76 THE CARBOHYDRATES 



Another way of identifying raffinose * is to add to the 

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

 and then to sterilize 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 i^ vols, of 

 ether. After 24 hours the supernatant liquid is poured off 

 and the residual syrup, which consists of melibiose, is con- 

 verted into its osazone which is characterized by its crystalline 

 form and melting point i78-9°i'. 



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

 the identification of raffinose. 



MELECITOSE. 

 CisHsaOxe, 2H2O. 



This is a sugar which occurs in the sap of Larix europaea 

 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, 

 Cj2H220jj — which subsequently itself breaks up into two mole- 

 cules of glucose. 



STACHYOSE. 

 C1SH32O16, 3H2O or C36H62O31, 7H2O. 



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 (ao = + 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. 



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



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



