92 PRACTICAL FARM CHEMISTRY. 



named as source of organic nitrogen in their goods. 

 Phosphoric acid soluble in ammonium citrate is the 

 so-called ^'reverted " phosphoric acid. It belongs 

 to the " available " class, in so far as plants readily 

 assimilate it, and we concede to it a value of eight 

 cents per pound, same as to phosphoric acid solu- 

 ble in water. Some stations, notably those of Mass- 

 achusetts, Connecticut and Pennsylvania, only 

 consider it worth seven and half cents. The insolu- 

 ble phosphoric acid is valued only at two cents a 

 pound, and I think this is all it deserves, although 

 some stations figure it at three cents or more, in the 

 assumption that it is from bone or similar sources, 

 and worth more than that from rock phosphate. 



The small percentage of chlorine shows the 

 potash source to be sulphate, worth five and one- 

 half cents per pound. The peach tree fertilizer 

 made by the same firm has 4.27 per cent chlorine. 

 Here we have the potash evidently in the muriate 

 form, and for this reason would value it only at 

 four and one-half cents per pound. Chlorine makes 

 the application of excessive doses of muriate 

 (chloride) of potash risky for many crops. Its 

 absence shows that a manure has derived its supply 

 of potash from sources other than muriate; for 

 instance, from sulphate, nitrate, or carbonate of 

 j)otash. 



The analyses of fertilizers published in the station 

 bulletins are not all arranged exactly like those of 

 the New Jersey station. At any rate, however, 

 they give us a clue to the computation of the approx- 

 imate values of such fertilizers. 



