402 ERICACEAE. 



acid, on the other hand, Kinone, C'H'O', 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 helou^- 

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

 Arctostaphylos glauca Swindley, OauUheria jorocumhens L. (Winter- 

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

 isolated arbutin from Kalmia latifoUa L. (Spoonwood), where it occurs 

 in smaller quantity than in bearberry leaves. 



Kinic acid (see p. 368) is probably absent in all these plants con- 

 taining arbutin. 



TJloth (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 EricoUn, 

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

 other Ericacece. EricoUn 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 

 Qi«jji6Q_ rpj^g ^^^^^ ^^ C-"ff^O-, is to be assigned to Ursone, whicn 

 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 crystal] izable substance. It melts at 20U ^t., 

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

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

 bearberry. 



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



the 

 the 



aqueous 



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

 produced, which quickly turns blue. By using ferric chloride, a biuii^ 



lied 



black precipitate immediately separates! 



Adulteration— The leaves of Vaccinium Viti s^dm Uj^^^^. 



Wl 



bearberry, which in form they much resemble. But they aie ^o. 

 distinguished by being somewhat crenate towards the apex, dotteci . 

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



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



w 



^ Gmelin, CJienmtnj, xvi. (1864) 28. 





^ 

 J 



