§ 167. BENZOHELICIN, ETC. 260 



"benzene (§ 55). Populin decomposes with far gieater facility 

 than saHcin. 



Beu-ohelicin,'^ detected by Johauson in willow bark, forms colour- 

 less crystals, soluble in Avater and alcohol. With cone, sulphuric 

 acid it turns yellow. Fröhde's reagent does not produce a violet 

 colouration. Boiling Avith not over-dilute hydrochloric acid 

 resolves benzohelicin into glucose, benzoic acid, and a resinous 

 substance that dissolves blood-red in cone, sulphuric acid. 



Philyrin^ is much less soluble in water and alcohol than is 

 ■salicin, and yields under the influence of dilute acids, glucose and 

 philygenin, a polymer of saligenin. Both philyrin and philygenin 

 dissolve in cone, sulphuric acid with red colouration. 



Phlorrhmn^ crystallizes in colourless needles sparingly soluble 

 in cold water-, easily in hot. Ethyl and methyl alcohol dissolve it 

 with facility, ether with difficulty. Dilute acids resolve it into 

 glucose and phlorrhetin. Cone, sulphuric acid forms red solutions 

 with both phlorrhizin and phlorrhetin ; with Fröhde's reagent a 

 splendid royal-blue colouration is rajiidly developed. Moistened 

 with ammonia and exposed to the air, phlorrhizin turns yellow, 

 red, and finally blue. 



jEsculin can likewise be obtained in colourless needles soluble 

 in 12 -5 parts of boiling, 672 of cold Avater; in 24 of boiling, and 

 120 of cold absolute alcohol. Chloroform removes it from 

 aqueous solution (i^ 55). Boiling with dilute acids resolves it into 

 glucose and ?esculetin. The latter yields a yellow solution with 

 alkalies ; it is also soluble iu bisulphite of ammonia, and if such a 

 solution be mixed Avith ammonia and shaken Anth air, at first 

 blood-red and sul^sequently a deep blue colour is developed. The 

 very characteristic blue fluorescence of aesculin is increased by 

 alkalies and destroyed by acids. 



Fraxin possesses a similar fluorescence, and can also be obtained 

 in colourless crystals. It is more sparingly soluble in Avater and 

 absolute alcohol than ?esculin, but more freely in ether, to Avhich 

 it imparts its fluorescence. Ferric chloride is said at first to strike 



^ See Johanson, loc. elf, Piria, Annal. d. Chem. und Pharm. Ixxxi. 24;', 

 1852; xcvi. 375, 1855 (Amer. Journ. Pharm, xxiv. 241, xxviii. 259). 



- Compare Campona, Annal. d. Chem. und Pharm. Ixxxi. 245, xcvi. -375. 



^ For isophlorrhizin, see Kochleder, Journ. f. pract. Chem. civ. 397, 1868 

 (Amer. Journ. Pharm, xli. 419). 



