62 FERTILIZERS. 



bone over the freight on a purchased ton of the super- 

 phosphate, and a certain fraction of per cent to be allowed 

 on the breakage of carboys, which will occasionally occur 

 in transportation ; and the remainder, plus the advantage 

 of knowing that we have the real article, will be the re- 

 turn for our labor. Let us next see what the home-made 

 phosphoric acid will cost us when the mineral phosphate 

 is used. 



The phosphate rocks of South Carolina supply us with 

 our cheapest source for soluble phosphoric acid. These 

 are richer in phosphate of lime than the deposits of North 

 Carolina, and require half more sulphuric acid to make 

 their phosphoric acid soluble. The cost of soluble phos- 

 phoric acid at the present market price for material, viz., 

 $13 per ton for finely ground phosphate rock, and $28 per 

 ton for oil of vitriol, sixty-six degrees, is as follows : 



1,000 pounds phosphate . . . . . . $6 50 



600 " sulphuric acid . . . .840 



300 " water. 



1,900 " total. 



90 deducting 10 per cent for loss in gas and vapor. 



1,810 pounds, costing $14 90 



At 13 per cent, the soluble acid would be 235 pounds, 

 costing $14.90, or about 6 cents per pound. 



The phosphoric acid in finely ground bone can also be 

 made available by the caustic action of the potash in un- 

 leachedwood ashes. Dr. Nichols recommends the following 

 method : " Take 1 barrel raw bone flour, 3 barrels dry un- 

 leached wood ashes, 90 pounds gypsum, and 10 gallons of 

 water ; make a heap of the solid materials on the barn floor, 

 and add the water, stirring constantly with a hoe. The re- 

 sult is perfect plant-food, containing all the elements plants 



