CHEMICAL SCIENCE. 287 



somewhat yellowish, and becomes colored in a decoction of logwood. 

 The red and rose from garancine and garancenx differ from the above 

 colors in not bearing brightening with soap, acids, and alkalies. When 

 treated with hydrochloric acid, they pass into orange, and do not then 

 give a violet, but a dull blue color, with milk of lime. 



The tone of color is sufficient to distinguish between colors pro- 

 duced from garancine or garanceux, the latter possessing an orange 

 shade. When the red is accompanied by violet, the distinction is still 

 more easy, because garancine yields a violet, which is nearly as beau- 

 tiful as that from madder, while the madder of garanceux is more 

 reddish-gray. 



The red colors from Brazil-wood and cochineal, when treated with 

 hydrochloric acid and tin salt, become gooseberry-red; and then 

 milk of lime produces a violet of little permanence, which disappears 

 entirely on subsequent boiling with soap, while the madder colors ac- 

 quire their greatest brilliancy by this treatment. 



The red from cochineal differs from that of Brazil-wood in tone, and 

 in its behavior with concentrated sulphuric acid ; the former becomes 

 bright cherry-red, the latter orange. 



Yellow Colors. The yellow of quercitron is discharged by chlorine 

 and sulphurous acid, but it is not sensibly changed to orange by either 

 caustic potash or tin salt. 



The yellow of buckthorn-berries is likewise destroyed by chlorine ; 

 caustic potash renders it bright yellow. Heated with tin salt, it passes 

 into orange ; with sulphuric acid, it acquires a stone color. 



The orange and nankeen colors from fustic and fustet are changed 

 to red by sulphuric acid ; treated with potash, they acquire a color 

 resembling that of catechu ; they are discharged by nitric acid. 



The yellow green from sumach acquires greater brightness with tin 

 salt ; with nitric acid, it becomes red ; sulphuric acid does not produce 

 much alteration; sulphate of iron changes it to gray. 



The yellow from arnotto is but little affected by chlorine ; concen- 

 trated sulphuric acid changes it to bluish green ; with nitric acid it 

 assumes a dark color, and then disappears entirely. 



Chrome-yellow is unaltered by heating with weak hydrochloric 

 acid, but destroyed by the concentrated acid. It is destroyed by 

 caustic alkalies ; boiling potash converts into orange. Chrome orange 

 becomes greenish-yellow when treated with weak acids. 



Black Colors. Logwood-black contains iron as a mordant, some- 

 times iron and alumina. In the latter case it has a shade of blue. 

 Such a color is discharged by chloride, a yellow resulting from the 

 iron ground remaining. Treated with hydrochloric acid and tin salt, 

 it becomes red, with the former more cherry-red, with the latter vio- 

 let-red. 



The blacks from astringent substances are easily recognizable by 

 the shade of olive which they present. When treated with hydro- 

 chloric acid, they acquire a dull orange color ; tin salt dissolves the 

 iron, and changes the color to a dirty olive. 



Chrome-black may be known by its behavior with chloride of lime, 



