218 THE CARBOHYDRATES. 



of reducing certain metallic oxides; and the second group, to which the 

 two maltoses and lactose belong, the members acting like monosaccharides 

 in regard to the ordinary reduction tests. The members of the latter 

 group have the character of aldehyde alcohols, and in milk-sugar the 

 aldehyde characteristics are connected with the glucose fraction. 



Saccharose, or CANE-SUGAR, occurs extensively distributed in the plant 

 kingdom. It occurs to the greatest extent in the stalk of the sugar- 

 millet and sugar-cane, the roots of the sugar-beet, the trunks of certain 

 varieties of palms and maples, in carrots, etc. Cane-sugar is of extraor- 

 dinarily great importance as a food and condiment. 



Saccharose forms large, colorless monoclinic crystals. On heating it 

 melts in the neighborhood of 160 C., and on heating more strongly it 

 turns brown, forming so-called caramel. It dissolves very readily in 

 water, and according to SciiEiBLER, 1 100 parts of saturated saccharose 

 solution contain 67 parts of sugar at 20 C. It dissolves with difficulty 

 in strong alcohol. Cane-sugar is strongly dextrorotatory. The specific 

 rotation is only slightly modified by concentration, but is markedly 

 changed by the presence of other inactive substances. The specific 

 xotation is (a) D = +66.5. 



Saccharose acts indifferently toward MOORE'S test and to the ordinary 

 reduction tests. On continuous boiling it may reduce an alkaline copper 

 solution, perhaps on account of a partial hydrolysis. It does not ferment 

 directly, but only after inversion, which can be brought about by an 

 enzyme (invertin) contained in the yeast. An inversion of cane-sugar also 

 takes place in the intestinal canal. Cane-sugar does not combine with 

 hydrazines. Concentrated sulphuric acid blackens cane-sugar very 

 quickly even at the ordinary temperature, and anhydrous oxalic acid does 

 the same on warming on the water-bath. Various products are obtained 

 on the oxidation of cane-sugar, dependent upon the variety of oxidizing 

 agent and also upon the intensity of the action. Saccharic acid and 

 oxalic acid are the most important products. 



The reader is referred to complete text-books on chemistry for the 

 preparation and quantitative estimation of cane-sugar. 



Maltose (MALT-SUGAR) is formed in the hydrolytic cleavage of starch 

 by malt diastase, saliva, and pancreatic juice. It is obtained from glyco- 

 gen under the same conditions (see Chapter VIII). Maltose is also pro- 

 duced transitorily in the action of sulphuric acid on starch. Maltose 

 forms the fermentable sugar of the potato or grain mash, and also of the 

 beerwort. 



Maltose crystallizes with one molecule water of crystallization in fine 

 white needles. It is readily soluble in water, rather easily in alcohol, 



1 See Tollen's Handbuch der Kohlehydrate, 2. Aufl. 1, 124. 



