300 Mr. G. Gore. Chemical Energy of Electrolytes [June 14, 



By regularly increasing the strength of the solution, the electro- 

 motive force at first increased very rapidly, then with decreasing 

 rapidity, and finally remained uniform. The total increase was 

 0"38 volt. The smallest proportion of bromine required to upset 

 the balance lay between 1 in 77,500,000 and 84,545,000 parts of 

 water. 



With each of these substances, and with all others which I have 

 examined, a gradual and regular increase of strength of the solution 

 from the weakest up to a saturated one, was attended by a more or 

 less irregular change of electromotive force. 



By plotting the quantities of dissolved substance as ordinates to 

 the electromotive forces as abscissae, each substance or mixture of 

 substances in every case yielded a different curve of variation of 

 electromotive force by uniformly changing the strength of its solu- 

 tion. With a given voltaic couple at a given temperature, the curve 

 was constant and characteristic of the substance. As the least addi- 

 tion of a soluble foreign substance greatly changed the "minimum- 

 point," and altered the curve of variation of potential, both the 

 curve and the minimum proportion of a substance required to upset 

 the voltaic balance may probably be used as tests of the chemical 

 composition of the substance, and as means of examining its state of 

 combination when dissolved. By varying the strength of the solution 

 at each of the metals separately, a curve of change of potential 

 was obtained for each positive metal, but not for every negative 

 one. 



III. " Influence of the Chemical Energy of Electrolytes upon 

 the ' Minimum Point ' and Change of Potential of a Yoltaic 

 Couple in Water." By G. Gore, F.R.S. Received June 7, 

 1888. 



In a communication to the Royal Society, May 3rd, 1888, on " The 

 Effect of Chlorine upon the Electromotive Force of a Yoltaic 

 Couple," and in a subsequent one on " The Minimum Point of 

 Change of Potential of a Yoltaic Couple," I have shown that by 

 opposing to each other two currents of equal electromotive force from 

 two perfectly similar couples of magnesium-platinum or zinc- 

 platinum in distilled water, and gradually adding to one of the cells 

 sufficiently minute quantities of a suitable substance, such as 

 chlorine, hydrochloric acid, or a soluble salt, &c, the voltaic balance 

 is not disturbed until a certain definite proportion of the substance 

 has been added, and that the proportion required to be added is 

 excessively small (about 1 in 17,000 millions) in the case of chlorine 



