78, 79, 80. SAPONIN; ORGANIC ACIDS. 69 



exhausted by boiling with alcohol and filtering whilst hot, the 

 alcohol being recovered from the filtrate by distillation. The 

 residue is freed from fatty oil by ether, dissolved in water and 

 the saponin in it precipitated with baryta as before. 



B. The saponin-baryta obtained by the previous method is- 

 dissolved in water with the aid of hydrochloric acid and freed 

 from baryta by the cautious addition of dilute sulphuric acid. 

 The filtrate and washings from the sulphate of barium are boiled 

 for an hour ; the sapogenin which has separated out is filtered 

 off, washed, transferred together with the filter to a small flask 

 and exhausted by boiling with 83 per cent, of alcohol. On 

 evaporating the filtered alcoholic solution and drying at 110 the 

 weight of the sapogenin is ascertained and may be calculated to 

 saponin, 100 parts of the latter yielding on an average 3 5' 8 parts 

 of the former. 



Christophsohn obtained the following results in a series of 

 comparative experiments with both methods. The seeds of 

 Agrostemma githago were treated as directed in A. 



A. B. 



1. Quillaja saponaria (bark) ... ... 8'67 8 82 % Saponin. 



2. Gypsophila struthium (root) ... 14*59 15*0 



3. ,, ,, ... 13-31 13'2 



4. Saponaria officinalis (root) ... ... 478 5 '09 * 



5. Agrostemma githago (ripe seeds) ... 6'67 6*51 



In the various sarsaparillas Otten found, by method A, from 

 1*21 to 3 '43 per cent, of saponin. (See also 167.) 



79. Digitonin, which is allied to saponin, may be distin- 

 guished by its assuming a fine red colour when heated with 

 dilute sulphuric or hydrochloric acid. Like saponin, it is easily 

 soluble in cold water, sparingly in cold absolute alcohol. (Of. 

 & 155, 1&7.) 



EXAMINATION FOR ACIDS, ETC. 



80. Estimation of Total Organic Acids. Part of the filtrate 

 obtained in 73 and 76 is concentrated and, after complete 

 dissipation of the alcohol, precipitated with neutral acetate of lead, 

 avoiding an excess. After standing from twenty-four to forty-eight 

 hours the precipitate is filtered off and treated as directed in 49. 

 The organic matter present is noted as organic acids and allied 

 substances. If the presence of tannic acid, which has escaped re- 

 moval by the previous treatment with alcohol, is suspected, it 



