146 CARNEGIE INSTITUTION OF WASHINGTON. 



other known form of AI2O3) could not be definitely established. Extensive 

 solid solution of AI2O3 in spinel was demonstrated. Only slight solid solution 

 was observed in any other crystals. Diagrams and a solid model were made 

 to show the relations found. 



(7) Daa ternarc Sj^stem: CaO-AljOs-MgO. G. A. Rankin und H. E. Merwin. Z. anorg. 

 Chem. (In press.) 



A German translation of "The ternary system CaO-Al203-MgO." (J. Am. 

 Chem. Soc, 38, 568-588, 1916). Reviewed under No. 6 above. 



(8j A universal switch for thermoelement work and other potential measurements. Walter 

 P. White. Am. J. Sci. (4), 41, 307-31G (1916). 



A switch combination is described which is intended to promote rapidity 

 (and, therefore, often accuracy also) in making comprehensive and varied 

 measurements with potentiometers. The type is characterized by the use of 

 contacts between thin copper strips, which is, thermoelectrically, perhaps the 

 best contact obtainable. A new mechanical arrangement greatly promotes 

 convenience and flexibility in operation. Other schemes make construction 

 and overhauling extraordinarily easy. 



(9) The charnockite series of igneous rocks. H. S. Washington. Am. J. Sci. (4), 41, 323- 



338 (1916). 



The name was applied by Holland to an important and interesting series of 

 igneous rocks in southern India, ranging from hypersthene granite (charnock- 

 ite) to hornblende hypersthenite. Five type specimens, furnished by the 

 India Geological Survey, v/ere studied and four complete analyses were made. 

 The rocks form a distinct series, characterized by certain constant mineral and 

 chemical peculiarities. Closely allied to the Indian comagmatic region are 

 those of western Norwaj^ Ellesmere Land, eastern Canada, New York State, 

 and the Ivory Coast. The relations of these are discussed and the suggestion 

 is made that the rocks of all these comagmatic regions can not be placed 

 logically in either the Atlantic or Pacific tribes of Becke and Harker. 



(10) The oxides of iron. I. Solid solution in the system FeaOs-FejO*. R. B. Sosman and 



J. C. Hostetter. J. Am. Chem. Soc, 38, 807-833 (1916). 



This investigation of the chemical relationships of the iron oxides has been 

 undertaken as a basis for the study of the iron-bearing silicates at high 

 temperatures. Measurements of the dissociation pressure of the iron oxides 

 were made in a vacuum furnace with a heating tube of platinum-rhodium. 



A study of the conditions of equilibrium shows that reproducible oxygen 

 pressures can be obtained at a given temperature. Equilibrium is attained 

 in a few minutes at high temperatures, although certain disturbing reactions 

 go on slowly. One of these by-reactions is the reduction of the oxide by plati- 

 num, yielding oxygen and an iron-platinum alloy. This reaction accounts 

 for the common occurrence of iron as an imi)urity in platinum. 



Ferric oxides from various sources jdeld practically identical pressures 

 (excluding certain minor exceptions which can not as yet be explained). The 

 same pressures are also attained with both rising and falling temperatures. 

 The oxidation of magnetite gives pressures which are identical with those 

 produced by dissociation of pure Fe203. 



The pressure-composition isotherm for the system Fe203-Fe304 at 1200° 

 indicates a continuous solid solution series from Fe203 over to a point very 

 near Fe304, if not over the entire range to Fe304. The opacity of the products 

 prevents an optical demonstration of the existence of solid solution in products 

 with more than 18 per cent FeO, but its existence can be shown optically in 



