LIGNIN, CELLULOSE, ETC. 95 



VIII. 



Determination of Lignin and Allted Sltbstances and 

 OF Cellulose. 



§ 113. Lignin, Lncrusting and Cidicular Substances. — The residue 

 of the powder insohible in all the foregoing menstrua, after 

 treatment as directed in § 109, is washed with water, dried, 

 and weighed. After having been again finely powdered, it is 

 macerated in freshly prepared chlorine-water (in the proportion of 

 about 100 cc. for every gram of substance), until the colour 

 changes to a pale yellow. If 2 to 3 days do not suffice, the chlorine- 

 water must be drawn off and replaced by fresh, and this treat- 

 ment repeated if necessary. It is finally collected on a tared 

 filter, and washed first with water, then with very dilute (0'3 per 

 cent.) solution of caustic potash until the washings are colourless, 

 the alkali being ultimately removed by pure water. The loss in 

 weight after drying represents the amount of lignin, the so-called 

 incrusting substances, the majority of the suherin and cuticular sub- 

 stance. (Cf. § 247.) Bromine-Avater has been proposed in the 

 place of chlorine-water, but it does not act so energetically. 



With regard to the microchemical examination, I may observe 

 that lignified tissues absorb f uchsin from its aqueous solution, and 

 retain it so tenaciously that they appear stained deep-red even 

 after maceration in glycerine, which removes all the colouring 

 matter from non-lignified tissue. Eussow^ recommends the object 

 to be placed on a slide with a drop of dilute aqueous solution of 

 aniline-red. A drop of glycerine is then brought into contact 

 with the edge of the coverslip on the slide, and left for twenty- 

 four hours. Stiles 2 macerates in a dilute solution of chlorinated 

 lime {1 in 60), then transfers for an hour to a solution of hypo- 



1 Sitz-ber. d. Dorpater Natiirf. Gesellsch. 1880, p. 419. 

 - Pharm. Journ. and Trans, [3], vi. 741. 



