2U 



Dr. G. Gore. On the 



[Dec. 16, 



VI. " On the Thermo-Electric Behaviour of Aqueous Solutions 

 with Platinum Electrodes. 5 ' By G. Gore, LL.D., F.R.S. 

 Received November 13, 1880. 



The object of the following research was to enable a comparison to 

 be made of the results obtained in a previons investigation with 

 mercurial electrodes (see " On the Thermo-Electric Behaviour of 

 Aqueous Solutions with Mercurial Electrodes," " Proc, Roy. Soc," 

 vol. 29) with those of platinum in similar liquids, in order to ascer- 

 tain whether the results further confirmed the conclusion that the 

 currents obtained with mercury were not at all due to chemical action ; 

 and also to draw from the results such additional inferences as were 

 warranted. The results of a former research, in which platinum elec- 

 trodes were employed in a different apparatus (see " Proc. Roy. Soc," 

 vol. 27) could not be used for the purpose of comparison, because it 

 was found necessary to use weaker solutions with mercurial electrodes 

 (in order to avoid chemical action) than those used with platinum in 

 that research. 



The apparatus employed in the present investigation was precisely 

 similar to that used in the one with mercury, with the exception that 

 coiled ribbons of sheet platinum (with attached wires of that metal) 

 were substituted for the layers of mercury. , 



The platinum ribbons were 27*5 millims. wide, and each had a total 

 surface of 52,960 sq. millims., including both sides. They were 

 prepared for use at the outset by heating them to redness. Between 

 each experiment it was found necessary to thoroughly wash them, 

 then immerse them in boiling distilled water during about ten or 

 fifteen minutes, drain and dry them. They were then simultaneously 

 immersed in the liquid to be tested, the latter being at a temperature 

 of about 55° E. A slight temporary deflection of the needles of the 

 galvanometer was usually produced on immersion ; when the needles 

 had settled at zero, heat was applied to one of the vessels, and it& 

 temperature raised to 180° E., the deflection being noted. After the 

 experiment had been made, the two portions of liquid were mixed and 

 cooled. 



As this research was made chiefly for the purpose of comparing the 

 thermo-electric behaviour of liquids with mercury to that with 

 platinum, precisely similar liquids were employed to those used in the 

 investigation referred to. None of the solutions acted chemically (in 

 any perceptible degree) upon platinum. It was found necessary to 

 preboil the solution about half-an-hour, in order to expel dissolved 

 air ; otherwise the deflections obtained in repetition experiments were 

 not uniform. It was also found necessary to occasionally immerse the 

 ribbons in a boiling-hot dilute solution of pure potassic hydrate, during 



