■74 



With a solutiou in tbe proportions of 

 2 oz. platinic hydrate, 



4 oz. caustic potash, 

 2000 c.c. distilled water, 



it was foirnd possible to run the current density up to .006 amperes. 

 With another solution in which the proportions were 



5 oz. platinic hydrate, 

 8 oz. caustic potash, 

 4000 c.c. distilled Avater, 



the current reached .012 amperes before the appearance of platinum 

 black. 



Increasing the platinic hydrate in tlie above so as to have 6 oz. plat- 

 inic hydrate, increased the current density to .015 amperes per square 

 centimeter. The amount of caustic potash was increased so as to make 

 a solution having the proportions— 

 2 oz. platinic hydrate, 

 1 oz. caustic potash, 

 4000 c.c. distilled water, 

 when it was found that .002 amperes was as high as the current density 

 could be caiTied. Increasing the amount of caustic potash still further 

 decreased the amount of current that could be used. 



From the results given it may be concluded that the greater the per 

 cent, of platinum in the solution, the higher the current density that can 

 be used. Any Increase in the amount of caustic potash lessens the maxi- 

 mum current density. 



V. 



In regard to the temperature that gives the best results, the experi- 

 ments showed that any increase in the temperature raised the maximum 

 current density that could be used. Thus, at 65 F. .0035 amperes per 

 square centimeter was the maximum, while a temperature of 100 F. per- 

 mitted the use of a current as high as .008 amperes per square centimeter, 

 with corresponding changes for intermediate points. 



