the Cation in Voltaic Combinations. 459 



method were employed as with iodine chloride. The results 

 are given in Table II. The BrCl aqueous solution was 

 saturated and all the others were strong solutions. 



22. A number of tentative experiments were made with 

 chlorides of sulphur and phosphorus &c, in attempts to con* 

 stitute cells in which the chlorine might combine with a 

 positive plate of zinc or other metal, and the sulphur or phos- 

 phorus be oxidized by an appropriate oxidizing cathode. 

 The following substances were tried between zinc and plati- 

 num plates or zinc and manganese dioxide. They are all, 

 however, almost, if not quite, nonconductors, and it was 

 therefore impracticable to measure definitely their electro- 

 motive forces. They appeared to be all considerably under 2 

 Daniells. 



Sulphur chloride, S 2 C1 2 . 



Same dissolved in carbon bisulphide. 



Same after passing dried chlorine into it until it assumed 

 the red-brown colour of SC1 2 . 



Double chloride of tin and sulphur, SnCl 4 2SCl 4 . 



Phosphorus trichloride, PC1 3 . 



Same dissolved in benzol. 



Same after passing hydrochloric-acid gas through it. 



Double chloride of iodine and phosphorus, PIC1 6 , dis- 

 solved in phosphorus trichloride, PC1 3 . 



Phosphorus iodide, PI 2 , in carbon bisulphide, CS 2 . 



23. In Tables I. and II. the values under the head of Theo- 

 retical Electromotive Force (except 1 8 and 20) are obtained by 

 taking the difference of the combining heats, in aqueous solu- 

 tion, of the positive and negative plates with the anion of 

 the electrolyte, chlorine (Cl 2 ) subtracting twice that of iodine 

 chloride (I, CI), or bromine chloride (Br, CI), and dividing 

 by the thermochemical value of the Daniell taken as 50,130. 



If P = positive plate, N = negative plate, A = anion, and 

 = cation, and using the comma-divided symbols as signify- 

 ing their respective heats of formation, the theoretical electro- 

 motive force E 1 will be 



P, A-A, C-A, N 



E 1 = 



50,130 



The heats of combination are, with one exception, Thorn- 

 sen's, taken from the tables in Muir and Wilson's ' Thermal 

 Chemistry/ 



24. In comparing the observed and theoretical values, it is 

 to be noted that in the latter no account is taken (except in 

 18 and 20) of the combining heat of the cation (iodine or 

 bromine) with either positive or negative plate, and the 



