Minerals of the Composition MgSiO z . 



407 



the cooling is less rapid and the monoclinic pyroxene and ensta- 

 tite are more likely to form. In the above way we succeeded 

 in one instance in crystallizing 27 grams of the silicate entirely 

 to amphibole. Ordinarily, however, a charge of this weight 

 cannot be cooled with sufficient rapidity to prevent crystalliza- 

 tion of more stable forms. 



Our observations appear to have established the fact that 

 the amphibole is more likely to crystallize from the melt if the 

 initial temperature is much above the melting point. The 

 experiments were made in a Fletcher furnace and tempera- 

 tures were roughly measured by means of a thermoelement 

 placed under the hood where the combustion gases emerge. 

 Only rough relative measurements were necessary. The varia- 

 tion in the crystalline product with the initial temperature to 

 which the charge is heated before cooling, is given in the fol- 

 lowing table : 



Table VI. 



Influence of the Initial Temperature of the Liquid on the Product of 

 Crystallization. 

 Temperature in 

 the top of the 

 Fletcher furnace. 



1430° 



1470 



1470 



1480 



14S5 



J490 



1500 



1500 



1500 



Charge. 



Product obtained. 



6 gr. 



Silicate not melted. 



50 " 



Just begins to melt. 



18 " 



Charge had just begun to melt 



6 " 



Amphibole. 



6 " 



Monoclinic pyroxene. 



6 " 



a a 



1510 ( 



27 



50 



8 



6 



8 



12 



" Amphibole. 



" Monoclinic pyroxene. 



" Amphibole. 



a a 



u a 



" Delay in removing the cover 



about three-fourths amphi- 

 bole; one-fourth monoclinic. 

 Amphibole and a little glass. 

 Amphibole. 



(t u 



" Amphibole and a little glass. 



" Amphibole. 



Tollens* found that the unstable form of monochloracetic 

 acid crystallized with greater certainty if the liquid was first 

 * Tollens, Chem. Ber., xvii, i, 664, 1884. 



1500 

 1510 

 1520 

 1525 

 1530 

 1530 

 1530 



1530 

 1535 

 1535 

 1540 

 1545 



12 

 12 



