308 ORCIN. 



with caustic potassa. In order to prepare it in large 

 quantity a lichen, belonging to the species roccella or 

 lecanora, is boiled with milk of lime, filtered, and the 

 filtrate evaporated to about one-fourth. The lime is 

 now precipitated by means of carbonic anhydride, and 

 the solution evaporated nearly to dryness over the 

 water-bath. The residue is boiled several times with 

 benzene, the orcin extracted from its solution in ben- 

 zene by shaking with water, and the aqueous solution 

 evaporated. Crystallizes in large, colorless, six-sided 

 prisms with 1 molecule of water of crystallization. 

 It has a repulsive, sweet taste. Easily soluble in 

 water, alcohol, and ether. With its water of crystal- 

 lization it fuses at 58, anhydrous at 86 ; it boils at 

 290 without undergoing decomposition. In contact 

 with the air it turns red. Its aqueous solution is 

 colored deep violet by iron chloride. 



Orcin combines with dry ammonia, forming a crys- 

 talline compound. Exposed to the simultaneous influ- 

 ence of moist air and ammonia, it is converted into a 

 dark brown substance orcein, C 7 IKN"0 3 , which dissolves 

 in alkalies, forming solutions of a beautiful red color; 

 from these solutions acetic acid precipitates the dis- 

 solved orcin. Upon this conduct depends the employ- 

 ment of a number of lichens in the preparation of the 

 beautiful red dyes, known as archil, cudbear, persio. 

 These dyes are obtained by mixing the finely-ground 

 lichens with decaying urine and lime, or with ammo- 

 nia-water, and allowing the mixture to stand for a 

 long time in contact with the air. Litmus is prepared 

 in the same way, particularly from Leconora tartarea. 



Orcin-monethylether, 7 H 6 j ^?*and -diethyl- 



ether, C 7 H 6 (O.C 2 H 5 ) 2 , are produced by the action of 

 caustic potassa and ethyl iodide on orcin. Both com- 

 pounds are syrupy liquids. The diethylether boils 

 without decomposition at 240-250. 



Diacetylorcin, C 7 H 6 (O.C 2 H 3 0) 2 , is formed, even at 

 the ordinary temperature, by pouring acetyl chloride 



