Experimental and Applied 261 



An important conclusion from these experiments is, that the 

 cellulose and pentosan constituents of these tissues exist together, 

 in combination rather than in mere admixture, the complex also 

 containing the characteristic lignin groups. (See Ligno celluloses, 

 p. 156.) 



General Methods for Identification of Carbohydrate Groups 

 (Hexoses, Pentoses, &c.} 



The researches of Tollens and others (Landw. Vers.-Stat. 39, 

 401) have contributed considerably towards the completion of 

 methods of proximate resolution of such mixtures as it has been 

 customary to define by the term ' non-nitrogenous extractive matters. 

 In the investigation, more particularly of vegetable food-stuffs and 

 fodder plants, the so-called * Weende ' method of Henneberg has 

 been generally adopted. This consists in the direct determination 

 of fat, protein, { crude fibre,' and ash ; and the sum of these consti- 

 tuents subtracted from 100 is represented as 'non-nitrogenous 

 extractives.' These are the less resistant carbohydrates in question, 

 and concerning these it is important to determine whether they 

 contain (i) the true (hexa) carbohydrates or their anhydrides ; and 

 (2) the presence or absence of (a) dextrose, () galactose, (c) levulose, 

 (d) other carbohydrates, more especially mannose ; and (3) the 

 presence or absence of the pentaglucoses. It is also often necessary 

 to estimate these compounds quantitatively. It is also necessary 

 to keep in view the probable presence of derivatives of these com- 

 pounds or group, more particularly the oxidised derivatives. It will 

 be obvious that no generally applicable scheme of analysis can be 

 laid down ; but the following methods of diagnosis are typical, and 

 should be carefully worked out by the student. 



(1) General identification of true (hexa} carbohydrates by levu- 

 linic acid reaction (Tollens, Ann. 243, 315). The substance is 

 heated for 20 hours at 95-98 with HCl.Aq (no). Levulinic acid 

 is extracted by exhaustion with ether, converted into the zinc salt 

 (cryst.), and this into the silver salt C 5 H 7 O 3 Ag, yielding 48-43 p.ct 

 Ag on ignition. 



(2) Identification of dextrose groups by Jormation of saccharic 

 acid. The substance is oxidised by digestion with HNO 3 (1-15 

 sp.gr.) ; the saccharic acid converted into the acid potassium salt, 

 and this into the silver salt, giving 50-94 p.ct. Ag on ignition. 



