LIGNIN, CELLULOSE, ETC a6 



VIIL 



Determination op Lignin and Allied Substances and 

 OP Cellulose. 



§ 116. Lignin, , JncrusHng arid Cuticular Substances. — The resiaue 

 of the powder insoluble in all the foregoing menstrua, after 

 treatment aa 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 CO. for every gram of substance), until the colour 

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

 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 

 incntsHng- substances, the majority of the svherin and cuUcuiar sub- 

 sto/nce. (Cf. § 247.) Bromine-water has been proposed in the 

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



With regard to the Trdcrochemicat examination, I may- observe 

 that lignified tissues absorb fuchsin 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-Iignified tissue. Russow^ recommends the object 

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

 aniline-Ted. 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^ macerates in a dilute solution of chlorinated 

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



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

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



