8 THE CHEMISTRY OF CATTLE FEEDING 



The ash is therefore said to consist of " mineral salts," and 

 these, in turn, are usually quoted as one of the constituent 

 groups of compounds in the proximate composition of plants 

 and animals. 



The term " mineral salts," however, is a misnomer, and has 

 often proved misleading. The ingredients of the ash are not 

 " mineral." They are just as much organic products as the 

 fats or proteins ; and there is good reason to believe that some 

 of them, e.g. phosphorus, sulphur, etc., exist in the plants and 

 animals, not in the form of salts at all, but, to some extent at 

 least, as constituents of the compounds mentioned. At the 

 same time, it must be kept in view that certain salts, e.g. 

 common salt, are present in that form in the sap of plants and 

 in the blood, urine, and other fluids of animals. 



It is more than probable that the carbonates found in the 

 ashes do not exist in that form in the living plants and animals, 

 but are formed from other compounds in the process of com- 

 bustion. For this reason, many authors regard the presence 

 of carbonates in the ash as merely accidental, and they deduct 

 the amount of carbon dioxide found from the total crude ash 

 and call the residue " pure ash." 



The same argument might be applied to the sulphates. 

 It is tolerably certain that much, if not all, of the sulphates 

 found in the ashes of natural organic substances are formed 

 during the process of combustion by oxidation of the sulphur 

 which, in the original organic matter, formed part of the 

 proteins or other compounds. Fleischman 1 actually does 

 adopt this course in regard to the ash of milk. He deducts 

 the whole of the SO 3 because sulphates are not present in 

 the milk. He also deducts a part of the PO 5 corresponding 



1 "The Book of the Dairy," English translation, p. 27. 



