76 VEGETABLE SUBSTANCES. 



Cellulose swells in an aqueous solution of po- 

 tassic hydrate, as well as in the so-called min- 

 eral acids, and the stratification of the cell-wall is 

 frequently rendered much sharper and more dis- 

 tinct as a result. It is dissolved by concentrated 

 sulphuric acid with the formation of amyloid, and 

 in cuprammonia without change. From this solu- 

 tion it can be precipitated by the use of absolute 

 alcohol. 



Cellulose is colored with unequal intensity by 

 the various aniline colors. Alcannin and car- 

 mine, on the other hand, are inactive, or nearly so. 

 After heating with concentrated potassic hydrate, 

 young cellulose is not colored by cupric sulphate ; 

 but when somewhat older it is colored pale blue by 

 this reagent. Grenadier's alum carmine colors it 



LIGNIN. 



This substance probably consists of, i, vanillin ; 

 2, coniferin(?) ; 3, some gum ; 4, a substance which 

 is colored yellow by hydrochloric acid; and 5, the 

 wood-gum of Thomsen. It is thus seen to be a 

 very complex substance. 1 



Lignified cell-walls are colored yellow by chlor- 

 iodide of zinc. Concentrated sulphuric and chro- 

 mic acids dissolve them, but they are insoluble in 

 cuprammonia and the Schultze maceration fluid. 

 After treatment with an aqueous solution of cupric 



l Max Singer: Anzeiger des kais. Akad., Wien, 1882, No. u. 



