168 QLUCOSIDES OTEER THAN TANNINS. 



water, but the latter solvent dissolves it with faciKty when 

 WBjmed. Dilute sulphuric acid resolves it into glucose, hydro- 

 quinone and methyl-hydroquinone. Both of the latter can be 

 extracted by shaking with ether, and, when warmed with' dilute 

 pulphuric acid and peroxide of manganese, yield qninpne, recog- 

 nisable by its characteristic iodine-like odour. Acetate of lead 

 does not precipitate arbutin. 



Daphnin^ differs from arbutin in being precipitated by acetate 

 of lead. It is sparingly dissolv'ed by cold, but freely by warm 

 yrater and by alcohol, and is insoluble in ether. Alkalies colour 

 it yellow. Acids and ferments resolve Jt' into sugar ahd daph- 

 netin; the latter can be partially sublimed without decomposi- 

 tion. Certain other constituents of mezereon bark yield umbelli- 

 ferone (§ 27) by dry distillation. 



Salicin crystallizes in colourless needles and scales, which have 

 a powerful action on polarized light, and are freely soluble in 

 boiling water and alcohol, but much less so in cold. It is insolu- 

 ble in ether. From aqueous solution it can be', extracted by 

 amylio alcohol (§ 56). Hydrate of lead does not combine with it. 

 Boiling with dilute, acids decomposes salicin into sugar and sali- 

 geniii or saUretin, both of which substances can be removed by 

 shaking with ether, If an Aqueous solution of salicin or saUgenin 

 is boiled with dilute sulphuric acid and bichromate of potassium, 

 salicylous acid is produced. (Cf. § 25.) Cone, sulphxiric acid 

 dissolves salicin, saligenin, and saliretin -with production of a iine 

 red colour, Salicin strikes a beautiful violet with Frohde's reagent. 

 These reactions can also be employed for the microckemical detec- 

 tion of. salicin. 



Pupidin yields benzoic acid in addition^ to the above-mentioned 

 decomposition-products when acted upon by dilute acids (cf. 

 § 26)j and saliiylons acid when warmed with chromic acid. With 

 cone, sulphuric acid a red colouration is developed, and with 

 Frohde's reagent a violet, whifch, however, is somewhat less intense 

 than that yielded by salicin under similar cgnditibns. It is con- 

 siderably less soluble than the latter in water and in alcohol,' and 

 can be removed from aqueous solution not only by amylic alcohol 

 (like salicin), but also by chloroform and (with difficulty) by 



* Compare' Zwenger, Annal. d. Chem. nnd Pharm. xo. 63, 1858 (Amcr. 

 Journ. Pharm. xxxiii. 325). 



