. The Philosophical magazine; a journal of theoretical, experimental and applied physics. irregular changeof electromotive force. It is j)robal)le that the curve obtainedby varying the temperature is characteristic of the substance,and would be diflferent with every ditferent substance anddegree of strcuigth of its solution. In a similar experiment with a solution of 027 grain ofchloride of ammonium in 465 grains of water, the electro-motive force of the zinc-platinum couple remained constantat 9084 volt at all temperatures between 14° and 100 C,and then very slightly increased. D. Curve by Va
. The Philosophical magazine; a journal of theoretical, experimental and applied physics. irregular changeof electromotive force. It is j)robal)le that the curve obtainedby varying the temperature is characteristic of the substance,and would be diflferent with every ditferent substance anddegree of strcuigth of its solution. In a similar experiment with a solution of 027 grain ofchloride of ammonium in 465 grains of water, the electro-motive force of the zinc-platinum couple remained constantat 9084 volt at all temperatures between 14° and 100 C,and then very slightly increased. D. Curve by Vakying the Temperature of the SolutionAT One Metal only. In these measurements the large bent glass tube was em-ployed (see section ■ B ). The liquid consisted of 39 grainsof potassium chloride dissolved in 465 grains of previouslyboiled distilled water. In one series of measurements thezinc was immersed in the heated portion of liquid and theplatinum in the cold portion ; and in the other series thereverse. The followino- are the curves obtained :— Fig. of KCl Zn at 17° ofPt varied. tt at 15° ol Zu varied. Centigrade J2degrees. Department of Chemical Research. 421 The two curves are very different. The greatest variationof electromotive force was at the zinc, and was = lOH volt,whilst that at the surface of the platinum was only = *04 volt. The results show that the change of electromotive forcewhich occurred on gradually heating an electrolyte and thetwo metals in it is a concrete effect of two influences, one ofwhich is situated at the surface of the positive metal and theother at that of the negative one. Each of these two in-fluences itself would also probably be a compound effect ofthe separate actions of heat upon the metal and upon theliquid. These general effects of variation of temperature describedin sections C and D are very similar to those of changeof strength of liquid given in sections A and B. E. General
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