The Composition and Use of Fertilizers. 



227 



They are sometimes treated with superheated steam or with sul- 

 phuric acid, the treatment rendering the nitrogen compounds 

 more readily available. 



Leather Scraps and Leather Meal are waste products of various 

 factories. When treated with superheated steam and dried or 

 roasted, they can be very finely ground. Roasted, finely ground 

 leather is used to adulterate dried blood, having much the same 

 appearance. 



Nitrogenous Guanos are formed in warm dry regions. Peru- 

 vian guano is rich in nitrogen, containing seven per cent, or more, 

 mainly in the form of sulphate of ammonia. Guanos of this 

 kind have largely disappeared from the market. 



The following table gives the approximate quantities of nitro- 

 gen contained in various fertilizing materials: 



Materials Containing Nitrogen. 



.„„, „ „„ Pounds of nitro 



Average per . „ noo 



c^t; ° f pounds of 



nitrogen. l mat erial. 



(1) Mineral materials. 



Nitrate of potash 13 to 14 260 to 280 



Nitrate of soda 151 to 10 310 to 320 



Sulphate of ammonia 19 to 20J 380 to 410 



(2) Vegetable materials. 



Cotton seed meal 6 to 7 120 to 140 



Castor bean pomace 5 to 6 100 to 120 



Linseed meal 5 to 6 100 to 120 



Tobacco stems 2 to 2h 40 to 50 



(3) Animal materials. 



Azotin, ammonite 10 to 12 200 to 240 



Dried blood, red 13 to 15 200 to 300 



Dried blood, black 6 to 12 120 to 240 



Dried fish 7 to 8 140 to 160 



Hair _^ 14 to 16 280 to 320 



Hoof meal, horn dust 10 to 15 200 to 300 



Leather scraps, leather meal 7 to 8 140 to 160 



Meat scraps 10 to ] 2 200 to 240 



Nitrogenous guanos 7 to 8 140 to 160 



Oleomargarine refuse 10 to 12 200 to 240 



Tankage*, concentrated 10 to 12 200 to 240 



Tankage, crushed 4 to SO to 180 



Tankage, garbage 1 to 2 20 to 40 



Wool waste 5 to 100 to 120 



(b) Fertilizing Materials Containing Phosphoric Acid Compounds. 



Phosphoric acid is generally found in combination with lime 

 (calcium), forming four different compounds, viz.: 



(1) Insoluble phosphate of lime, or tri-calcium phosphate. 



(2) Soluble phosphate of lime, or mono-calcium phosphate. 



