384 VEGETABLE SUBSTANCES. 



of timber trees, any farther description here would 

 therefore be superfluous. The quantity of colouring 

 matter contained in this bark is very great compared 

 to its weight; while the beauty of the colour it imparts 

 is nearly equal to that of weld, and its durability is 

 superior. According to Dr. Bancroft, it is capable 

 alone of producing more cheaply all, or very nearly 

 all, the effects of every other yellow dyeing drug. Its 

 value is now fully appreciated, and a large quantity is 

 annually imported from America into this country. 



The epidermis, or exterior blackish coat of this 

 bark, affords a yellow colour, but less pure than the 

 other parts of the bark; it is therefore separated 

 from these, being shaven off with a sharp instrument. 

 The cellular and cortical parts which remain are 

 then ground in a mill, some falling into a light fine 

 powder, and the rest into stringy filaments ; this last 

 yields only half as much colouring matter as the 

 powder. These are seldom separated from each 

 other, however, but are used together as a dyeing 

 substance. In this state the bark yields as much 

 colour as about eight or ten times its weight, and one 

 hundred times its bulk of the weld plant. The 

 colouring matter is readily extracted by water, at a 

 temperature of 100 Fahrenheit. This decoction is 

 of a brownish yellow colour, which alkalis deepen and 

 acids brighten. All the different shades of yellow 

 may be produced by varying the quantity of colour- 

 ing matter. It is an adjective colour ; the mordants 

 used are nitro-muriate of tin and acetate of alumina. 

 Drab colours are obtained from the same dye, with a 

 mordant of sulphate of iron and carbonate of lime, 

 and olive shades by a mordant of sulphate of copper 

 and carbonate of lime. An extract may be made 

 from the bark amounting to about one-twelfth of its 

 weight, but its colour becomes injured by the appli- 

 cation of boiling heat, and therefore the extract can- 



