262 Cellulose 



(3) Identification of galactose groups by conversion info mucic 

 acid. 1 The substance is oxidised with HNO 3 (1*15 sp.gr.); the 

 mucic acid crystallising out directly, owing to its insolubility. Galac- 

 tose yields 75 p.ct. of its weight of the acid. 



(4) Identification oflevulosegroups by reaction with resorcinoL 

 Levulose may be sometimes identified by the relative ease with 

 which it is converted into levulinic acid. Oxidising methods are 

 not available owing to the ease with which it breaks down into 

 acids of lower molecular weight. The reaction with resorcinol in 

 presence of HC1 a fiery red colouration may be relied on. The 

 reagent is prepared by dissolving 0-5 grm. resorcinol in 60 c.c. 

 HC1 of I '09 sp.gr., with which the solution to be tested is gently 

 warmed. 



(5) Identification of mannose as phenylhydraz one. Mannose is 

 easily distinguished by its property of reacting in neutral dilute 

 solution with phenylhydrazine (acetate) to form an insoluble hydra- 

 /one, which may be further identified by determining its melting 

 point (188). 



(6) Identification of pentaglucoses and oxycelhtlose. These are 

 the furfural-yielding carbohydrates, and their identification and 

 estimation depend upon their conversion into furfural by boiling 

 with HC1 (i'o6). In quantitative determinations the latter is esti- 

 mated as hydrazone. 



Lignocelluloses. Laboratory Notes. It will have been evi- 

 dent to the student that the chemistry of the lignocelluloses is 

 that of a highly reactive molecule, and therefore is different in 

 a great many respects from the celluloses. The reactions of 

 the fibre-substance have also been dwelt upon more in detail 

 than in the case of cotton cellulose, and it will therefore be un- 

 necessary to do more than collect at this point those reasons 

 which are typical and characteristic, and which are useful in the 

 laboratory eitfier for demonstration or in the investigation oi 

 unknown materials. 



(i) Qualitative Reactions. Colour reactions with phloroglucol 

 (solution in HC1), aniline sulphate (aqueous solution) with iodine 

 (absorption with development of brown colour), ferric ferri- 

 cyanide (deep blue dye) with magenta sulphurous acid, and with 



1 The methyl hexoses are similarly oxidised to mucic acid. (E. Fischer, 

 BerL Ber. 1894, 385.) 



