138 CARNEGIE INSTITUTION OF WASHINGTON. 



Although a normal lag effect characterizes even thick and heterogeneous 

 packings around a calorimeter, the loss of time due to the lag is a sufficient 

 objection to the practical use of anything which is not either very small or 

 in very close thermal connection with calorimeter or jacket. 



(30) The general character of specific heats at high temperatures. Walter P. White. 



Proc. Nat. Acad. Sci., 4, 343-346 (1918). 



The specific heats of three forms of silica and two silicates (alkali feld- 

 spars), determined for temperatures up to 1300°, indicate that the atomic 

 heats at constant volume for the substances increase above the theoretical 

 value 5.96, as the heats of metals have been known to do, and hence that 

 such increase is a very general phenomenon, as has been suspected. 



(31) Solubility and fusion relations at high temperatures and pressures. George W. 



Morey. J. Engineers' Club of PWladelphia, 35, 509-519 (1918). 



An address giving a popular discussion of the principles underlying the 

 solubility relations of binary systems composed of both volatile and non- 

 volatile components. In addition, some new compounds of the alkalies with 

 AI2O3 and Fe203 are described, as well as a new method for determining 

 solubilities under difficult experimental conditions. 



(32) Note on the sintering of magnesia. John B. Ferguson. J. Amer. Ceram. Soc, 1, 



439-440 (1918). 



The sintering of chemically pure magnesia has been generally regarded as 

 difficult if not impossible, and this note is intended to place upon record the 

 conditions under which such a sintering was found to take place readily. 

 Pure magnesia powder, upon prolonged heating at temperatures ranging 

 from 1600° to 1720° C, sinters to a cake of considerable mechanical strength 

 and this sintering is due to a recrystalUzation, forming a mass of interwoven 

 crystals, rather than to the presence of any bonding materials. 



(33) The effect of certain impurities in causing milkiness in optical glass. C. N. Fenner 



and J. B. Ferguson. J. Am. Ceram. Soc, 1, 468-477 (1918). 



In the manufacture of optical glass at the Bausch & Lomb plant, a matter 

 which gave considerable difficulty for a while was the occasional production 

 of pots of glass which were affected by opalescence or milkiness. The evi- 

 dence indicated that the source of the trouble lay in the sulphate and chloride 

 content of the Russian potash to which recourse was had when the German 

 supply was cut off, although certain facts tended to cast doubt upon this 

 conclusion. It was found, however, that the trouble disappeared when more 

 reliable methods of temperature-control were installed, by which an assur- 

 ance could be had of keeping the temperatures constantly at 1400° to 1420° 

 C, and when the Russian potash was replaced by an American product more 

 nearly free of impurities. Later, evidence was obtained which connected the 

 milkiness quite definitely with the impurities mentioned, at least as regards 

 the case under discussion, although in other cases the same effect is to be 

 ascribed to other causes. 



Reasons are given for the conclusion that the milkiness is caused not by 

 the separation of sulphates or chlorides themselves, but to some slight change 

 in the physical properties of the melt which permits the separation of clouds 

 of minute crystals of cristobalite. 



A discussion of this paper by Mr. F. Gelstharp, of the Pittsburgh Plate 

 Glass Company, and the authors is contained in the next succeeding number 

 of the Journal of the American Ceramic Society. 



