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 widely 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 
Fic. 276.—Logwood-tree (Hematoxrylon campecheanum, Pulse Family, 
Leguminose). A, flowering branch. 8B, 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 india-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 
