54, 55, 56. FROM ACID SOLUTION. 49 



repeated until only traces of the substance are dissolved. Then, 

 and not till then, the same treatment is repeated with the next 

 solvent, and so on. All liquids employed for agitation must be 

 rectified shortly before being used. Petroleum spirit must be 

 as volatile as possible; benzene should boil constantly at 81 C., 

 and yield mtro-benzene when treated with fuming nitric acid. 



55. From Acid Solution. Of the better-known bitter prin- 

 ciples, acids and alkaloids removed by petroleum spirit from an acid 

 .solution, the following may be mentioned : 



Salicylic acid (cf. 26). Pungent principles of capsicum, etc. 

 { 126). (Both of these would have been already detected in 

 the ethereal extract. Salicylic acid may be more easily removed 

 by benzene or ether.) Piperin the majority of this principle 

 will be found in the part of the alcoholic extract insoluble in 

 water (compare further 171, 178). Absyntliin i cannot be 

 completely removed by petroleum spirit ( 156). Hop-resin 

 (156). 



Benzene removes from the same solution santonin (cf. 154); 

 caryophyllin ( 156) ; cubebin ( 155) ; digitalin (remains principally 

 in that part of the ethereal extract which is insoluble in water 

 (cf. 155) ; cjratiolin ( 167) ; cascarillin ( 156) ; elaterin ( 156) ; 

 populin ( 167); colocyntliin ( 167); absynthin ( 156); quassin 

 ( 156); menyanthin ( 167); ericolin ( 155); daphnin ( 167); 

 Utter principle of Cnicus benedictus ( 168); caffeine ( 171, 176); 

 piper'm (see above); colckiceme ( 171); berberine is dissolved by 

 benzene in small proportion only (compare 171). 



Besides the substances already named as being dissolved by 

 petroleum spirit and benzene, chloroform removes also among 

 others : Betizoic acid (cf. 26) ; digitalein (sparingly soluble in 

 ether, 155); convallamarin ( 167); saponin (insoluble in ether, 

 difficultly soluble in absolute alcohol, 77 et seq., 167); senegin 

 (the B&me) ; physalin ( 167); syringin ( 167); cesculin ( 167); 

 jiicrotoxin ( 155); helleborein ( 167); cinchonine (is insoluble 

 in ether, 171, 182, 184); theobromine ( 177); papavervne 

 ($ 171); narceine ( 171). Colchicine, solanidlne, quebrachine, 

 (jeissospermine. 



56. From Alkaline Solution. After the last agitation with 

 chloroform the aqueous liquid should be shaken whilst still acid 

 with petroleum spirit. This removes the small quantity of 

 chloroform remaining dissolved by the watery liquid. An error 



4 



