68 TOBACCO CULTURE. 



Nitrogenous Guanos are formed in dry regions. The 

 Peruvian guano is rich in ammonia, containing 8 per cent, 

 or more. They usually contain 7 to 12 per cent, phosphoric 

 acid, and about i per cent, potash. 



Bones consist mostly of phosphate of lime, which con- 

 stitutes from one-half to three-fifths of the weight of the 

 bone. The remaining portion is a soft, fleshlike substance 

 commonly called gelatin. It is distributed throughout the 

 entire mass of bone, and is rich in nitrogen. When bones 

 are burned, the nitrogenous matter is driven off and only 

 the mineral portion of phosphate of lime remains. Bones, 

 such as arc used in making commercial fertilizers, contain 

 5 to 6 per cent, of ammonia, and from 20 to 25 per cent, of 

 phosphoric acid, about two-thirds of which is insoluble and 

 approximately one-third available. 



Bone Products. All forms of bone products are valu- 

 able fertilizers, as they supply phosphoric ncid, and gener- 

 ally ammonia also. The most common forms are bone 

 black, bone meal and bone tankage. Bone-black is a by- 

 product of sugar refining, and contains from 30 to 35 per 

 cent, phosphoric acid, more than half of which is immedi- 

 ately available. Bone meal is simply ground bones, steamed 

 or raw. It contains 3 to 6 per cent, of ammonia and 20 to 25 

 per cent, of phosphoric acid. Bone tankage is a very irreg- 

 ular product, but follows bone meal closely in composition. 

 It is a by-product of the smaller packing houses. 



Phosphate rock. This is a mineral phosphate, found in 

 various States. In a raw condi'ion it contains from 25 to 



