552 1ST. L. Boioen — The Binary System. 



from all but the last trace of alkalis by boiling with, a solution 

 of ammonium chloride and igniting. A very pure silica was 

 obtained by grinding selected quartz and treating with hydro- 

 chloric acid. Anhydrous sodium carbonate was made from 

 the hydrated compound by heating for eight hours at 300°C. 

 It was proved that the material so obtained corresponded with 

 the formula Na 2 0O 3 by converting to chloride and weighing. 



To make anorthite CaC0 3 , A1 2 3 , and Si0 2 were mixed in 

 the proper proportions and fused in a Fletcher gas furnace at 

 about 1600°. Three fusions, the product being finely ground 

 before each, gave a glass which crystallized to a perfectly 

 homogeneous mass of anorthite. 



In the preparation of the soda compound JS"a 2 C0 3 , A1 2 3 , and 

 Si0 2 were mixed and the same procedure followed, but not 

 with equal success. When the resultant glass was crystallized, 

 instead of the homogeneous product to be expected, the micro- 

 scope showed, scattered throughout, plates and needles of A1 2 3 

 (corundum) uncombined. Repeated fusion did not remedy 

 the difficulty. Finally, it was determined by analysis of the 

 glass that some Xa 2 had been volatilized at the high tempera- 

 ture of the gas furnace. The materials had been mixed in the 

 proportion to give : — 



Na 2 A1 2 3 Si0 2 Sum 



21-77 35-89 42-34 = 100*00 



Analysis showed 20-50 36-62 42*85 = 99'97 



By heating the intimately mixed oxides at a low temperature 

 (about 800°C) in an electric furnace, grinding and reheating 

 four times, it was found possible to cause the oxides to com- 

 bine without loss of soda. The whole could then be melted to 

 a glass which gave on slow cooling a perfectly homogeneous 

 crystalline mass with no excess of alumina.* 



Even after combination some alumina develops in the per- 

 fectly homogeneous mass if held near its melting point for 

 several days, from which it appears that some soda may still be 

 lost after long heating. No very definite statements can be 

 made concerning this phenomenon inasmuch as every effort 

 was concentrated on its avoidance. 



Preliminary Stitdy. 



A stock of the pure end members being ready, intermediate 

 mixtures corresponding to each 10 per cent interval were 

 made up. 



* The loss of soda gave, of course, an excess in both silica and alumina. 

 The silica undoubtedly went to form a small quantity of a more highly sili- 

 cated compound, probably albite, which, however, did not appear as such 

 and, therefore, must have disappeared in solid solutiorj. Apparently no 



compound in which the ratio, 2 J |, is greater than unity could form under 



the existing conditions and the alumina was left free. 



