84 Proceedings of the Royal Society of Edinburgh. [Sess. 
forms. The ordinary dark-red ferric oxide is non-magnetic in fields 
of about 50 C.G.S., but a magnetic sesqui-oxide has been described by 
Malaguti,* and has also been mentioned by Hauser j* and Hilpert. Moissan 
has distinguished two allotropic forms of ferrosoferric oxide which are 
produced in hydrogen at 350° and about 1500° ; the former is black, has 
a density 4*86, and is turned into sesqui-oxide when heated on a platinum 
plate in air. The other form is also black ; its density is 5 to 5*09, and 
when heated in air it does not change into the sesqui-oxide. Moissan has 
also described two forms of ferrous oxide. That obtained at 600° has a 
great affinity for oxygen, with which it combines with incandescence to 
form sesqui-oxide. The other form of ferrous oxide is obtained at 1000° C., 
and is not inflammable. 
* Ann. Ghim. et Phys., iii. 69, pp. 214-224, 1863. 
t Ber. d. chem. Ges., xl. 2, pp. 1958-1960, 1907. 
{Issued separately March 24, 1913.) 
