364 BOARD OF AGRICULTUEE. 



phosphates of a varying composition and of a different com- 

 mercial value. Coarsely ground mineral phosphates, in their 

 natural state, are almost worthless in a commercial fertilizer. 

 As undecomposed bones yield in a much larger degree to the 

 dissolving influence of the carbonic acid in the soil, we prefer 

 superphosphates made from bones to those manufactured from 

 mineral phosphates, in case both contain a larger percentage 

 of insoluble phosphoric acid. To charge the same price for 

 the latter, without reference to the first cost of the crude 

 material, may be profitable to some manufacturers, but cannot 

 be considered fair dealing toward the farmer. The best pro- 

 tection in such cases is to refuse buying those superphosphates 

 which contain more than two per cent, of insoluble phosphoric 

 acid. 



The so-called ammoniated superphosphates receive only in 

 exceptional cases their nitrogen in the form of ammonia com- 

 pounds. In the majority of cases the nitrogen is added in the 

 form of some nitrogenous animal matter, — as ground bones, 

 guano, fish pulp, meat scraps, blood, refuse material from 

 glue-factories, hair, horn, ground leather, etc. Also, Chili 

 saltpetre and potash saltpetre, furnish sometimes the nitrogen 

 iu commercial manures. 



Agricultural chemists distinguish very properly between 

 actual and potential ammonia. The latter refers to the am- 

 monia, which, in the course of time will result from the 

 decomposition of the nitrogen containing organic matter. In 

 some instances this happens very rapidly ; in others it requires 

 months and even years to bring out the full amount of nitro- 

 gen for action. 



Our dealers in fertilizers have not yet been seriously asked 

 to recognize the great difference which exists between the 

 value of nitrogen in the form of ammonia compounds, guano, 

 meat, fish, blood, etc., and in that of hair, horn, woollen 

 refuse, leather scraps, etc. , although in the form of the latter, 

 it is scarcely worth one-half the amount of the former. 



A few subsequent analytical statements may illustrate in a 

 general way, what kinds of superphosphates and ammoniated 

 superphosphates we are bu}ing, and what they are worth, 

 according to our commercial standard retail price. 



