156 CARNEGIE INSTITUTION OF WASHINGTON. 



for the eutectics, quintuple points, and boundary curves, together with the 

 corresponding temperatures. Owing to the large amount of data it will not 

 be possible to give in a paper of this nature more than the mean values 

 obtained from a large number of determinations of the various points. But 

 complete tables of data and a much more complete discussion of methods 

 and apparatus and of the results obtained will be given in a later monograph. 



(45) Das ternare System: CaO-Al203-Si02. G. A. Rankin; mit optischen Studien von 



Fred. Eugene Wright. Z. anorg. Chem. (In press.) 



A German translation of "The ternary system CaO-Al203-Si02" (Am. J. 

 Sci. (4), in press, 1914). Reviewed under No. 44 above. 



(46) Determination of cuprous and cuprie sulphide in mixtures of one another. Eugen 



Posnjak. J. Am. Chem. Soc, 36, 2475-2479 (1914). 



The reaction between cuprous sulphide and silver nitrate was confirmed in 

 accordance with the equation 



CU2S + 4AgN03 = AgaS + 2Ag + 2Cu(N03)2 



It was found that silver sulphide only, and no metallic silver, is formed by 

 the reaction between cuprie sulphide and silver nitrate, the equation for this 

 reaction being 



CuS + 2AgN03 = Ag2+ Cu(N03)2 



Based on the difference between these reactions, a method is given in this 

 paper for the determination of cuprous and cuprie sulphide in mixtures of the 

 two. The mixture is treated with silver nitrate and from the product the 

 metallic silver is extracted by means of ferric nitrate. The amount of cuprous 

 sulphide is calculated from the metallic silver, while the cuprie sulphide is 

 calculated from the difference between the silver in the silver sulphide and the 

 metallic silver. 



In mixtures containing the constituents in any proportion whatever, the 

 method was shown to be accurate within 1.5 per cent. 



(47) Measurements of refractive indices on the principal optical sections of birefracting 



minerals in convergent polarized Ught. Fred. E. Wright. J. Wash. Acad. Sci., 

 4, 534-542 (1914). 



On a given principal optical section of a birefracting mineral two of its 

 three principal refractive indices can be measured directly by the immersion 

 method. In the present paper several methods are considered for determining, 

 on the given section, the third refractive index of the mineral by means of the 

 phenomena observed in convergent polarized light. Mathematical equations 

 are derived which enable the observer to compute accurately the required 

 refractive index. Incidentally the exact thickness of the mineral section and 

 also the optic axial angle of the mineral can be computed by these methods. 



(48) Babingtonite from Passaic County, New Jersey. Clarence N. Fenner. J. Wash. 



Acad. Sci., 4, 552-556 (1914). 



The mineral babingtonite [(Ca, Fe, Mn)Si03 4-Fe2 (8103)3] is a rare species, 

 which has been found in few localities, and generally in very small crystals. 

 During the past summer the writer collected a small quantity of a mineral at 

 a basalt quarry at Great Notch, Passaic County, New Jersey, associated with 

 quartz, prehnite, zeolites, etc., which upon detailed examination has been 

 found to correspond to babingtonite. In addition to the rarity of the species 

 the chief feature of interest was the fact that the mineral was found as the 

 last remnants of crystals which had previously occupied cavities or casts of 

 large size among the associated minerals. These casts have long been familiar 

 to mineralogists and have been a source of much speculation. From their 



