164 



GLUCOSIDES OTHER THAN TANNIN*. 



pitated by acetate of lead. Boiled with dilute [hydrochloric acid 

 it yields rhinanthogenin, which is of a dark bluish-green colour, and 

 insoluble in water. 



Some alkaloids, too, possess the property of yielding, under 

 similar conditions, deeply coloured decomposition-products, as for 

 instance, rhoeadine, thebaine ( 189). 



167. Other important Glucosides; Sulubilit-y. A remarkable 

 peculiarity of the above, as well as a number of other glucosides, 

 is that, although more or less easily dissolved by alcohol, they are 

 sparingly or not at all soluble in ether. Certain glucosides that 

 have been mentioned, where necessary, in the foregoing chapters 

 show a similar insolubility in ether (compare convolvulin, 153; 

 digitalein and digitonin, 155; chrysophan, 148, etc.); in fact, this 

 negative property may be said to be characteristic of the majority 

 of glucosides. 



Nitrogen enters into the composition of some few of the members 

 of this class, and certain of them, when acted upon by ferments or 

 acids, yield in addition to sugar a volatile decomposition-product of 

 characteristic odour ; but this is not the case with most of them. 



The following are some of the better-Jcnown glucosides that are 

 soluble in alcohol, contain nitrogen, and yield a volatile decomposition- 

 product. 



Amygdalin and laurocerasin 1 are both tolerably easily soluble in 

 water (amygdalin in 12 parts), and in boiling alcohol of sp. gr. 

 0'819, but more sparingly in cold. They are insoluble in petro- 

 leum spirit, and are precipitated by ether from alcoholic solution. 

 Amygdalin crystallizes with facility in bitter scales belonging to 

 the monoclinic system. Laurocerasin has not yet been obtained 

 in crystals. They are both laevo-rotatory. Cone, sulphuric acid dis- 

 solves them with pale reddish-violet colour. Emulsin easily resolves 

 them into glucose, oil of bitter almonds, and hydrocyanic acid, 

 the latter body being produced in larger quantity from amygdalin 

 than from laurocerasin. The reason for this is to be found in 

 the fact that in laurocerasin half of the cyanogen in the amygdalin 

 group has been already converted into formic acid, so that lauro- 

 cerasin may be regarded as amygdalate of amygdalin. On boiling 

 amygdalin and laurocerasin, therefore, with baryta-water, the 

 former will yield one molecule of ammonia for every molecule of 





1 Compare Lehmann, * Ueber das Amygdalin der Kirschen, Pflaumen,' etc., 

 Diss. Dorpat, 1874, 



