COMPOUNDS OF NUTRITION 39 



chloride (the muriate of potash of the market), potassium 

 sulfate (the sulfate of potash of the market), calcium sul- 

 fate (of which gypsum or land-plaster is composed), cal- 

 cium phosphate (burned bone is chiefly this compound), 

 potassium phosphate (a compound of phosphoric acid 

 and potash found chiefly at the druggist's), and calcium 

 carbonate (limestone). 



49. Rearrangement of ash elements during ignition. — 

 It should be remembered that the compounds in the ash 

 are not necessarily those of the plant or animal. During 

 the ignition of plant or animal substance, organic com- 

 pounds are broken up, certain acid and basic elements of 

 which enter into other combinations in the salts of the 

 ash. Much of the lime in the ash is in union with carbonic 

 acid, which in the plant may have been associated with 

 vegetable acids, such as oxalic and tartaric, and part of 

 the sulfm- and phosphorus of the ash comes from cer- 

 tain carbon compounds. 



The salts of the ash differ greatly in their properties. 

 Some are soluble in water, others are not. To the former 

 class belong all the chlorides, and the potassium and 

 sodium sulfates and phosphates. The normal phosphates 

 of calcium and magnesium are insoluble in water, but 

 soluble in various acids. These facts are important in 

 showing what salts may be found in the plant and animal 

 juices, and what effect leaching with water or other sol- 

 vents might have on the inorganic portion of cattle foods. 



50. The ash compounds of plants. — Upon incinera- 

 tion, all plants and feeding-stuffs yield an ash residue 

 which has been termed the mineral part of the plant. The 

 ash elements are important in this connection because 

 they are the main source of the same elements of the 

 animal body. These may be held in plant tissue in three 



