Equilibrium in Mixed Electrolytes. 343 



In a more recent investigation, a On Changes of Electro- 

 motive Force, Volume, and Temperature by Mixing Electro- 

 lytes " (see Proc. Birm. Phil. Soc. vol. viii. p. 28) ,'I have further 

 shown that if, instead of a single mixture of two solutions, 

 a couple of such mixtures, isomeric with each other (for 

 instance H CI + NaBr, and HBr + XaCl) , was employed, under 

 certain conditions, in all the 25 cases of mixtures of Acids + 

 Salts and of Salts + Salts which were examined, the two 

 mixtures yielded the same amount of electromotive force, and 

 therefore formed the same final product during the act of 

 mixing ; in each case the ingredients of the two mixtures 

 started with different total amounts of energy, but arrived at 

 the same final molecular and chemical constitution ; each 

 different isomeric couple, however, gave a different final 

 amount. In other researches I found that if the solutions 

 were extremely dilute and the u voltaic balance " method was 

 employed, one of the two mixtures did not at once pass to the 

 same final state, but gave a very different amount of voltaic 

 energy from the other, especially if a free halogen formed 

 part of the mixture. A list of unstable mixtures, as found by 

 the voltaic balance method, has been given in a research on 

 the " Relative Amounts of Available Voltaic Energy of 

 Aqueous Solutions " (Proc. Birm. Phil. Soc. vol. vii. 1889, 

 p. 47). 



In the present research I have further examined the 

 circumstances which influence the conditions of instability 

 and of chemical and molecular equilibrium of such mixtures. 

 The circumstances examined are: — 1st, The influence of a 

 halogen and a salt ; 2nd, of a halogen and two salts ; 3rd, of 

 time upon the latter ; Ith, of heating such a mixture ; 5th, 

 of doubling the amount of the halogen ; 6th, of halving the 

 amount of the two salts ; 7th, of two different halogens and a 

 salt j 8th, of a halogen and an acid ; 9th, of two halogens and 

 an acid ; 10th, influence of one halogen and two acids ; 11th, 

 of halogens and an alkali with aluminium, tin, and zinc, as 

 positive metals ; and 12th, of heating the halogens with an 

 alkali. 



The method employed of measuring the electromotive 

 force was that of opposition with a thermopile of iron and 

 german silver and an astatic galvanometer, as in several of 

 the previous researches (see more particularly u A Method of 

 Measuring Loss of Energv due to Chemical Union, etc.," 

 Phil. Mag. Jan. 1892, p. 2S). The positive metal of the 

 voltaic couple used in the experiments of Tables I. to X. and 

 XIII. to XV. was of zinc, and in Table XL of aluminium, and 

 XII., of tin ; the negative metal in all cases was platinum. 



