Calcium Metasilicate. 



97 



Curve I. — Inversion of Wollastonite. 



Inversion Temperature, 1225°. 

 Rate of Heating, 3 - 6° per minute. 



11500 



10 20 



Time in Minutes. 



there were signs of some action. The grains were cemented 

 tightly together, while the microscope disclosed what appeared 

 to be an incipient crystallization. 



From water we turned to the solvent action of a fused salt.* 

 The necessary properties in a salt which should answer our 

 purpose are evidently the possession of an ion common to cal- 

 cium silicate, so that metathesis may not result ; sufficient fusi- 

 bility, and sufficient solubility, in order that the excess may be 

 removed after the process is complete. 



These requirements are fulfilled by calcium vanadate, 

 Ca(V0 3 ) 2 , which is prepared by heating calcium carbonate with 

 the proper proportion of vanadic acid. In the first trial, we 

 heated one gram of vanadate with several grams of pseuclo- 

 wollastonite at a temperature of 800° to 900° for a number of 

 days. The solvent was then partially extracted by hot water, 

 after which the residue, so far as possible, was removed by very 

 dilute hydrochloric acid. The product was all changed into 

 wollastonite. In later experiments, we tried larger quantities of 

 vanadate and heated for different periods. One gram of vana- 

 date readily transforms 5 grams of silicate and is removed 

 when the change is accomplished with less trouble than a 



* Calcium chloride forms chloro-silicates. Gorgeu, Bull. Soc. Min., x, 271. 

 In our experiments we did not get a pure product, though the majority of it, 

 when a large excess of calcium chloride was used, crystallized in ti'anspai'ent 

 lath-like crystals of orthorhombic (?) symmetry. The ratio of chlorine to 

 silica in the product was in accord with the formula 2CaSi0 3 .CaCl 2 . 



