226 THE CARBOHYDRATES 



Lignin Isolated by Acid Treatment, 



Methods for the isolation of hgnin from Hgno-cellulose have 

 also been devised which depend on the solubility of cellulose 

 in strong acids, the lignin remaining undissolved ; for this 

 purpose Ost and Wilkening * employ 72 per cent sulphuric 

 acid, while Willstatter and Zechmeister f recommend concen- 

 trated hydrochloric acid, either acid being allowed to act in 

 the cold. 



Analyses of the lignin isolated by these methods, however, 

 show that lignin has undergone some degree of hydrolysis, 

 since it contains fewer methoxyl groups as compared with 

 lignins prepared by other methods. 



Cross and Bevan isolated from hgnin, by the action of 

 chlorine, a compound which contained chlorine and had the 

 properties of a ketone ; from this and other evidence they 

 propose the following formula for lignin : — 



ABC D 



CO 00 



y\ y'\ y\ yOU Ca cellulose. 



HC CH - (CHaCO)^ - HC CH . CH-CH . CH<^ \ 



II I II ^OH lj3 cellulose. 



HC CO CH3OHC CH.OCH3 



CH2 CO 



in which A is the group which is attacked by the chlorine, 

 B gives rise to the acetic acid obtained by hydrolysis or 

 distillation, and D is the aldehyde group to whose two-hydroxyl 

 group cellulose a and 8 are supposed to be attached in ester- 

 hke combination ; it is, however, not easy to see how his 

 compound which contains Cjo should give rise to a lignone 

 chloride containing Cjq. 



Estimation of Lignin. 



The methods for estimating lignin are based upon the use 

 of mineral acids under various conditions with the object of 



• Ost and Wilkening : " Chem. Zeit.," 1910. 34, 461. 

 I Willstatter and Zechmeister: " Ber. deut. chem. Gesells.," 1913. 

 46, 2401. 



