294 



INDUSTRIAL PLANTS 



logwood of itself does not make a permanent dye. It requires 

 the use of a mordant, that is to say, some substance such as 

 a salt of iron which fixes the dye upon the fabric. Thus used 

 it makes one of the best blacks for wool or cotton. In com- 

 bination with iron, etc., it is used also A\ddely in the manu- 

 facture of writing inks. 



Lampblack is the finely divided carbon deposited from 

 the smoke of rosin or oil burned with slight access of air in 



Fig. 276. — Logwood-tree {Hwmatoxylon campecheanum, Pulse Family, 

 Lcguminosw) . A, flowering branch. B, flower. C, same, cut verti- 

 cally. D, pod. (Taubert.) — Tree about 8 m. tall; leaves smooth; 

 flowers yellow, fragrant; fruit dry. Native home, Tropical America. 



a special chamber. It is used extensively in the making of 

 printing-ink, and forms the basis of incha-ink and of various 

 black pigments used in painting, leather-finishing, and the 

 like. Lampblack is one of the most important of coloring 

 matters. 



Tan-bark is obtained from many trees, including hem- 

 lock (Fig. 263), oak (Fig. 243), willow (Fig. 228), chestnut 

 (Fig. 24), larch (Fig. 259), and spruce (Fig. 260), which are 

 rich in tannins. These substances, as already explained in 

 sections 57 and 60, are astringents which are present in 



