72 



very meager, the bibliography of the deposition of metals giving very little 

 light. 



Dr. William II. Walil. of I'hila(lel])hia. has written a pamphlet which 

 deals with the subject qualitatively and in a rather iudetinite manner. In 

 the investigation several problems presented themselves for solution, 

 among them being the following: 



I. The metal that shall be used for the cathode; 

 II. The solution of platinum to use for electrolyte; 



III. The current density tliat gives tlie best character of deposit at the 



most rapid rate: 



IV. The concentration of solution that gives best results; 



Y. The temperature that gives highest efficiency and best character of 



deposit; 

 \l. If the foil is porous or granular, the way to treat it so as to remedy 



tlie defect and get a dense, tougli deposit; 

 VII. The li(iuiil that will dissolve the metal of the catliode and leave the 

 jilat inum foil intact, 

 ^lost of tliese problems aic very closely related, so that results for 

 several were sometimes olitained from tlu' same set of experiments. 



<»n account of tlie smooth surface it will take, the ease with which it 

 in;iy lie dissolved, that it will take a deposit of another metal so readily, 

 and that it can be rolled into thin sheets, copper seems the best metal for 

 the catlidde. The anode, of com-se. should be platinmn, carbon or other 

 substance that will not be acted on by the nascent gas set free in the reac- 

 tion. 



II AND III. 



The salt of iilatintim used must be such that it is easily dissolved and 

 will start up no harmful secondary action during the passage of the cur- 

 rent. Platinic chloride will not serve on account of this last restriction, 

 riatinic hydrate, however, is almost ideal and was used in all experi- 

 ment!?. 



At first an effort was made to use platinic hydrate dissolved in oxalic 

 acid, forming oxalate of platinum, the proportions used being— 



1 oz. platinic hydrate, 



4 oz. oxalic acid, 



4000 c.c. distilled water. 



