36 
BULLETIN 1179, U. S. DEPARTMENT OF AGRICULTURE. 
established where the slag would freeze upon the furnace walls' 
protecting them, from further action by the molten charge. 
I fc£« 
• In the above chart (fig. 11) the rate of volatilization of P 2 0. 
from briquets of various compositions is graphically illustrated by 
curves. 
