532 CONSIDERATION OF CARBON COMPOUNDS. 



compounds of these metals are heated with it in the presence of 

 caustic alkalies. 



3. By easily fermenting when yeast is added to the solution, alco- 

 hol and carbon dioxide being formed : 



C 6 H 12 6 = 2C 2 H 5 OH + 2C0 2 . 



4. By forming with an excess of phenyl-hydrazine, in a solution 

 acidified with acetic acid, a yellow crystalline precipitate of phenyl- 

 dextrosazone. 



Levulose, Fructose, C 6 H 12 O 6 (Fruit-sugar), occurs with glucose in 

 sweet fruits and honey ; it resembles glucose in most chemical and 

 physical properties, but does not crystallize from an aqueous solution ; 

 it may, however, be obtained in white silky needles from an alcoholic 

 solution ; it is met with generally as a thick syrup, is about as sweet 

 as cane-sugar, and turns the plane of polarized light to the left ; it is 

 formed by the action of dilute mineral acids or ferments on cane- 

 sugar, which latter takes up water and breaks up thus : 



C ]2 H 22 O n + H 2 = C 6 H I2 6 + C 6 H 12 6 . 

 Cane-sugar. Dextrose. Fructose. 



Levulose has been made by the polymerization of formic aldehyde, 

 CH 2 O, and also by several other reactions. 



Mannose, C 6 H 12 O 6 . Obtained by the oxidation of mannite ; it does 

 not crystallize and resembles grape-sugar. 



Galactose, C 6 H 12 O 6 , is formed together with dextrose when either 

 milk-sugar or gum-arabic is boiled with dilute sulphuric acid. Galac- 

 tose crystallizes, reduces an alkaline copper solution, but does not fer- 

 ment with yeast. 



When oxidized by heating with nitric acid, galactose forms galactonic add 

 and mucic acids, which are isomeric with the above-mentioned gluconic and 

 saccharic acids. Mucic acid is easily distinguished from saccharic acid by 

 being almost insoluble in water. 



Inosite, C 6 H 12 O 6 (Muscle-sugar). This compound was classed with 

 the carbohydrates on account of its sweet taste; its readiness to 

 undergo lactic and butyric fermentation; and the identity of its 

 molecular formula with that of the hexoses. It has, however, been 

 shown that inosite has an entirely different constitution, being a benzol 

 derivative, viz., hexahydroxy-benzol, C 6 H 6 (OH) 6 . 



Inosite occurs somewhat abundantly in unripe beans and peas, and 

 sparingly in the liquid of muscular tissue ; traces are found in urine, 

 the quantity increasing in certain diseases. It does not ferment with 

 yeast, does not reduce alkaline copper solution, and is optically in-- 

 active. 



