16 
BULLETIN 1179, U. S. DEPARTMENT OF AGRICULTURE. 
Table 5. — Estimated cost (at the mines) of producing 1 ton of available 'phosphoric 
acid (P 2 5 ) in the form of double superphosphate by treating high-grade washed phos- 
phate rock ivith phosphoric acid obtained by volatilization in the electric furnace . 
Item. 
Phosphate rock 
P20i in form of 58° B. acid 
Labor and power 
Drying 
Total cost per ton of P2O5 . 
Total cost per unit of P2O5. 
Florida hard-rock 
phosphate. 
Quan- 
tity. 
Cost 
per 
ton. 
Tons. 
0.98 
i.67 
$3.50 
68.58 
21.30 
2.25 
Total 
cost. 
$3.43 
45.95 
2.68 
.52 
Florida pebble 
phosphate. 
Tennessee brown- 
rook phosphate. 
Quan- 
tity. 
Tons. 
0.98 
1.67 
Cost 
per 
ton. 
Total Quan- 
cost. tity. 
$2.50 
65.26 
2 1.30 
2.25 
$2.45 
43.72 
2.68 
.52 
Tons. 
0.98 
i.67 
52.58 49.37 
.53 .49 
Cost 
per 
$2. 75 
63.84 
21.30 
2.25 
Total 
cost. 
$2.69 
42.77 
2.68 
.52 
48. 66 
.49 
1 Equivalent to 1 .08 tons of H3PO4 (58° B.). 2 cost per ton of material handled. 
Table 6. — Estimated cost (at the mines) of producing 1 ton oj phosphoric acid (P 2 5 ) 
by the electric furnace method from mine-run phosphates. 
Item. 
Phosphate and matrix 
Washed pebble for reinforcing 
Sand 
Coke 
Operating expenses (electrodes, labor, 
and power). 
Total cost per ton of P2O5 
Total cost per unit of P2O0 
Florida hard rock 
and matrix. 
Florida pebble and 
matrix. 
Quan- 
tity. 
Cost 
per 
ton. 
Tons. 
3.62 
$0.50 
1.64 
.75 
.25 
8.00 
Total Quan- 
cost. tity. 
$1.81 
.41 
6.00 
50.59 
Tons. 
4.89 
1.12 
per* Total 
t P on. 
$0.50 
2.50 
$2.45 
2.80 
Tennessee brown 
phosphate waste. 
Quan- 
tity. 
Cost 
per 
ton. 
Total 
cost. 
Tons. 
3.73 
75 8. 00 ! 6.00 
1.64 
.75 
50.59 . 
58.81 I ! 61.84 
.59 
.62 
SO. 75 $2. 80 
.50 .82 
4.50 3.37 
50. 59 
57.58 
.58 
Table 7. — Estimated cost (at the mines) of producing 1 ton of available phosphoric 
acid (P 2 5 ) in the form of double superphosphate by treating high-grade phosphate rock 
with phosphoric acid from, mine-run material. 
Florida hard-rock 
phosphate. 
Florida pebble 
phosphate. 
Tennessee brown- 
rock phosphate. 
Item. 
Quan- 
tity. 
ne? Total 
" b prist 
ton. C0SU 
• 
Quan- 
tity. 
Cost 
per 
ton. 
Total 
cost. 
Quan- 
tity. 
Cost 
per 
ton. 
Total 
cost. 
Tons. 
0.9S 
i.67 
$3. 50 $3. 43 
58. 81 39. 40 
» i. 30 2. 68 
2. 25 . 52 
Tons. 
0.98 
i.67 
S2.50 
«2. 45 
Tons. 
0.98 
1.67 
?2.75 
57.58 
21.30 
2. 25 
S2. 69 
P2O5 in the form of 5S° B . acid 
Labor and power 
61.84 41.43 
21.30 2.58 
2. 25 . 52 
38.58 
2.68 
.52 
46.03 
47.08 
.47 
44. 47 
Total cost per unit of P"0& 
... .. .46 
.45 
! i 
Equivalent to 1.08 tons of H3PO4 (58° B.). 
2 Cost per ton of material handled. 
While the figures given in the foregoing tables are largely estimates, 
they are considered conservative and fair in so far as the costs of 
each process and type of material used compares with any other. 
Summing up the data given in these tables, we find that the cost of 
the unit of P 2 5 obtained by the electric furnace process on the basis 
of Carothers's figures is considerably higher than the present cost of 
the phosphoric acid produced by the sulphuric acid method, but 
when the phosphoric acid obtained by the former method is used to 
manufacture double acid phosphate, the final cost of the unit of sol- 
uble P 2 5 is brought down very materially. 
When run-of-mine phosphate is treated in the electric furnace, how- 
ever, the cost of the unit of P 2 5 in the form of acid is far below that 
