42 The Feeding of Anwials 



shown, but they are united to form salts, and so we 

 have the chlorides, sulfates, phosphates, and carbon- 

 ates of potassium, sodium, calcium and magnesium. 

 These are nearly all familiar objects in common life, 

 as, for instance, sodium chloride (common salt), potas- 

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

 potassium sulfate (the sulfate of potash of the market), 

 calcium sulfate (of which gypsum or land plaster is 

 composed), calcium phosphate (burned bone is chiefly 

 this compound), potassium phosphate (a compound of 

 phosphoric acid and potash found chiefly at the drug- 

 gist's) and calcium carbonate (limestone). It should be 

 remembered that the compounds in the ash are not 

 necessarily those of the plant or animal. During the 

 process of ignition, there is a rearrangement of the 

 acids and bases, so that phosphoric acid wdiich was 

 combined with potash in the plant may be united 

 with lime in the ash. Much of the lime in the ash 

 is in union w4th carbonic acid, which in the plant 

 may have been associated w^ith vegetable acids, such 

 as oxalic and tartaric, and part of the sulfur and 

 pliosphorus of the ash comes from the nitrogen com- 

 pounds. 



These salts 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 phos- 

 phates of calcium and magnesium are insoluble in 

 water, but soluble in various acids. These facts are 

 important in showing w^hat salts are in solution in the 

 plant and animal juices, and what effect leaching with 



