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 Fehling's 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 — 
( "ane-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 intestine must he 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 lie 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 (a) D = +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 : 1 >ut its rotatory power decreases with concentration 
(relatively) and with rise of temperature. 
For a 20 per cent, solution at 15° G. («) 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 Sclieibler, see Tollen's "Handbuch." 
2 Brown, Morris, and Millar (Proc. Cliem. Soc, London, 18P6, p. 244) give («)d= +138°. 
