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BURGESS AND WALTENBERG! PLATINUM 



presence of iron will lower the volatilization loss by amounts 

 depending on the quantity of iron present. There appears to 

 be no platinum made which does not contain some iron. 



5. The volatilization of platinum containing rhodium is less 

 than that of pure platinum at all temperatures above 900°C. 



6. The volatilization of platinum containing iridium is, above 

 900°C, very much greater than that of pure platinum, and 

 increases with the Ir content and with temperature. 



7. It appears to make no material difference in the volatili- 

 zation results, in the range 700° to 1200°, what is the order of 

 heating, ascending or descending temperatures. 



8. In an oxidizing atmosphere at temperatures of the order 

 of 1000°C, platinum, in the presence of but not in contact with 

 silica, will apparently take up small quantities of this substance. 



9. The loss in crucible weight due to the solution of soluble 

 matter in HC1, after heating, is variable depending on the cruci- 

 ble and may be large. This loss in relatively greater at low than 

 at high temperatures. 



10. All of the above losses, caused by heating, acid treatment, 

 and iron diffusion, apparently continue with undiminished 

 magnitude after the first treatment, which is usually erratic. 



11. The following table gives the approximate changes in 

 weight to be expected for heating platinum containing iridium 

 or rhodium but nearly free from iron. The presence of iron 

 in appreciable quantities renders the prediction uncertain but 

 it always acts in the direction of lowering the volatilization 

 loss. Silica, if taken up from the furnace, will also tend to lower 

 the results slightly. 



Approximate loss in milligrams per hour per 100 square centimeters at temperatures 

 indicated. Platinum nearly free from iron 



