402 ERICACE^. 



By heating arbutin with peroxide of manganese and dilute sulphuric 

 acid, on the other hand, Kinone, C^IVO', and formic acid are produced. 

 If a concentrated decoction of the leaves is allowed to stand for some 

 months, a decomposition of the arbutin takes place, and a certain quan- 

 tity of hydrokinone can be isolated by shaking the liquid with ether. 



Arbutin is apparently widely distributed among the plants belong- 

 ing to the order Ericaceae. Maisch in 1874 showed it to occur in 

 Arctostaphylos glauca Swindley, Gaultheria procunibeiis L. (Winter- 

 green) and several other allied American plants. Kennedy (1875) 

 isolated arbutin from Kalniia latifolia L. (Spoonwood), where it occurs 

 in smaller quantity than in bearberry leaves. 



Kiuic acid (see p. 363) is probably absent in all these plants con- 

 taining arbutin. 



Uloth (1859) had already noticed pyrocatechin (p. 244) and hydro- 

 kinone among the products of the distillation of an aqueous extract 

 of bearberry leaves. Arbutin itself also yields hydrokinone by means 

 of dry distillation. Hydrokinone forms colourless crystals, melting at 

 169° C. 



In the mother liquor from which the arbutin has crystallized, there 

 remains a small quantity of the very bitter substance called Ericolin, 

 occurring in greater abundance in Calluna, Ledum, Rhododendron, and 

 other Ericacext}. Ericolin is an amorphous yellowish mass, softening 

 at 100° C and resolved, when heated with dilute sulphuric acid, into 

 sugar and Ericinol, a colourless, quickly resinifying oil of a peculiar, 

 not disagreeable odour; its composition^ agrees with the formula 

 Q10JJ16Q rpj^g ^^^^^ ^^ C-"ff-0-, is to be assigned to Ursone, which 

 H. Trommsdorff, in 1854, obtained from bearberry leaves by exhausting 

 them with ether (in which however it is but slightly soluble). Ursone 

 is a colourless and tasteless crystallizable substance. It melts at 200° C, 

 and sublimes apparently unchanged. Tonner (1866) met with it in the 

 leaves of an Australian Epacris, a plant of the same order as the 

 bearberry. 



Lastly, tannic acid is present in the leaves under notice ; their 

 aqueous infusion is neai'ly colourless, but assumes a violet hue on addi- 

 tion of ferrous sulphate. After a short time a reddish precipitate is 

 produced, which quickl}' turns blue. By using ferric chloride, a bluish 

 black precipitate immediately separates. 



Adulteration — The leaves of Vaccinium Vitis-idcea L., called 

 Red Whortleberry or Coivberry, have been confounded with those of 

 bearberry, which in form they much resemble. But they are easily 

 distinguished by being somewhat crenate towards the apex, dotted and 

 reticulate on the under surface and more revolate at the margin. 



Uses — An astringent tonic used chiefly in affections of the bladder. 

 1 Gmelin, Chemistry, xvi. (1864), 28. 



