168 GLUCOSIDES OTHER THAN TANNINS. 



water, but the latter solvent dissolves it with facility when 

 warmed. 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 

 sulphuric acid and peroxide of manganese, yield quinone, recog- 

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

 does not precipitate arbutin. 



Daplinin 1 differs from arbutin in being precipitated by acetate 

 of lead. It is sparingly dissolved by cold, but freely by warm 

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

 it yellow. Acids and ferments resolve it into sugar and 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 

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

 Boiling with dilute acids decomposes salicin into sugar and sali- 

 genin or saliretin, both of which substances can be removed by 

 shaking with ether. If an aqueous solution of salicin or saligenin 

 is boiled with dilute sulphuric acid and bichromate of potassium, 

 salicylous acid is produced. (Of. 25.) Cone, sulphuric acid 

 dissolves salicin, saligenin, and saliretin with production of a fine 

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

 These reactions can also be employed for the microchemical detec- 

 tion of salicin. 



Populin yields benzoic acid in addition to the above-mentioned 

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

 26), and salicylous acid when warmed with chromic acid. With 

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

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

 than that yielded by salicin under similar conditions. 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 



1 Compare Zwenger, Annal. d. Chem. xmd Pharm. xc. 63, 1858 (Amer. 

 Journ. Pharm. xxxiii. 325). 



