I04 REPORTS ON INVESTIGATIONS AND PROJECTS. 



time, values of the latent heat of melting are few and far between, so that 

 no general discussion of this part of the subject is practicable now. This 

 reasoning can not, however, be applied to glasses ; for since they are merely 

 supercooled liquids, the latent heat of melting is zero, and hence, according 



to the equation -th, the change of melting-point with pressure is infinite. 



But this is not so contradictory as at first sight it may seem, for glasses behave 

 as liquids of exceedingly high viscosity, provided always that, conformably 

 with this high degree of viscosity, sufficient time be allowed for the motion 

 to take place. 



It has recently been established that a large number of apparently diverse 

 physical properties of a substance — melting-point, specific heats, coefficients 

 of thermal expansion and compressibility, electrical resistance — may be con- 

 sidered to be functions of a characteristic quantity, the molecular "vibration 

 frequency." Now, the flow-pressure, according to the equation discussed 

 in this paper, is a function of some of the above properties, and hence is a 

 function of the "vibration frequency." The existence of such a relationship 

 accounts simply for the parallelism between the calculated flow-pressures 

 and the mechanical properties of metals, for all of these quantities are 

 functions of the same characteristic parameter — a fact which indicates that 

 all the mechanical properties of metals will be found to be periodic func- 

 tions of their atomic weights, since the vibration frequency itself is doubt- 

 less such a periodic function. 



(13) Eine Beziehung der elastischen Eigenschaften der Metalle zu einigen ihrer physi- 



kalischen Konstanten. John Johnston. Z. anorg. Chem., 76, 361-379. 1912. 



A German translation of "A correlation of the elastic behavior of metals 

 with certain of their physical constants" (J. Am. Chem. Soc, 34, 788-802, 

 1912). Reviewed under No. 12 above. 



(14) The binary system: Na2Al2Si208 (nephelite, carnegieite)-CaAl2Si208 (anorthite). 



N. L. Bowen. Am. Jour. Sci. (4), 33, 551-573- 1912. 



The study of the system NagAlgSiaOg-CaAlaSioOg was undertaken be- 

 cause of the importance of these compounds as rock-forming constituents. 

 It was found that the soda compound exhibits enantiotropism with the in- 

 version point at 1248°. The low-temperature form (nephelite) crystallizes 

 in the hexagonal system with a habit similar to that of natural nephelite. 

 The high-temperature form is triclinic. It has no natural analogue and has 

 been given the name carnegieite. Carnegieite melts at 1526°. 



The lime compound occurs only in the triclinic form, anorthite, and melts 



^t 1550°. 



Both carnegieite and nephelite are capable of holding the lime compound 

 in solid solution, the former 5 per cent and the latter as much as 35 per cent. 



The effect of solid solution on the inversion-point was well shown by the 

 system. The temperature of inversion rises considerably as the amount of 

 the lime compound in solid solution increases. 



The optical constants of the components were carefully determined. 

 Crystals of the artificial nephelite were measured on the goniometer and 

 their hexagonal nature confirmed. It was especially gratifying to be able 

 to determine definitely the variation, with composition, of the optical prop- 

 erties of the hexagonal mix-crystals (nephelite). With increasing propor- 

 tion of the lime molecule the birefringence of 0.004 (negative) becomes less, 

 passes through zero, and finally becomes 0.002 (positive). 



