14 
Table 1. — Analyses of air-dried samples of mine-run and waste material from the 
Florida and Tennessee phosphate fields. 
Constituent. 
Florida 
hard-rock 
and 
matrix. 
Florida 
pebble 
phosphate 
and 
Tennessee 
brown 
phosphate 
waste. 
CO? 
Per cent. 
2.22 
14.37 
30.69 
5.03 
42.07 
3.6S 
Per cent. 
1.53 
45.99 
15.38 
7.50 
22.79 
1.58 
Per cent. 
1.49 
Si0 2 
14.23 
P2O5 
29.85 
A I2O3+ Fe 2 03 
7.72 
CaO 
40.42 
F 
2.71 
Total 
98. 06 
94.77 
96-42 
Since the ratio of lime to silica used in the smelting experiments 
previously described was approximately 1 to 1.44, it will be seen 
from the analyses given in Table 1 that the samples of Florida hard- 
rock phosphate and matrix and Tennessee waste phosphates required 
further additions of sand, but that the mine-run Florida pebble had 
to be reinforced with higher grade phosphate rock in order to produce 
a charge suitable for furnace treatment. Further studies of the 
pebble phosphate deposits of Florida have shown, however, that the 
sample used in this case was probably exceptional, and that most of 
the run-of-mine material will require the addition of silica. In this 
particular instance, however, the mine-run pebble phosphate was 
reenforced with washed pebble rock containing 32 per cent of P 2 5 
and 7 per cent of Si0 2 . The material from Florida hard-rock fields 
and that from the Tennessee dump heaps were mixed with high-grade 
white sand and sufficient coke was added in each instance to bring 
about the necessary reduction in the smelting operation. Approx- 
imately 500 pounds of each charge was made up and smelted in the 
electric furnace for three hours, the phosphoric acid volatilized being 
collected by means of the Cottrell precipitator employed by Ross, 
Carothers, and Merz. Since the charge used was relatively small and 
the duration of the tests comparatively short, no attempt was made 
to determine the quantity of P 2 5 volatilized from the weight of acid 
collected by the precipitator, as there was of course a considerable 
loss in saturating the system. At the end of three hours, however, 
the furnace was tapped and the amount of phosphoric acid (P 2 5 ) 
remaining in the slag was determined by analysis, that which was 
volatilized being figured by difference. The figures showing the 
efficiency of this furnace treatment as applied to mine-run rock are 
given in Table 2. 
Table 2. — Quantity of phosphoric acid (P?0 5 ) volatilized from a charge made wp of 
mine-run phosphates when smelted in the electric furnace for 3 hours. 
Phosphatic material used in charge. 
Hard-rock phosphate and matrix... 
Land-pebble phosphate and matrix 
Tennessee waste material 
P2O5 in 
charge ex- 
clusive of 
coke, CO 2, 
andF. 
Per cent. 
22.0 
19.1 
21.3 
P2O5 in 
slag by 
analysis. 
Proportion 
of total P2O5 
remaining 
in slag after 
smelting. 
P(r cent. 
0.50 
.66 
.67 
Per cent. 
1.8 
3.0 
2.7 
Amount 
of P2O5 
volatilized. 
Per cent. 
98.2 
97.0 
97.3 
