44 BULLETIN 1179, U. S. DEPARTMENT OF AGRICULTURE. 
enth tap), but at the end of this time it was observed that the slag 
was growing more viscous and upon examination it was found that 
the oil burners were clogged and no longer properly atomizing the 
fuel. These burners were therefore removed and the small strainers 
contained therein found to be almost entirely stopped by some sedi- 
ment. This shutdown entailed considerable loss of temperature 
which was not regained until 3.45 p. m., when the cinder notches 
w^ere again opened and the furnace tapped freely. The average 
P 2 5 content of this slag (seventh and eighth tap) was 4.24 per cent, 
showing a volatilization of 79.4 per cent. Taking the seventh tap 
(namely, that made at 12.15 p. m.) as indicative of what would have 
been obtained had the burners not become clogged 49 the evolution of 
P 2 5 appears fairly efficient. While the actual figures show a yield 
of only 1.16 pounds of P 2 5 per gallon of fuel oil, the conditions under 
which the furnace was being operated (namely, an empty shaft, no 
heat regenerative effect, and a relatively high oil pressure) were such 
that fully three-fourths of the heat value of the oil was lost during 
the last two hours of operation. 
At 5 p. m. the furnace was again charged with a relatively small 
amount of coke and 550 pounds of briquets. This charge, however, 
went through to the hearth almost immediately so at 9.30 it was 
tapped and this slag (ninth tap) showed a P 2 5 content of 4.4 per 
cent or a volatilization of 78.5 per cent. At 10 p. m. the furnace 
was recharged with 150 pounds of coke upon which between the 
hours of 10 and 11 p. m. 700 pounds of briquets were charged. 
Batches of 100 pounds were continued at 10-minute intervals up 
until 11.40 p. m., when a total of 1,000 pounds had been added. At 
this time the furnace scaffolded somewhat, which was followed by 
channeling, and the oil pressure was accordingly reduced to 50 pounds. 
At midnight this pressure was taken down to 40 pounds (a consump- 
tion of 15 gallons per hour), since it was apparent that the amount 
of oil which was being delivered was in excess of that which could 
be efficiently burned in the furnace crucible. The top of the furnace 
had to be opened from time to time, since the furnace shaft was 
emptied at about midnight and this caused the flames to play directly 
on the furnace top, overheating it at times and also causing the 
stove valves to become dangerously hot. This heat was contin- 
ued, the oil pressure being maintained at 40 pounds for the rest of the 
run. The tapping was begun at 2 a.m., the stoves only being changed 
once between 10.30 p. m. and 2. 30 a. m. and therefore the temperature 
of the air to burners during this period was less than 75° C. The in- 
troduction of a fresh stove at 2.30. hovvever, raised this temperature 
to 175° C. The furnace was tapped clean, and closed down at 6 a. m. 
This slag (tenth tap) showed a P 2 5 content of 4.89 per cent, or a 
volatilization of 76 per cent P 2 5 , giving a yield of 1.29 pounds of 
P 2 5 per gallon of fuel oil. Since the top of the furnace was open, 
however, a large part of the time before the furnace was tapped, the 
bulk of the heat energy of the oil was lost. Only a portion of the 
P 2 5 was transmitted to the electrical precipitator, but approximately 
8 gallons of 45 per cent phosphoric acid was collected toward the 
last of this run. 
< 9 While the seventh and eighth taps were analyzed together, the character of the seventh tap indi- 
cated a high voltilization of P2O5 
