



^ > 



JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. Y may 4, 1915 No. 9 



PHY'SICAL CHEMISTRY.— r/ie reduction of iron oxides by 

 . platinum, with a note on the rnagnetic susceptibility of iron- 

 bearing platinum. R. B. Sosman and J. C. Hostetter, 

 Geophysical Laboratory. 



In the course of an investigation on the dissociation pressures 

 and melting temperatures of the oxides of iron, we have repeatedly 

 observed that the platinum crucibles used gained in weight and 

 became stiff, evidently through the absorption of iron from the 

 charges. 



Proof of the reduction of magnetite. The following experiment 

 demonstrates the absorption of iron from magnetite by plati- 

 num under a very low oxygen pressure. About 1 gram of nat- 

 ural crystalline magnetite from Mineville, N. Y., was heated to 

 500° in a new platinum crucible (Heraeus ''extra rein," dimen- 

 sions 18 mm high, 8-10 mm diameter) in a platinrhodium tube 

 vacuum furnace, ^ and then cooled. A small amount of gas was 

 given off and was not reabsorbed. This gas produced a pressure 

 of 0.045 mm in a volume of 1300 cc, and was probably nearly all 

 gas ''adsorbed" by the magnetite. This gas was pumped out, 

 and the charge then heated to various temperatures between 

 600° and 1200°. The temperatures were measured by a platinum- 

 platinrhodium thermo-element and potentiometer, and the pres- 

 sures were read on a 500 cc McLeod gage. A condensed record 



1 This Journal, 5: 277-2S5. 1915. 



293 



