4§ ANNUAL REPORT 
Name of Silicate. Molecular Formula. Oxygen Ratio. 
IVARSMMORMIO. 6b obeb ooo 2RO 3510, Zi Oy —= lees 
IBIESMNOMOs cose4coo50¢ RO SiO, M2 
Sesqui-silicate........ 4RO 3510, 429 3 22 3 
Singulo-silicate....... 2RO SiO, 2 ara elke 
SWUOSMCNUO: 5 oo 5046566 3RO SiO, 3) 8 
We observe that the names of the silicates are derived from the 
Oxygen ratio which has been universally accepted as the metallurgical 
nomenclature. 
According to Ledebur, the bi-silicate of calcium is the most fusible 
compound, the temperature rising with an increase in lime.or silica. The 
singulo and tri-silicates fuse only at a very high temperature, while the 
subsilicate is infusible excepting in the electric furnace and in the oxy- 
hydrogen flame. The magnesium silicates are all difficult to fuse and do 
not show such decided differences in their melting points as the calcium 
silicates. Of the lime-magnesia silicates (one molecule of CaO to one 
molecule of MgQ) the bi-silicate is, according to Berthier, the most 
fusible one, while the tri-silicate is the most infusible. 
The presence of alumina modifies the melting point of a slag consid- 
erably, the most fusible lime-alumina silicate being, according to Bode- 
mann*, a bi-silicate approximately 4CaSiO,+AlI,S1,O0,. Berthier found 
that all lime-alumina silicates are most fusible when the amount of 
alumina is about one-third of that of lime, by weight, it being equal to 
I equivalent of alumina for 6 equivalents of lime or 102 parts by 
weight of alumina to 336 parts of calcium oxide. 
The same investigator found that an increase in the lime content 
causes the melting point to rise only very gradually, but rapidly as soon 
as the alumina is increased, so that silicates with the molecular ratio of I 
equivalent of alumina to 3 equivalents of calcitim oxide are still fusible, 
while with a ratio of 2 alumina to 3 of lime the slags are almost infusible. 
Beside the melting point proper, we must consider the degree of 
liquidity or the viscosity of the slag on melting. The slags melting at the 
lowest temperatures are not always the most liquid ones. The slower 
the transformation from the solid to the liquid condition the more viscous 
and “tough-liquid” will the slag be. Slags high in silica and also those 
high in magnesia or alumina show this property quite strongly and hence 
are as unfit for the purposes of-iron manufacture as slags with too high 
a melting point. In a slag of proper composition the fusion takes place 
—_——— 
*Bodemann, Probirkunst, p. 251. 
