LIGNIN 221 



and also in the bark of the lime and in decayed oak wood ; 

 nevertheless, there is considerable doubt as to whether these 

 substances are universally present in lignified tissues other 

 than wood, although in the opinion of Klason lignin itself is 

 a condensation product of coniferyl alcohol (see below). 



It was first suggested by Nickel * that the colour reactions 

 of lignified tissue were due to the presence of an aldehyde 

 group in the lignin complex, more especially as the colour 

 reactions were not given by wood which had been treated 

 with sodium bisulphite and other reagents which would mask 

 its aldehydic properties. Czapek,t by a somewhat drastic 

 treatment of wood with stannous chloride, isolated a substance 

 which was both an aldehyde and a phenol ; to this substance, 

 which gave the colour reaction with phloroglucinol and hydro- 

 chloric acid, he gave the name of hadromal, without assigning 

 any constitution to it ; his views did not attain general 

 acceptance and were discredited especially by Grafe J ; since 

 then, however, Hoffmeister,§ modifying Czapek's original con- 

 ditions, has isolated from oak sawdust a substance of the 

 formula CjoHjoOs, which proved to be coniferyl aldehyde of 

 the formula — 



CH = CH . CHO 



-OCH3 



OH 



This substance, whose constitution was definitely estab- 

 lished by synthesis from vanillin and acetic aldehyde, gives 

 the colour reaction with phloroglucinol and hydrochloric 

 acid and would thus appear to be identical with Czapek's 

 hadromal. According to the view of Hoffmeister this substance 

 occurs to the extent of about 3 per cent as a cellulose ester 

 in wood. 



* Nickel : " Chem. Zeit.," 1887, 11, 1520. 



f Czapek : " Zeit. physiol. Chem.," iSgg, 27, 141. 



I Grafe : " Monatshefte," 1904, 25, 987. 



§ Hoffmeister : " Ber. deut. cfiem. Gesells.," 1927, 60, 2062. 



