68 SUBSTANCES SOLUBLE IN WATER. 



remains in solution, and is left behind on evaporating the 

 alcoholib filtrate. It is soluble in hot 83 per cent, spirit and 

 deposited again on cooling ; but in absolute alcohol it is alniost 

 insoluble. Baryta-water precipitates it from aqueous solution; 

 after washing with saturated baryta-water the saponin may be 

 liberated from the compound by carbonic acid gas ; a few per cent, 

 of baryta, however, always 'remain associated with the saponin 

 thus obtained. It also forms an insoluble compound with basic 

 acetate of lead. Its solutions have an unpleasant acrid taste, 

 froth on shaking, emulsify oils, etc. On agitating with chloro- 

 form it is taken up by that solvent and may be obtained in aii 

 amorphous condition by evaporating the, chloroformic solution. 

 (Of. § 55.) The residue, moistened with a few drops of concen- 

 trated sulphuric acid and exposed to the air, gradually assumes a 

 reddish or reddish-violet colouration. It is a glucosidie,' yielding 

 sapogenin as a fesinous decomposition product sparingly soluble 

 in water. 



§ 78. Quantitative Estimation. — Christophsohni and Otten^ have 

 adopted the following two methods for the determination of 

 saponin : 



A. 10 grams of the powdered substance are boiled three times 

 in succession with distilled water, the decoctions strained (they 

 filter very slowly), evaporated to a small bulk, precipitated with 

 alcohol and filtered. The precipitate is exhausted with boiling 

 alcohol (83 per cent.), and the spirituous solution added to the 

 filtrate. After recovering the alcohol by distillation the residue 

 is dissolved in water, concentrated and precipitated with saturated 

 baryta-water. The precipitate is collected on a tared filter, washed 

 with saturated baryta-water till the washings are colourless and 

 dried first at 100°, subsequently ' at 110°. After weighing it is 

 ignited till the ash is white, the baryta estimated as carbonate in 

 the usual way, calculated into oxide and deducted from the weight 

 of the saponin-baryta, the difference being the weight of saponin 

 from 10 grams of substance. For the seeds of Agrostemma 

 githago the following modification must be adopted on account 

 of the large amount of starch rendering the extraction with water 

 very tedious. A weighed quantity of ground air-dry seeds are 



^ 'Vergl. Unters. iiber das Saponin, etc' Diss. Dorpat, 1874, and Archiy 

 d. Pharra. vi. 432, 481. 

 ' Histiol. Unters. der SarsapariUen. Diss, Dorpat, 1876. 



