abstracts: inorganic chemistry 629 



No definitely crystallized synthetic hydrated ferric oxide has up to 

 the present been prepared. However, it seems certain that only two 

 distinct types of "amorphous" hydrated ferric oxide exist, one yellow 

 and the other reddish brown. The yellow is apparently essentially 

 ferric-oxide monohydrate, while the reddish brown substance may hold 

 its water in either a dissolved or an adsorbed condition (or both). 

 Thus the synthetic and the natural hydrated ferric oxides exhibit, 

 chemically, great similarity. H. E- M. 



INORGANIC CHEMISTRY.— r/z<? ternary system CaO-MgO-SiOi. 



J. B. Ferguson and H. E. Merwin. Proc. Nat. Acad. Sci. 



5: 16-18. 1919. (Preliminary.) Amer. Journ. Sci. 48: 81-123. 

 Aug., 1919. 



The crystalline phases which are definite compounds and which ap- 

 pear as primary phases are as follows: Lime; magnesia; silica (tri- 

 dymite and cristobalite) ; cc-CaO.vSiO-i (pseudowollastonite) ; 3Ca0.2Si02; 

 a- and /3-2CaO.Si02; MgO.Si02 (clino-enstatite) ; 2MgO.Si02 

 (forsterite) ; CaO.Mg0.2Si02 (diopside); 5Ca0.2Mg0.6Si02; and 

 2CaO.Mg0.2Si02. The melting point of 2CaO.MgO.2Si.O2 is 1458° 

 ± 5°C. and the decomposition temperature of 5Ca0.2Mg0.6Si02 

 is 1365° =1= 5°C. In addition to these, crystals representing several 

 solid solutions also appear as primary phases. The solid solutions are: 

 I. A complete series with clino-enstatite and diopside as end members, 

 generally known as pyroxenes. 2. The pseudowollastonite solid solu- 

 tions. 3. The wollastonite solid solutions. 4. The 5Ca0.2Mg0.6Si02 

 solid solutions. 5. Certain members of the monticellite (CaO.MgO.- 

 Si02) solid solutions. Monticellite itself probably decomposes at 

 too low a temperature to ever occur as a primary phase. 



The temperature-concentration relations of the liquids which may 

 be in equilibrium with each of these phases have been thoroughly 

 investigated where necessary, by means of the quenching method, and 

 the results obtained have been correlated with the existing data on the 

 remainder of the ternary system. The compounds 5Ca0.2Mg0.6Si02 

 and 2CaO.Mg0.2Si02 (akermanite) have not been prepared previously. 

 Attempts to prepare a compound of the formula 8Ca0.4Mg0.9Si02 

 (Schaller's akermanite) gave negative results. The monticellite solid 

 solutions and the compound akermanite are discussed at length but 

 the wollastonite and the 5Ca0.2Mg0.6Si02 solid solutions are only 

 briefly mentioned as they are made the subject of a subsequent paper. 



