Calcium Metasilicate. 95 



the furnace, but the average difference of temperature between 

 the two elements measures the rate at which heat is passing 

 into the crucible, and any change in this difference shows an 

 absorption or evolution of heat, provided that no great change 

 in the average rate of heating has occurred. 



Inversion of Wollastonite. 

 Rate of heating in 

 degrees per minute. Inversion temperature. 



8-8 1232 



3-6 1225 (See curve 1, Table I.) 



1-0 1198 



1-1* 1197 (See Table II.) Mixed with 



inverted form. 

 1*0 1211 Mixed with inverted form. 



These results indicate, in harmony with the microscopic evi- 

 dence, that the presence of the inverted form has, under the 

 given conditions, little or no effect on the inversion. That the 

 inversion temperature should seem to be higher as the rate of 

 heating increases, was to be expected. The last sample was 

 carried as far as 1245°, and on cooling was found to be 

 inverted only in part. 



The Reversion of Pseuclo- Wollastonite. — When pure pseudo- 

 wollastonite was cooled, even very slowly, it did not revert to 

 wollastonite. Our first efforts to overcome this inertia were 

 along the usual lines. We added to the mass a small quantity 

 of the more stable phase (wollastonite) and allowed plenty of 

 time for equilibrium to assert itself. The two forms, mixed in 

 about equal proportions, were spread in a thin layer at the 

 bottom of a platinum crucible, and on this was placed a 

 deeper layer of the pseudo-wollastonite. Experiments lasting 

 from 36 to nearly 60 hours at temperatures ranging from 900° 

 to 1100° were without effect ; the optical method of identifica- 

 tion always showed both substances and indicated no change 

 whatever. We next tried the effect of the solvent action of 

 water. The two forms, mixed as we have described above, 

 were heated for several days in a steel bomb with water 

 above its critical temperature. The bomb held tight, but 

 there was no indication of change in the crystals. We will 

 not therefore describe the apparatus and the conditions of 

 experiment in detail. Both crystalline forms were proved by 

 the microscope to be practically unchanged by this treatment, 

 and chemical tests showed little hydrolysis. This is some- 

 what surprising in view of the fact that these silicates impart 

 an alkaline reaction to water on standing in the cold. It 

 should be remarked that the quantity of water used was very 

 small, only 3 to 4 cc. to 2 gr. of substance. On the glass 



