jaeger: melting temperatures of metasilicates 



51 



rapidity with which crystallization proceeds. Actual measure- 

 ments will best illustrate this. In one trial the liquid silicate 

 cooled to 10,914 microvolts where it crystallized suddenly with a 

 rapid rise of temperature to 11,585 microvolts. In a second at- 

 tempt, the charge cooled to 10,857 microvolts, followed by a rise 

 of temperature to 11,650 microvolts. In a third experiment, the 

 thermoelement was moved within the charge at a temperature 

 corresponding to 11,075 microvolts, whereby crystallization was 

 precipitated at once and the temperature rose to 11, 720 microvolts 

 during crystallization. It is therefore clear that the observed 

 temperature of solidification is dependent upon the amount of 

 undercooling and other accidental conditions which chance to 

 surround the charge. It will be noted, furthermore, that the 

 undercooling may amount to more than 1000 microvolts, (approx- 

 imately equivalent to 100°). 



Melting temperatures of lithium silicate 



From these experiments, it again appears clear that solidifying 

 temperatures may have no significance whatever as equilibrium 

 temperatures, but vary with the conditions which chance to sur- 

 round the melt and with its previous treatment. 



This fact probably accounts for the variable results obtained 

 by different observers who have studied the solidifying tempera- 



