MANN1TK. 7^7 



INSIPID SUGAR. 



A species of sugar was obtained by Thenard, from the urine of 

 diabetes insipidus, and subsequently by Bouchardat from the 

 same source, which was insipid, or only faintly sweet. It was 

 fermentable by yeast, and was converted by dilute sulphuric acid 

 into the sugar of grapes.* 



LIQUORICE SUGAR. 



The inspissated juice of the root of the Glycyrrhiza glabra, 

 contains a species of unfermentable sugar, which is obtained by 

 clarifying the juice with albumen, and precipitating the sugar 

 with sulphuric acid, washing the precipitate with water, dissolv- 

 ing it in alcohol, which leaves undissolved some albumen, and 

 then decomposing the sulphate of liquorice sugar by carbonate 

 of potash. After evaporation, the sugar remains as a yellow 

 translucent mass, cracked in all directions, and easily detached 

 from the vessel in which it was evaporated. Liquorice sugar 

 possesses the property of forming soluble or sparingly soluble 

 compounds with both the mineral and vegetable acids. It also 

 combines with bases. 



MANNA SUGAR, OR MANNITE. 



C 6 H 7 O 6 , according to the analyses of Oppermann and of 

 Liebig. Manna is in oblong globules or masses, of a yellowish 

 white colour, and is an exudation from various trees, principally 

 the Fraxinus ornus, a species of ash, and the Eucalyptus manni- 

 fera of New South Wales. It exists also in the juices exuded by 

 many cherry and plum trees, in various kinds of mushrooms, 

 and in some roots, such as that of celery. It is composed 

 chiefly of manna sugar, which may be prepared by dissolving the 

 manna of the shops in boiling alcohol, and allowing the solution 

 to cool, and is obtained perfectly pure by repeated crystalliza- 

 tions. Mannite crystallizes in slender, colourless, four-sided 

 prisms, of a silky lustre. It has a slightly sweet taste, and is 

 very soluble in water ; its solution is not fermentable. Mannite 

 is anhydrous, and may be fused by heat without loss of weight. 



* Thenard, Trate de Chimie, IV. 351. 



