4 Dr. J. Stenhouse on Alpha- and Beta-Orcine. 



Examination of the Crystalline Form of Orcine. 



I transmitted a quantity of crystallized orcine to Professor 

 W. H. Miller of Cambridge, who has kindly favoured me 

 with the subjoined determination of its crystalline form. 



Oblique. Symbols, a 100, c 001, e 101, m 110. 



Orcine. 



Angles between normals to the faces. 



o I 



ae 43 44 

 ac 83 57 

 ma 51 12 

 mm' 77 36 



Cleavage parallel to a, very perfect. 



Beta- Orcine. 



The substance to which I have given the name of beta- 

 orcine is obtained from usnic acid, which is perhaps the most 

 widely diffused of all the known proximate principles of the 

 lichens. Knop found usnic acid in several species of Usnea, 

 such as Usnea Jloi'ida, U. hirta, and U. plicata. Messrs. 

 Rochleder and Heldt extracted it from the lichen Bangeferinus, 

 Usnea barbata, and Bamalinea calicaris. In addition to these 

 sources, I have found it in the Evernia Prunaslri and in Ba- 

 malinea Fraxinia. The best mode of extracting usnic acid, 

 as I have fully detailed in the paper already referred to, is by 

 macerating the lichens in milk of lime, and precipitating the 

 filtered solution by muriatic acid. 



Beta-orcine may be obtained from usnic acid by several 

 processes. The method which I have found most convenient 

 is by subjecting the crude usnic acid, previously dried, to de- 

 structive distillation. The beta-orcine sublimes, and is depo- 

 sited in long yellow crystals, partly on the neck and sides of 

 the retort ; but by much the larger portion of it is dissolved 

 in a brownish-coloured resinous liquid which passes into the 

 receiver. A very large quantity of a bulky porous charcoal 

 remains in the retort. 



The resinous fluid which has passed into the receiver must 

 be repeatedly treated with considerable quantities of boiling 

 water to dissolve out the orcine, which is retained by the resin 

 with great pertinacity. The solutions containing the impure 

 orcine should be concentrated to the consistence of a syrup, 

 and left standing for some time in a flat open vessel. In the 



