618 



NEW YOEK STATE MUSEUM 



Action of heat on mixture of silica°and bases 



Aluminum sili- 

 cate 



^ 



r4A]A,3Si02 

 2A]203,3Si02 

 Al203,3Si02 



2Al203,9Si02 



r 2FeA3Si02 



Ferric silicate -< 



^re203,3Si02 

 r^FeCSiOo 



Ferrous sili- 

 cates 



2FeO,Si02 



FeO,Si02 

 2FeO,3Si02 



Double or mul- 

 tiple silicates 



I 

 I 



I 



Fe203,Al203,3Si02 



■Fe203,Al203,6Si02 



3FeO,Al203,3Si03 



Agglomerated 

 Agglomerated 

 Strongly agglomerated, 



compact ; fracture stony, 



dull 

 Compact, stony fracture, 



slightly shining 



The mixtures did not de- 

 crease in volume ; there 

 was no combination, the 

 buttons were tenacious of 

 a deep gray color and 

 magnetic. It is now 

 known that silicate of 

 protoxid of iron is formed 

 with the evolution of 

 oxygen. 



Bubbly, finely granular in 

 one part, crystalline in 

 another 



Yery easily melted. Deep 

 olive green 



Melted into compact mass 



Melted into compact, homo- 

 geneous mass 



Apparently was only in 



pasty state 

 Completely melted into 



brilliant black glass 

 Melted into compact mass 



free from bubbles 



From, these results Berthier drew the following conclusions: 



IsTo silicate of alumina is completely fusible at the highest tem- 

 peratures attainable in the furnace (that is such as were in use when 

 Berthier wrote). 



Protoxid of iron produces a remarkably fusible silicate. 



The fusibility of multiple silicates is greater than that of the 

 mean of the component silicates. 



