JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. I, AUGUST 19, 1911. No 3. 



PHYSICS. — Melting temperatures of sodium and lithium meta- 

 silicates. F. M. Jaeger. Communicated by A. L. Day. 



In studying the heating and cooling curves of the metasilicates 

 of sodium and lithium, I was led by the rapid rate of crystallization 

 of the lithium salt to investigate whether the temperature of 

 change of state of this salt might not prove a favorable constant 

 temperature for the calibration of thermoelements. No good 

 fixed point has yet been found for calibration purposes in the 

 neighborhood of 1200° C, intermediate between the copper point 

 (1082.6°) and the diopside point (1391°). 



The material was prepared by mixing the proper quantities 

 of pure lithium carbonate with a specially purified quartz and 

 grinding them together for some hours. After grinding, the mixed 

 powder was melted in a Fletcher furnace, cooled, and again ground 

 for six hours in an agate mortar. This process was repeated 

 three times to insure homogeneity. The analysis of the product 

 showed 67.2 per cent Si0 2 and 32.7 per cent Li 2 0, a loss of about 

 0.5 per cent of Li 2 0. A corresponding quantity of the lithium salt 

 was then added to the preparation and the mixture again ground 

 and melted alternately, three times, as before. Subsequent 

 analysis showed again a slight excess of silica and a third portion 

 of lithium carbonate was accordingly added. This preparation 

 when ground and melted three times gave a homogeneous mixture 

 as follows, the lithium being determined as sulphate: 



Analysis of lithium silicate 



Si0 2 66.60 K 2 none 



(Calculated 66.63 per cent) Na.0 0.51 



Fe 2 3 0.016 LioO 32.80 



CaO 0.034 (Calculated 33.37 per cent) 



FeO none 



49 



