JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. VI JUNE 19, 1916 No. 12 



PHYSICAL CHEMISTRY.— Further experiments on the vola- 

 tilization of platinum. 1 G. K. Burgess and R. G. Wal- 

 tenberg, Bureau of Standards. 



This is a continuation of an investigation 2 undertaken at the 

 suggestion of the Committee on "Quality of Platinum Uten- 

 sils" of the American Chemical Society. Seven platinum cruci- 

 bles of various makes and purity have been subjected to suc- 

 cessive heatings at 700, 1000, and 1200°C. followed by deter- 

 mination of iron and other materials soluble in 1 : 4 boiling- 

 hydrochloric acid. Among the results obtained are the follow- 

 ing: 



1. Platinum ware in the form of crucibles of whatever degree 

 of purity behaves, with respect to gain or loss of weight on 

 heating in air at ordinary atmospheric pressure, in a manner 

 characteristic only of the temperature of heating. 



2. Each impurity, as iridium, rhodium, or iron, appears to 

 exert its effect on the volatilization of platinum independently. 



3. For platinum crucibles of all degrees of purity containing 

 Ir, Rh, Fe, Si (up to a content of at least 3.0 per cent Ir) the 

 loss on heating is negligible below about 900°C. 



4. Below this temperature there may even be a slight gain 

 in weight on heating platinum, owing to the iron content diffus- 

 ing to the surface and oxidizing. At higher temperatures the 



1 To appear in detail as Bureau of Standards Scientific Paper No. 280 (Bull. 

 Bur. Stds., 13: 365 et seq.). 1916. 



2 Bureau of Standards Scientific Paper No. 254 (Bull. Bur. Stds., 26: 289-316. 

 1915) . This Journal, 5 : 378-380. 1915. 



365 



