SO PROPERTIES OF WOOD. 



Cieslar* has shown that the amount of lignin in wood 

 increases when a tree receives increased light and heat, which 

 therefore affect all the technical properties of wood ; these, 

 therefore, depend chiefly on the relative volumes of cellulose 

 and lignin in the wood. Unlignified tissues practically mean 

 wood-formations that are not completed during late summer 

 and are killed by early or winter frosts. It is not the absence 

 of lignin in the cellulose walls that causes the susceptibility 

 to frost, for neither cellulose nor lignin freeze, but the 

 presence of plasma that is still constructive and has not 

 passed over into its resting (winter) condition. 



The presence of lignin in wood may be tested in various 

 ways. Pure cellulose is coloured violet by chloro-iodide of 

 zinc ; lignified cell-walls are coloured cherry-red on the 

 application of phloroglucin and hydrochloric acid ; yellow 

 by sulphate of anilin ; and sky-blue under sunlight by a 

 solution of phenol in hydrochloric acid. 



By boiling wood in a solution of soda or caustic soda, or 

 in a solution of calcium sulphate, lignin is removed from 

 the cell-wall and pure cellulose is obtained. 



Many fungi that are destructive to wood attack its lignin 

 and leave the cellulose intact, whilst other fungi dissolve the 

 cellulose, leaving a brittle, brown ligneous mass that may be 

 pulverised by the fingers. 



A chemical combination of the cell-wall with salts of 

 alumina, such as was attempted in Haselmann's process for 

 hardening wood, does not appear to be practicable ; the 

 alumina is merely attached to the wood and may be removed 

 by rain, etc. 



When wood is burned, its ash-constituents persist as a pale 

 grey powder containing the mineral constituents of the wood. 

 They are simple or double salts of potash, soda, magnesia, 

 manganese, ferric-oxide, calcium-oxide, etc., combined with 

 silicic, phosphoric, carbonic, acetic, pommic and citric acids. 

 Although some of these constituents are essential for the life 

 of plants, their effects on the quality of wood appear to be but 

 slight; i.ln-.y penetrate it in all directions as an extremely fine 

 iiiiiionil skeleton. Carbonate of potash is an economic product 



* A. ricsbir, " Untersuchung liber den LigningehalteinigerNadelholzer/' isi)7. 



