92 abstracts: mineralogy 



as much as 1,000 times that of the magnesium. The essential feature 

 of the method here presented is the concentrating of the magnesium 

 into a precipitate containing but a small amount of calcium. This 

 concentrating is effected by precipitating Mg(0H)2 with a slight excess 

 of solid Ca(0H)2. The magnesium in this precipitate is determined 

 as pyrophosphate after removal of the calcium by two oxalate precipi- 

 tations. Determinations in some 30 highest-grade calcium salts show, 

 generally, far more magnesium than reported by the makers. J. C, HV 



MINERALOGY. — Das Studium der Mineralschmelzpunkte. Arthur 

 L. Day. Fortschritte der Mineralogie, 4: 115-160. 1914. 



A critical review of the work of recent years in the determination of 

 the melting temperatures of the minerals, in which an effort has been 

 made to clear up some of the confusion which now prevails in this 

 field of research. Some attention has been given to the applicabihty 

 of the laws of solutions to the change of state of minerals and to the 

 criteria available for the definition and experimental measurement of 

 those changes of state which can be competently studied with the meth- 

 ods and apparatus thus far developed. The effect of disturbing factors, 

 such as viscosity and inertia, which frequently intervene to delay or pre- 

 vent the establishment of equihl^rium in the system, and so compel the 

 use of methods of approximation, has also been considered, together 

 with the effect of admixtures of minor mineral components in natural 

 mineral types. A sharp distinction is drawn between the characteristic 

 properties of single minerals and of groups of two or more in solid solu- 

 tion. The failure to recognize and properly to appraise this distinction 

 appears to have been the cause of a considerable part of the confusion 

 alluded to above. 



Following these general considerations, several pages are devoted to 

 the description of the apparatus now in use in the various laboratories 

 for the determination of mineral melting-points, together with the limi- 

 tations encountered in its application to such studies and to the inter- 

 pretation of the results obtained with it. The effect of pressure upon 

 the change of state in minerals is also considered. The closing chapter 

 contains a table of all the melting temperatures of record, in which 

 appropriate attention has been given to the chemical purity of the 

 specimen studied. A. L. D. 



