ORCHIL. 151 



cohol ; the watery solution, which is of a fine, crimson, becomes 

 colorless in a fnw days when it is kept in a flask hermetically seal- 

 ed ; it regains its color by exposure to the air. The color which is 

 acquired during the manufacture of orchil indicates that the lichens 

 which yield it contain principles which are colorless in themselves, 

 but which possess the singular property of becoming tinted under 

 the influence of oxygen and ammonia ; for in the preparation of or- 

 chil, the addition of urine and of lime has no other purpose beyond 

 the introduction and development of this alkaline base. This view 

 is shown to be correct, moreover, by the facts brought to light by 

 MM. Heeren and Robiquet in their inquiries into the chemical con- 

 stitution of the lichens. These chemists, in fact, succeeded in ex- 

 tracting from several of the lichens which yield orchil a variety of 

 colorless crystalline principles, in particular orcine, a substance 

 which may be procured in very regular quadrangular prisms, and 

 which is soluble in water and in alcohol. The watery solution of 

 orcine mixed with ammonia and exposed to the air, becomes gradu- 

 ally of a deeper and deeper red until it has the color of blood. The 

 result of this oxidation of orcine under the action of ammonia is a 

 coloring principle, orceine, into the constitution of which azote en- 

 ters, an element which formed no part of orcine ; the analyses of 

 these two substances made by M. Dumas, show this fact very dis- 

 tinctly : 



Dry orcine. Orceine. 



Carbon 67.8 55.9 



Hydrogen 6.5 5,2 



Oxygen 25.7 31.0 



Azote -J 7.9 



100.0 100.0 



The lichens furnish several other principles analogous to orcine in 

 their property of acquiring color under similar circumstances. 



Turnsole. This coloring matter is met with in commerce in two 

 states, in mass and in thin cakes, and is procured from various 

 lichens which have not yet been accurately specified ; in any case 

 the substance is obtained by a process which differs little from that 

 used in the manufacture of orchil. According to Mr. Kane, the 

 coloring principles of turnsole are naturally red : they only become 

 blue by combining with a base. The coloring matters which pre- 

 dominate in turnsole are erythrolitmine and azolitmine, which are 

 united with lime, potash, and ammonia, and further mixed with a 

 considerable quantity of chalk and sand. The analyses of Kane 

 show these two substances to have the following composition : — 



Erythrolitmine. Azolitmine. 



Carbon 55.6 49.8 



Hydi-ogen 8.4 5.4 



Oxygen • 36.0 oxygen and azote 44.8 



100.0 100.0 



Turnsole occurs in trade in the shape of thin cakes, made up of 

 chips, which are colored by the juice of chroijophoria tincloiiaj a 

 plant of the euphorbiaceous family, and of which the dyeing pro- 

 perties appear to have been known to the eaiJiest natuialists. 



