74 THE CARBOHYDRATES 



Another way of identifying raffinose * is to add to the 

 solution a Uttle decoction of fresh yeast, to act as nutriment, 

 and then to sterih'ze the solution ; a pure culture of top fer- 

 mentation yeast is then added to the solution and the fermen- 

 tation is allowed to proceed in a thermostat at 31"; when it 

 is completed, the solution is boiled with animal charcoal, 

 filtered, and evaporated to a syrup ; the latter is then, while 

 still hot, poured into hot alcohol and on cooling it is filtered ; 

 the filtrate is then precipitated by mixing with 1)7 vols, of 

 ether. After 24 hours the supernatant liquid is poured off 

 and the residual syrup, which consi.sts of melibiose, is con- 

 verted into its osazone which is characterized by its crystalline 

 form and melting point i78-9°f. 



Finally, Neuberg :|: has proposed making use of emulsin for 

 the identification of raffinose. 



MELECITOSE. 

 C,,H,,fl,„ 2H0O. 



This is a sugar which occurs in the sap of Lart'x eiiropaea 

 and in Persian manna ; it crystallizes with two molecules of 

 water in rhombic prisms, and is dextro-rotatory (a^ = + 83°). 

 It does not reduce Fehling's solution, and on hydrolysis yields 

 first a molecule of glucose and a disaccharide — turanose, 

 C^.^H.^Oji — which subsequently itself breaks up into two mole- 

 cules of glucose. 



STACHYOSE. 

 CisH^^Oio, 3H2O or CaeHeoOsi, yH^O. 



This substance may be obtained from the tubers of Stachys 

 tuberifera. It forms plate-like crystals, which dissolve readily 

 in water to give a faintly sweet solution, which is dextro-rota- 

 tory (a„ = + 148°). When boiled with dilute mineral acid it 

 yields glucose, levulose, and galactose.^ 



SUGARS OF UNKNOWN MOLECULAR WEIGHT OR SUGAR-LIKE 

 POLYSACCHARIDES. 



So long as the molecular weight of a sugar is known, it is 

 possible to classify it as a particular kind of saccharide, but 



* Bau : " Chem. Zeit.," 1897, 21, 185. t Ihid., 1902, 26, 69. 



X Neuberg : " Bioch. Zeitsch.," 1907, 3, 519 and 535. 



§ Planta and Schulze : " Ber. deut. chem. Ges.," 1891, 24, 2705. 



