84 



journal of Agriculture. 



[8 Feb., 1907. 



in fact, belong to a different chemical category. None of them ferment with 

 yeast, and it is very doubtful whether thev can be utilized to any great 

 extent as food. In the human being, though they can be absorbed from 

 ihe bowel, they pass through the body unchanged. Arabinose, prepared 

 from gum arable, and Xylose, prepared from wood, are the two pentoses 

 best known. 



DISACCHARIDES. — These compound sugars are, as has been stated, 

 each composed of two simple sugars united chemically together. When 

 boiled with acids they split up into their two components. Disacchafides 

 aie all white, crystalline, sweet to the taste, and soluble in water. 



I. Saccharose, called also cane sugar or beet sugar. This familiar 

 sugar of commerce is found widely distributed in the vegetable world, as, 

 for instance, in tlie nectar of flowers, in maize, in sorghum, but particularly 



{a) Wheat. 



starch grains (after vogl). 

 {b) Rye. {c) Barley, {d) Oats, (t^ Rice. 





(/J Maize. 



in the sugar cane and sugar beet. With yeast it ferments readily, but it 

 does not give the copper sulphate test. When boiled with an acid it splits 

 into its two components, namely, dextrose and levulose ; this mixture is 

 known as invert sugar, and is frequently used to adulterate honey which 

 it closely resembles in chemical composition. Invert sugar gives, of cO'Urse, 

 the copper sulphate test as the two sugars, dextrose and levulose, are free 

 and not combined chemically. 



2. Maltose. — This disaccharide when boiled with an acid gives only 

 dextrose, but it can be shown that each unit, or molecule, of maltose is 

 composed of two dextrose units, or molecules, united together. It is found 

 in germinating seeds, and thus is present in malt from which it derives its 



