FERTILIZERS. 535 



pound, and the gross result is the scientific valuation per ton. 

 Physical condition, and original sources of the materials, are 

 left out of account ; and yet these very considerations affect the 

 value of the fertilizers to an extent often greater than the facts 

 disclosed by the analysis. Upon this basis rests much legislation 

 in behalf of the farmer. 



The chemist makes an arbitrary distinction between three 

 forms of phosphoric acid ; viz. : soluble, insoluble, and what he 

 calls "reverted," for which distinctions the chemist has, of 

 course, his fee. In some cases, and by the laws of some States, 

 the insoluble acid is classed with sand and water, as valueless 

 material. On this point it is only necessary to remark that, 

 under that law, raw ground bones contain nothing of value, 

 except 80 pounds of nitrogen per ton, and would be valued at 

 about $14 per ton; the iioo pounds per ton of phosphate of 

 lime which bones contain being classed under the law with 

 sand and water, as valueless material. In one State, Georgia, 

 the law is, or was, that any goods containing no soluble phos- 

 phoric acid, offered for sale in the State, shall be confiscated ; 

 so that a man offering to sell to the farmers of that State prob- 

 ably the best and most honest fertilizer for the money now to 

 be found in the market, is made a law-breaker and a criminal, 

 subject to pains and penalties. Or else, if an exception is made 

 of the insoluble phosphoric acid in raw bone, the law is self- 

 contradictory, and the state stultifies itself. The law and the 

 State of North Carolina are obnoxious to the same criticism. 



Phosphoric acid, combined with three equivalents of lime, 

 commonly called tri-calcic phosphate, is the sort styled insolu- 

 ble, and said to be " invaluable " to plants. When this tricalcic 

 phosphate is treated with sulphuric acid, a portion of the lime 

 leaves its combination with the phosphoric acid, and forms, with 

 the sulphuric acid, sulphate of lime. The remaining biphos- 

 phate of lime is soluble in water, and this yields the so-called 

 soluble phosphoric acid of the chemist. But what is reverted 

 phosphoric acid ? No man is able to say what it is. It is 

 a chemical nonentity. If a sample of commercial manure is 

 treated with pure cold water, the soluble phosphoric acid is 

 removed. If the residue be treated with a solution of ammo- 

 nium citrate, an additional quantity of the phosphoric acid will 



