PART I. CONSTITUENTS OF PLANTS AND 

 ANIMALS 



CHAPTER II 



THE MINERAL SALTS 



Chemical Composition of Ashes. When animal or vegetable 

 matter in its natural state is burned, a large part of it dis- 

 appears in the form of gases, but some solids always remain 

 behind as ashes. The quantity of ash ingredients varies 

 widely in different kinds of organic matter. In the bones of 

 animals it may amount to between 40 and 50 per cent, of the 

 original substance. Chaff, husks, and withered leaves contain 

 from 10 to 20 per cent, or more of ash ingredients. On the 

 other hand, the muscular and fatty tissues of animals, the 

 inner portions of seeds, potato tubers, fleshy roots, etc., contain 

 only a very small proportion rarely more than 2 or 3 per 

 cent, of the dry matter, and in some cases less than i per cent. 

 The ash will usually be found to contain some of all 

 elements originally present in the organic matter z>. those 

 previously mentioned (p. 2) except hydrogen and nitrogen, 

 which are completely volatilised on incineration. The elements 

 are not, of course, present in the ash in the free state, but in 

 combination as oxides, chlorides, and fluorides. The acidic 

 oxides, viz. P 2 O 5 , SO 3 , and CO 2 , are further combined with 

 the basic oxides K 2 O, MgO, and CaO. The silica and oxide 

 of iron are probably, for the most part, uncombined. It may 

 be said that, in general, the ash consists of the 



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