L1GNIN. 759 



according to M. Payen, of two organic principles, which he 

 has succeeded in separating ; one is the primitive tissue, com- 

 posing the vessels of the wood, which is isomeric with starch, 

 C 12 H 10 O 10 , and is named by him cellulose ; the other fills the 

 cells, and constitutes the true ligneous matter. M. Payen 

 obtained cellulose by the action on the sawings of beech-wood 

 of several times its weight of the most concentrated nitric acid, 

 which leaves that principle, while it dissolves the lignin. Cel- 

 lulose is dissolved by concentrated sulphuric acid, without 

 blackening, and is then converted into dextrin. The true lignin 

 of lint, hemp, straw, and linen cloth, was found by Payen to be 

 C 35 H 24 O 20 . Oak-wood, by the analysis of Gay-Lussac and 

 Thenard, is C 36 H 22 O 22 . Hemp, straw, etc. mixed cautiously 

 with concentrated sulphuric acid, so as to prevent elevation of 

 temperature, form, besides dextrine, a lignin-sulphuric acid, 

 analogous to benzo-sulphuric acid, which forms soluble salts 

 with barytes and oxide of lead. The dextrin formed when 

 lignin is dissolved in sulphuric acid, is converted by dilution 

 and boiling, into starch sugar. Sawdust, gum and starch dis- 

 solve in the most highly concentrated nitric acid (page 295), 

 without decomposition of the acid, and if immediately diluted 

 with water, give a white pulverulent neutral substance, insoluble 

 in water, which contains the elements of nitric acid and is 

 highly combustible (Robiquet). 



Lignin combines with several neutral salts, such as chloride 

 of mercury, sulphate of copper, and acetate of iron, with all of 

 which, particularly the first, wood is impregnated, in order to 

 preserve it from dry rot, a species of decay to which wood is 

 subject. The wood loses all its cohesion, and becomes friable 

 when affected by dry rot, and fungi generally appear upon it, 

 but the first destructive change is probably of a chemical kind 

 allied to the action of fermentation. Dr. Boucherie has found 

 that wood may be completely charged with solutions of salts 

 for its preservation, by aspiration from the roots or base of the 

 trunk of the tree, shortly after it is cut down, and has made many 

 other new observations on the subject.* 



Suberic acid, HO + C 8 H 6 O 3 , is formed among other products 

 by the action of moderately concentrated nitric acid, with heat, 



* Annalcs de Chiui. etc. Ixxiv. 1 13. 



