CHLORPLATINIC ACID BY ELECTROLYSIS 577 



pended in a long cylinder when necessary so that it may be 

 brought to any desired temperature by surrounding it with wa- 

 ter. This outer tube is not shown in the figure and may be dis- 

 pensed with when low currents are used. When the current 

 rises to 10 amperes, the cooling jacket is essential to prevent the 

 apparatus from becoming hot. 



The reduced platinum to be treated is placed on the anode plate, 

 and is washed with dilute hydrochloric acid until clean. The 

 wash waters are drawn off through the siphon S. After wash- 

 ing, the platinum is covered with concentrated hydrochloric 

 acid, in quantity sufficient to have it stand in the tube on a level 

 with the end of S when the porous cylinder is inserted which 

 is filled to the top with hydrochloric acid. 



The current for electrolysis may be taken from a 120 volt 

 direct current by inserting a number of incandescent lamps par- 

 allel with each other and in series with the cell. The cell may 

 be run continuously on from eight to 10 amperes, and with this 

 strength 64 grams of platinum may be dissolved in four or five 

 hours. The theoretical quantity for 36 ampere hours is 65 

 grams. While the apparatus is in operation the hydrochloric 

 acid travels from the cathode cell to the anode under the in- 

 fluence both of gravity and electric endosmosis. By adjust- 

 ment of the hight of hydrochloric acid in the anode cell the 

 heavy layer of chlorplatinic solution as it is formed is delivered 

 at the tip of the siphon S drop by drop, or the flow may be 

 started by gentle suction at that point. The acid in the cathode 

 chamber is replenished from time to time as it becomes neces- 

 sary. Towards the end of the operation, when the amount of 

 platinum remaining on the perforated disk becomes small, bubbles 

 of chlorin commence to rise through the liquid, indicating that 

 the current density is becoming too great. This is remedied by- 

 placing fresh acid upon the platinum black and decreasing the 

 current. 



In concentrating the solution of chlorplatinic acid prepared in 

 this way, chlorin is passed through it for a short while to in- 

 sure freedom from platinous compounds in case any have been 

 formed during the electrolysis. 

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