REPORT OF THE CHEMIST. 



75 



ammouium citrate. Its fertilizing- actiou is believed not to be as prompt 

 as is that of soluble pliospliates, still it is far more valuable than insoluble 

 I)liosi)liate. 



3. — Insoliihle phos^pJioric acid. 



Insoluble phospliate of lime (3CaOP205) is not soluble either in water 

 or in ammonium citrate solution. Jts effect upon crops is comparatively 

 slow, and its agricultural value depends upon .the condition in which it 

 exists, since if in bones its value is much greater than in the form of pal 

 verized mineral phosphate. 



SUPERPHOSPHATES. 



Superphosphates are commercial fertilizers in which all or a part of 

 the phosphoric acid has been rendered soluble by treatment with sul- 

 phuric acid. In a recent well-prepared superphosi)hate nearly all the 

 phosphoric acid is in a soluble condition; in practice, however, this is 

 usually not found to be the case. Either by improper methods of man- 

 ufacture or by long keeping part of the i^hosphoric acid becomes "re- 

 verted," and part occurs as " insoluble." Hence, analyses of phosphatic 

 manures, to be of value, should state definitely the amount of each form 

 of phosphoric acid. 



A high-grade superphosphate, which had been very carefully made, 

 contained practically all its phosphoric acid in the soluble form. Anal 

 ysis showed that it amounted to 15,20 per cent. 



The two following analyses show the composition of ordinary samples 

 of superphosphates. 



Anahjries of ferlUlz:rs. 



Const! tuenta. 



No. 1. 



No. 2. 



Moisture, loss by drying at 110° C 



Volatile organic matter 



Sand and clay insoluble in acids 



Oxides of iron and alumina 



Lime, Ca O 



Magnesia, Mg O 



Potash, K»0 



Soda.NaoO 



Ammonia, NH3 (^^ .35 per cent, nitrogen) 



Sulphuric acid, SO3 



Phosphoric acid, soluble 



Phosphoric acid, reverted 



Phosphoric acid, insoliiblo 



Total 



VALUATION OP FERTILIZERS. 



The commercial value of a fertilizer can be approximately deduced 

 from the results of analysis; it is chiefi.y dependent upon the mark et 

 value of the crude materials which are used in its manufacture. The 

 agricultural value of the same fertilizer is a variable quantity, and de- 

 pends to a considerable extent upon the soil to which it is applied, the 

 heat, moisture, and various climatic conditions. The same fertilizer 

 under different circumstances may give good or indifferent results which 

 cannot justly be charged to the fertilizer alone. Under average, nor- 



* Total nitrogen, .58 per cent., equivalent to .70 per cent, ammoni.'t, of which .43 per cent, was actual 

 ana .27 per cent, potential. 

 t Total nitrogen, 2.70 per cent., equivalent to 3,28 per cent, of ammooi.^,, all potential. 

 Nitrates -weTe absent in both fertilizera. 



