MANUFACTURE OF PHOSPHORIC ACID. 47 
by this method appears economically superior to that which is now 
almost universally employed. 
Probably, if all the factors are considered, the fairest and at the 
same time some of the most favorable figures showing the ratio of oil 
consumed to the yield of product were obtained during the latter part 
of the 20-hour test begun on October 8, 1920. The cost data given 
below therefore are largely based on these results, and while it is 
assumed that the operation be conducted on a larger scale, in a 
furnace with an average daily output of 30 tons of P 2 5 , the fuel con- 
sumption per ton of P 2 5 produced is that actually determined in the 
last three and a half hours of this test with the Arlington furnace. 
In Table 19 is given the estimated cost of mine-run phosphate 
briquetted and ready for furnace treatment, in Table 20 the cost of 
producing 1 ton (2,000 pounds) of P 2 5 from this briquetted charge is 
shown, and in Table 21 the cost of manufacturing available phos- 
phoric acid by treating high-grade washed phosphoric rock with the 
liquid phosphoric acid thus produced is given. 
Table 19. — Quantities and estimated cost of mine-run phosphate and coke braize 
required per ton o/P 2 5 , and cost of briquetting this mixture for furnace treatment. 
charge and its manipulation for furnace treatment. 
Mine-run phosphate and sand. 
Mining 
Drving •*. 
Grinding 
Coke braize 
Grinding 
Mixing and briquetting 
Total 
Quantity. 
Pounds. 
10,542 
10, 542 
10,542 
1,716 
1,716 
12,258 
Cost— 
Per ton of Per ton of 
material. P2O5. 
$0.75 J 
.25 
.25 
5.00 
.50 
1.25 
8.00 
S3. 53 
1.18 
1.18 
4.29 
.40 
7.66 
18.24 
Table 20. — Estimated cost per ton of phosphoric acid (P 2 5 ), 90 per cent yield, produced 
by smelting briquetted charges of mine-run phosphate in an oil-burning furnace . 
Items. 
Cost. 
Items. 
Cost. 
Briquetted material 
$18.24 
7.20 
3.50 
.55 
1.82 
S3. 00 
Fuel oil, 360 gallons, at 2 cents per gallon. . 
Power 
.50 
Overhead expenses 
1.50 
Total cost per ton 
Depreciation on $100,000, at 20 per cent 
36.31 
Total cost per unit 
.36 
Table 21. — Estimated cost 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 obtained by the fuel furnace process. 
Quantity. 
Cost— 
Item. 
Per ton 
of 
material. 
Per ton 
of 
product. 
Phosphate rock (washed) 
Tom. 
0.98 
1 .67 
S3. 50 
36.31 
2 1.30 
2.25 
S3. 43 
P2O5 in form of 58° B. acid 
24.35 
Labor and power 
2.68 
Drying 
.52 
Total cost per ton P2O5 
30.98 
Total cost per unit P2O5 
.31 
1 Equivalent to 1.08 tons of II3PO4 (58° B.). 
2 Cost per ton of material handled. 
