io CHEMICAL CONSTITUENTS OF BODY AND FOOD. 



charides ; their solubilities are similar ; they are optically active, 

 crystallisable, diffusible, and sweet. Heated dry, they give rise to 

 caramel. Further, they (with the exception of cane-sugar) reduce 

 alkaline solutions of metallic oxides like Fehliag'e solution, and (again 

 with the exception of cane-sugar) form crystalline osazones. 



By hydrolysing agencies they take up water, and split into the simple 

 sugars of which they are made up. Thus 



Cane-sugar + water = dextrose + levulose. 

 Maltose + water = dextrose + dextrose. 

 Lactose + water dextrose + galactose. 



Among the agents capable of producing this decomposition the 

 inverting ferment of the small intestiiae must be particularly mentioned. 

 The term inversion arose from the fact that, if cane-sugar is the sub- 

 stance acted on, the previously dextrorotatory solution becomes levo- 

 rotatory, because the levorotatory power of the levulose is greater than 

 the dextrorotatory power of the dextrose formed. The term inversion 

 has, however, been extended to include the similar decompositions of 

 lactose and maltose. The reverse action by which the monosaccharides 

 are united to form disaccharides is called reversion. 



Cane-sugar is generally distributed throughout the vegetable 

 kingdom in the juices of plants and fruits, especially the sugar-cane, 

 beetroot, mallow, and sugar-maple. As a food it is of high value. After 

 abundant ingestion of cane-sugar, traces may be found in the blood and 

 urine ; but the greater part undergoes inversion in the alimentary 

 canal. 



It is readily soluble in water (100 parts of saturated solution contain 

 67 of sugar), 1 but soluble with difficulty in alcohol. It forms large, 

 colourless monoclinic crystals. It is strongly dextrorotatory, and 

 the amount of rotation does not vary so much with concentration 

 and temperature as do most of the other sugars. The average value 

 of (<*)= +66-5. 



Cane-sugar does not give many of the sugar tests ; thus, it does not 

 give Moore's test ; with Trommer's test, it gives a blue solution, but no 

 reduction occurs on heating. It does not react with phenylhydrazine, 

 and it is not directly fermentable by yeast ; the yeast, however, secretes 

 an inverting ferment, and after inversion the glucoses formed are con- 

 verted into alcohol and "carbonic acid. 



By boiling with concentrated hydrochloric acid a deep red solution 

 is formed. Dextrose, maltose, and lactose do not give this reaction. 



Maltose is one of the end products of the action of malt diastase on 

 starch. It is also the chief sugar formed from starch by the diastatic 

 ferments contained in the saliva and pancreatic juice. It is an inter- 

 mediate product in the action of sulphuric acid on starch. It crystallises 

 with one molecule of water of crystallisation in fine white needles. It 

 is easily soluble in water and in alcohol ; insoluble in ether. It is 

 dextrorotatory; but its rotatory power decreases with concentration 

 (relatively) and with rise of temperature. 



For a 20 per cent, solution at 15 C. (a) D = + 139-3. The amount 

 of rotation is about 18 less for a freshly prepared solution than for one 

 which has stood for some hours. 2 



1 Scheibler, see Tollen's "Handbuch." 



2 Brown, Morris, and Millar (Proc. C'hem. Soc., London, 1896, p. 244) give ()D= +138. 



