RICHARDS. — CALOMEL ELECTRODE. < 



SERIES II. 

 The Effect of Dilution. 



Hg - HgCl - ( HCl of varying strength) - HgCl - Hg. 



Strength of Solution. Temperature CoeflBcient between 20°-100°. 



Twice normal +0.000150 (?) 



Normal +0.000210 (?) 



Half normal +0.000250 (?) 



Fifth normal . - +0.000285 



Tenth normal +0.000324 



Twenty-fifth normal +0.000394 



Fiftieth normal +0.000438 



It is evident that the temperature coefficient increases rapidly with 

 dilution, as had already appeared from Series I. It is important, therefore, 

 to adjust carefully the strength of the solutions to be used. 



The effect of impurities and of mixing solutions was the next point to 

 be tested. This effect could naturally be observed most satisfactorily by 

 measuring cells containing mixtures of two electrolytes giving widely 

 different temperature coefficients when pure ; hence the third series of 

 results, for which potassic and hydric chlorides were used. 



SERIES III. 



The Effect of Mixed Solutions (Half Normal). 



Hg - HgCl - (KCl + HCI) - HgCl - Hg. 



From these figures it is evident that small amounts of impurities can 

 cause but slight differences in the result. The curve of changing tem- 

 perature coefficient is a regular and gradual one. 



