134 CHEMISTRY OF FARM PRACTICE 



the carbonate form, although some chloride and sulphate 

 are present. In the wool of British sheep there is about 



10 per cent of potash salts. Wool is, also, very resistant 

 to nitrification. 



(h) Bone. Raw and steamed bone have been discussed 

 under sources of phosphorus. 



98. Vegetable Sources, (a) Cottonseed meal is the most 

 important source of nitrogen of vegetable origin. It is 

 very highly prized as a feed for animals on account of its 

 high protein content, and can be used to greater advantage 

 as a feed than as a fertilizer, provided that the manure 

 is carefully conserved. It is much used in mixed fer- 

 tilizers, not only on account of the plant food that it con- 

 tains, but on account of the fact that it is an excellent 

 material to keep moisture from salts which might absorb 

 it. Cottonseed meal contains about 2 per cent of avail- 

 able phosphoric acid, 6 per cent of nitrogen, and 1| per 

 cent of water-soluble potash. 



(6) Rape meal is sometimes used as a fertilizer. It 

 contains about 5 per cent of nitrogen and IT^ per cent 

 of phosphoric acid. This meal is the product left after 

 the removal of the oil from rape seed. It is finely ground 

 before being marketed. 



(c) Linseed meal is a by-product of the manufacture of 



011 from flaxseed. The old process linseed meal is the 

 residue left after pressing the oil out of the crushed flax- 

 seed, either when cold or when warm. The linseed meal 

 manufactured by the new process consists of the residue 

 left after extracting the oil with naphtha. Linseed meal 

 obtained by either process contains about 5j per cent of 

 nitrogen, !& per cent of phosphoric acid, and 1| per cent 

 potash. Linseed meal is mainly used as a feed for cattle. 



(d) Castor pomace is the residue left from the extraction 

 of castor oil from the castor bean. It cannot be used as 

 a stock feed on account of poisonous properties; but it 

 has value as a fertilizer. It contains about 5| per cent 



