858 



Again another problem originated from a publication of G. Fbiedel^), 

 who gave the description of a second modification of the metasilicate; 

 this new modification was jie\'er obtained either by Wallace ^), or 

 b}' Endell and Rieke, or b}- ourselves from a molten mass. On 

 the occasion of a renewed meltingpointdetermination, made by the tirst 

 of us') in 1910 at the Geophysical Laboratory in Washingto?i,3i new 

 indication of an eventually appeiiring inversion was not found; at the 

 same time it was once more demonstrated b}' this study, that even 

 in this relatively favorable case, where the liquid was highly movable 

 and the crystallization-velocity of the silicate could be considered as 

 exceptionally great, the "coolingmethod" was by no means adopted, 

 to give reliable and reproducible results. Other factors in the earlier 

 determinations, e.g. the use of crucibles and tubes of porous carbon, 

 and the insufiicient control of the variations in chemical composition 

 of the studied mixtures, caused by the volatility of the lithium-oxide, 

 and tinallj the impossibility to reduce the existing thermical data 

 to the scale of the nitrogengasthermometer, — seemed to us a series 

 of reasons, to take up a new study of this binary system by means 

 of the gradually developed exact methods "). 



§ 2. The necessary binary mixtures were prepared froui the 

 purest lithiumcarbonate and frcun pure, ground quartz of American 

 origin. The lithiumcarbonate was dried at 100° C ; there was a loss 

 of weight of only 0,057o- Only sodium could be detected spectros- 

 copically ; the quantity was however so small, that it could not be 

 determined by weight, using the amylalcohol-meihod. A trace of 

 iron was found also, but scarcely sufficient to give a reaction with 

 potassiumsulfocyanide as a pale pink colouring of the solution. The 

 lithium was weighed as lithiumsulphate; determined: 18,72*/o Li, 

 calculated: 18,797o Li. 



The quartz lost on heating on the blast no more than 0,01 7o ; 

 a small trace of iron, less than OjOS^/g, appeared to be the single 

 impurity. On evaporating with hydrofluoric acid in a platinum-dish, 

 no residue was left; the used quai'tz therefore can be considered as 

 pure SiOj. ') 



1) G. Friedel, Bull, de la Soc. Miner. 24, 14L (1801); Hautefeuille et Mar- 

 GOTTET, GompU Rend. 93, 6S6 (1881). 



2) R. C. Wallace, Zeils. f. anorg. Chemie, 63, 1 (1909). 



») F. M. Jaeger, Journ. of the Wash. Acad, of Sciences, 1, 49 (1911). 



*) F. M. Jaeger, Eine Anleitung zur Ausfiihrung exakter physiko-chemischer 

 Messungen bei liöheron Temperaturen. Groningen, 1913. 



^) Those preparations were supplied by Baker and Adamson; the used material 

 is the same as ui the Geophysical Laboratory in Washington, and employed for 

 standardizing purposes. 



