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 H 7 1^0 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. 



( C 2 IF 

 Orcin-monethylether, C 7 H 6 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 



