LIGNIN 225 



for forty-eight hours ; they obtained a substance of molecular 

 weight 800 to which they assigned the formula C4oH440ig 

 which they claimed contained four methoxyl and four hydroxyl 

 groups. 



Mehta,* in attempting to devise a method for the quantita- 

 tive estimation of lignin, recommends heating in the autoclave 

 with 4 per cent caustic soda under a pressure of 10 atmospheres 

 for one hour. On precipitating with acid a lignin was obtained 

 which, when purified by extraction with alcohol, was an 

 amorphous, faintly acid substance with a pleasant aromatic 

 odour and melting at 170° ; its iodine value was found to be 



1397- 



Doree and Barton-Wright, f employing the above con- 

 ditions and working with spruce wood previously extracted 

 with benzene, alcohol, and water, isolated a substance with 

 melting-point 186° to which they assign the fornmla 

 CaoHaoOg which, though agreeing with that assigned by 

 Klason to a-lignin, has approximately half the molecular 

 weight of the formulse suggested by earlier workers. This 

 substance, which they propose to call meta-lignin, has one 

 hydroxy], two methoxyl, and two carboxyl groups, one alde- 

 hydic, and the other ketonic. They suggest that meta-hgnin 

 is the unit upon which the natural lignins are based and that, 

 whilst the usual type isolated is of the order C40, it may exist 

 in the plant in an even more polymerized form. They suggest 

 for meta-lignin the extended formula — 



CioH,jO(OCH3)2 . OH . CO . CHO 



Doree and Barton-Wright disagree with Klason's formula 

 on the ground that no aromatic compounds are obtained from 

 lignin on oxidation, and they suggest, as an alternative, that 

 lignin contains hydroaromatic nuclei which would account 

 both for the unsaturated properties of the substance and for 

 the profound disruption undergone by the molecule with 

 formation of oxalic and carbonic acids. 



* Mehta : " Biochem. Journ.," 1925, 19, 958. 

 t Doree and Barton-Wright : id., 1927, 21, 290. 



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