MANUFACTURE OF PHOSPHORIC ACID. 
15 
The figures given in Table 2 show a volatilization fully as good as 
that obtained where high-grade phosphate rock was used, either at 
Hoboken. X. J., or in the preliminary experiments conducted in this 
same furnace. Xo data, however, were collected in this latter experi- 
ment that would admit of a comparison between the power consumed 
on the mine-run samples and that required for a charge made up of 
high-grade phosphate rock, sand, and coke, but it seems unlikely that 
there would be much difference in these figures since the extra power 
required to smelt the slight increase in the quantity of charge, due to 
the presence of iron and aluminum oxides and perhaps a little extra 
carbonate of lime, should be more than offset by the lowering of the 
melting point caused by the presence of these impurities. In the 
following tables are given the estimated costs of producing the unit 
of P 2 0- by the two processes, namely, the sulphuric acid method and 
the furnace process, from various grades and types of phosphate rock 
in the form of phosphoric acid, acid phosphate, and double super- 
phosphate. 
Table 3. — Estimated cost (at the mines) of producing 1 ton of available -phosphoric acid 
(P 2 5 ) by treating high-grade washed phosphate rock with sulphuric acid. 
Florida hard-rock 
phosphate. 
Florida pebble 
phosphate. 
Tennessee brown- 
rock phosphate. 
Item. 
Quan- 
tity. 
Cost 
per 
Tons. 
Phosphate rock 3.18 I $3.50 
Sulphuric acid (50° B.) ' 3. 44 i 8. 00 
Labor and repairs 2 1. 30 
Total cost per ton of Pa0 5 -- 
Total cost per unit of P2O5. 
Total 
cost- 
$11.13 
27.52 
8.61 
Quan- 
tity. 
Tons. 
3.18 
3.44 
Cost 
per 
ton. 
Total 
cost. 
S2.50 S7.95 
18.00 27.52 
n.30 8.61 
47.26 44.0S 
.47 44 
Quan- 
tity. 
Cost 
per 
ton. 
Total 
cost 
Tons. 
3.18 $2.75 I $8.75 
3.44 J 8.00 27.52 
U.30 8.61 
44.88 
.45 
- Cost per ton, including interest, ta^es, and insurance. 
> Cost per ton of material handled. 
Table 4. — Estimated cost (at the mines) of producing 1 ton of phosphoric acid (P 2 5 ) by 
the electric furnace method from high-grade washed phosphate rock. 
Florida hard-rock Florida pebble 
phosphate. phosphate. 
Tennessee brown- 
rock phosphate. 
Item. 
Quan- Cost Tota , 
tity. ££ cost. 
Quan- 
tity. 
nef Total 
Fan. cost - 
Quan- Cost Total 
tity. P e D r cost. 
Phosphate rock 
Tons. 
3.32 $3.50 111. 62 
1.50 .25 .37 
. 75 8. 00 6. 00 
Tons. 
3.32 $2.50 $8.30 
1.50 .25 .37 
.75 8. 00 6. 00 
Tons. 
3.32 $2.75 $9.13 
Sand 
1.50 .50 .75 
Coke 
. 75 4. 50 3- 37 
Operating expenses: 
Electrodes S2. 13 
1 
50.59 
50. 59 
I 5(1.59 
Power 1 44. 01 
J 
! 1 
68.58 
65.26 
63. 84 
.65 
64 
1 Power at $25 per horsepower year. 
