THE DISACCHARIDES. 



1. CH 2 OH[CH(OH)] 3 CH(OH)COH + H 2 



(dextro.se) (pfienylhydrazine) 



CH,OH[CH(OH)]..CH(OH)CH 



II +H 2 



N-NH(C,H 6 ) 



(hydrazone) (water) 



2. CH 2 OHrCH(OH)]oCH(OH)CH 



|| +C 6 H 5 .NH-NH 



(hydrazone) (phenylhydrazine) 



CHoOH[CH(OH)] 3 C CH 



|| || +H 2 +H 2 



C 6 H 5 .NH-N N NH.C 6 H 6 



(osazone) (hydrogen) (water) 



The hydrogen seen in the second equation is not really set free, but 

 it is used to split up a further molecule of phenylhydrazine into aniline and 

 ammonia (NH 2 NH.C 6 H- + H 2 = NH 2 C 6 H 5 + NH 3 ). 



In order to obtain the sugar from the osazone again, it is first 

 treated with fuming hydrochloric acid. 1 This gives rise to phenylhy- 

 drazine and a so-called osone. An osone is a substance which, besides 

 the ketone group, contains an aldehyde group as well : CH 2 OH (CH.OH) 3 

 -CO COH. 



By means of zinc and acetic acid the osone is easily reduced to sugar. 



Glucosamine. A derivative of glucose which is of some physiological 

 interest is amido-glucose or glucosamine, C 6 H 11 O f) .NH 2 . This is obtained on 

 the decomposition of chitin and chondroitin. By treatment with nitrous acid 

 it passes into dextrose 



C 6 H U 5 .NH 2 + NOOH *= C 6 H 12 6 + N 2 + H 2 



Glucosamine can also be obtained by treating phenylglucosazone directly with 

 reducing agents 



C 6 H 10 4 . (K 2 H.C 6 H 5 ) 2 + H,0 + H s = C c H n 5 .NH 2 + 



(phenylglucosazone) (glucosamine) 



NH 2 NH.C Q H 6 + NH ? C 6 H 6 



(phenylhydrazine) (aniline) 



This shows us another way of regenerating the sugars from their osazones. 2 

 Further particulars about glucosamine will be found in connection with chitin 

 and cartilage. 



The disaccharides. A disaccharide is a condensation product of 

 two molecules of the simple sugars or monosaccharides, the change being 

 attended with the loss of a molecule of water : 



C 6 H 12 6 + C 6 H 12 6 - C 12 H 22 O n + H 2 

 Thus 



Cane-sugar is derivable from dextrose and levulose ; 

 Milk-sugar, or lactose, from dextrose and galactose ; 

 Maltose, from dextrose and dextrose. 



The general properties of these sugars are like those of the monosac- 



1 E. Fischer, Ber. d. deutsch. cliem. Gesellsch,, Berlin, 1888, Bd. xxi. S. 2631; 1889, 

 Bd. xxii. S. 87 ; 1890, Bd. xxiii. S. 2118. 



2 E. Fischer, ibid., Berlin, Bd. xix. S. 1920 ; Fischer and J. Tafel, ibid., Bd. 

 xx. S. 2569. 



