68 SUBSTANCES SOLUBLE IN WATER. 



remains in solution, and is left behind on evaporating • the 

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

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

 insoluble. Baryta-water precipitates it from aqueous solution ; 

 after washing Avith 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 an 

 amorphous condition by evaporating the chloroformic solution. 

 (Cf. § 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 glucoside, yielding 

 sapogenin as a resinous decomposition product sparingly soluble 

 in water. 



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

 adopted the follo^Wng two methods for the determination of 

 saponin : 



A. 10 gi'ams of the powdered sulistance 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 vnih saturated 

 haryta-water. The precipitate is collected on a tared filter, Avashed 

 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 diff'erence 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 arc 



1 ' Vergl. Unters, über das Saponin, etc' DLss. Dorpat, 1874, and Archiv 

 d. Pharm, vi. 432, 481. 



^ Histiol. Unter«, der Sarsaparillen. Diss. Dorpat, 1S7G. 



