for ascertaining the distribution of acids and bases 

 when together in solution, and for measuring the rate of chemical 

 change proceeding in aqueous solutions, and generally for investi- 

 gating the chemical constitution of isomeric mixtures, or those 

 having the same ultimate chemical composition. All these results 

 have arisen from investigating the electromotive forces of simple 

 voltaic couples. 



As an illustration of the application of the method to the examina- 

 tion of the internal constitution of electrolytes, including that of 

 isomeric mixtures, two instances are given in which two mixtures, 

 possessing the same ultimate chemical composition, exert very different 

 amounts of voltaic energy. 



In an additional note, dated December 27th, 1888, the author 

 shows that although, according to J. Thomsen's determinations, an 

 aqueous solution of a molecular weight proportion of MgS0 4 , and 

 one of K 2 S0 4 , neither evolve nor absorb heat on admixture with each 

 other, distinct evidence of their chemical union whilst in solution is 

 afforded by measurements made with the "voltaic balance;" this 

 difference may perhaps be explained by the different degrees of 

 sensitiveness of the two methods. 



T 2 



