532 SOSMAN AND MERWIN: LIME: FERRIC OXIDE 



CHEMISTRY. — Preliminary report on the system, lime: ferric 

 oxide. R. B. Sosman and H. E. Merwin, Geophysical 

 Laboratory. 



Previous work. Apart from various isolated observations on 

 the calcium ferrites, the only extensive investigation of the 

 system calcium oxide: ferric oxide has been by Kohlmeyer. 1 He 

 observed the melting and freezing temperatures of 44 mixtures, 

 containing from 5 up to 95 molecular per cent CaO. The 

 density and external crystal form, as well as the chemical behavior 

 toward water, carbon dioxide, etc., of the products, were also 

 determined. Unfortunately no optical examinations were made, 

 and no optical properties measured. 



Experience has shown that in the study of such systems as 

 the silicates and ferrites the assistance of the petrographic micro- 

 scope is almost indispensable; false conclusions may easily be 

 reached from thermal data alone. Such was the case with Kohl- 

 meyer's study. We have proved the existence of only one out 

 of his five supposed compounds, while we have found one new 

 compound, the existence of which was not shown by his thermal 

 data. 



Dissociation of the ferric oxide. A certain amount of ferrous 

 iron is formed in all melted mixtures of CaO and Fe 2 3 . Between 

 50 and 100 molecular per cent CaO the percentage of ferrous 

 oxide is small in mixtures heated to 1400°-1500°; but in melts 

 containing from to 50 per cent CaO the amount of ferrous 

 oxide increases rapidly with the temperature and with the pro- 

 portion of Fe 2 3 , so that some of the melting and solidifying 

 points observed may actually belong in the three component 

 system : lime-iron-oxygen. The completion of the diagram from 

 to 50 per cent CaO will therefore have to await experiments 

 under oxygen at pressures higher than atmospheric. 



Since apparatus for such experiments is not immediately avail- 

 able, and since the results already obtained are of some interest, 

 particularly in connection with certain problems of Portland 



1 Diss., Berlin 1909. Ber. Don. Chem. Ges., 42: 4581-4594. 1909. 



