166 GLUCOSIDES OTHER THAN TANNINS. 



by emulsin) into volatile oil of mustard (sulphocyanide of allyl, 

 § 29), characterized by its extreme pungency, glucose and bisul- 

 phate of potassium. A quantitative estimation might possibly be 

 made by freeing the finely-powdered seeds from oil, exhausting 

 with warm 85 per cent. sjDirit, and digesting the tincture for 

 some time ynih. carbonate of barium. From the filtrate the 

 alcohol might be recovered by distillation, the residue dissolved 

 in water, and digested with myrosin at a temperature of about 40°, 

 the barium being finally precipitated as sulphate by the addition 

 of hydrochloric and sulphuric acid. One molecule of sulphate of 

 barium indicates one of myronic acid.^ 



White mustard contains no myronic acid, but in its stead 

 another glucoside, to which the name of s'malh'iii has been given. 

 Like myronic acid, it dissolves in boiling 85 per cent, spirit, 

 separating out again to a great extent on cooling. It is crystal- 

 line, insoluble in ether and bisulphide of carbon; sparingly 

 .soluble in cold, freely in hot alcohol, and in water. Alkalies 

 colour it 'yellow, nitric acid transiently blood-red. It reduces 

 alkaline copper solution, and is i)recipitated by mercuric chloride 

 and nitrate of silver. Warm solution of caustic soda converts it into 

 suljihate and sulphocyanide of soda; myrosin into glucose, acid 

 suljihate of sinapine and sulphocyanate of acrinyl (C-H-.0, NCS). 

 Sulphocyanate of sinapine, which also occurs in Avhite mustard, is 

 not glucosidal, and differs from sinalbin in being more easily 

 soluble in cold alcohol, and in yielding the sulphocyanide reaction 

 directly with ferric chloride.'-^ 



EricoUn and meni/cmthin^ are glucosides containing no nitrogen, 

 but yielding easih/ volatile decomposition products. The former 

 has been described in § 155. Menyanthin is freely soluble in 

 warm water and in alcohol, but insolul^lc in ether. Cone, sul- 

 phuric acid dissolves it with the gradual production of a reddish- 

 violet colouration. Warming with dilute sulphuric acid resolves 

 it into glucose and menyanthol, tlic latter possessing a penetrating 

 odour. Menyanthin is precii)itated by tannic acid, but not by 

 acetate of lead. 



^ Compare Will mid Körner, Anna!, tl. Chem. und rhiirm. cxxv. 257, 1863. 

 (^Vm. Journ. I^harin. xxv. 3"23.) 



- Compare \\'ill und Lavibenheimer, Annal. d. Chem. und Pharm, cxcix. 

 150, 1879 (Pharm. Journ. and Trans. [■'>], x. 918). Babo und Hirschbrunn, 

 ibid. Ixxxiv. 10, 18.^.2. 



" Compare Kromayer, loc. rll. ; Liebelt, Jahresb. f. I'harni. 119, 1877. 



