24 BULLETIN 144, U. S. DEPARTMENT OF AGRICULTURE. 
Table VII.— Average cost per ton {2,000 pounds) of acid phosphate manufactured in a 
den-system plant located at seaport and running at full capacity of 500 tons per week.. 
Phosphate rock (1,133 pounds), at $5.09 per ton $2. 576 
Sulphuric acid (1,080 pounds), at $4.75 per ton ." 2. 565 
Direct labor 264 
Five-eighths superintendent's salary 091 
Po^er, oil, and ^aste < . . 232 
Insurance on 860,000, at 1.55 per cent 035 
Taxes on $75,000, at 1.25 per cent 036 
Depreciation on $60,000, at 10 per cent . 231 
Interest on $75,000, at 6 per cent 173 
Total cost per ton 6. 203 
The figures given in Table VII were compiled from data obtained 
through personal inspection of the principal fertilizer factories of 
the South and East. The costs do not include overhead charges, 
which vary greatly according to the size and number of the plants 
run by a company. 
DISPOSAL OF PRODUCT. 
Acid phosphate is sold on the basis of its so-called available phos- 
phoric-acid content, and is worth f. o. b. the factory from 40 to 56 
cents per unit, 1 depending on the location of the plant and grade of 
the product. 
The availability of phosphoric acid is determined by its solubility 
in a solution of ammonium citrate. There seems to be no scientific 
basis for the assumption that the amount of phosphoric acid thus 
dissolved is equivalent to the quantity which is readily available to 
crops. It is, however, a convention accepted by the fertilizer trade 
as well as by many agronomists and agricultural chemists. 
The phosphates of South Carolina (27 per cent P 2 5 ) and those of 
northern Africa (26 to 30 per cent P 2 5 ) yield as a rule acid phosphate 
containing 14 per cent available phosphoric acid. 
Florida land-pebble phosphate gives an acid phosphate containing 
16 per cent of available phosphoric acid, and the highest grade rock 
from Florida, Tennessee, and certain islands in the Pacific Ocean 
(containing from 35 to 38 per cent P 2 5 ) yield a product containing 
from 18 to 21 per cent of available phosphoric acid. 
Acid phosphate is usually put up in 200-pound sacks and shipped 
in closed box cars. The sacks are treated with a solution of silicate 
of soda, paraffin, or some other substance to prevent the acid phos- 
phate from acting upon them. 
The latest official figures on the output of acid phosphate are those 
for 1909, which show a total production of 3,062,834 tons. It is 
needless to say that the production has increased enormously since 
these figures were compiled . 
1 The unit is 1 per cent of a ton, or 20 pounds. One ton of 16 per cent acid phosphate contains 320 
pounds P2O5. 
