§.§ 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 nitro-benzene vvhen treated with fuming nitric acid. 



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

 ciples, acids and alkaloids removed by fctrohum sjniii 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 princij^le 

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

 water (compare further §§ 171, 178). Absi/nthin cannot be 

 completely removed by petroleum spint (§ 156). Hop-resin 



a 156). 



Benzene removes from the same solution santonin (cf. § 15-4); 

 caryophyllin (§ 156) ; cuhebin (§ 155) ; digitalin (remains principally 

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

 (cf. §155); gratiolin (^ IQ7) ; cascariUi7i (^ 156) ; elateri7i (^ 156) ; 

 2)opulin (§ 167); colocynthin (§ 167); ahsynthhi (§ 156); quassin 

 (§ 156); menyanthin (§ 167); er'icoUn (§ 155); daphnin (§ 167); 

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

 piper in (see above); colchiceme (^ 171); ierJerme 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 : Benzoic acid (cf. § 26) ; digitalein (sparingly soluble in 

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

 difficultly soluble in absolute alcohol, § 11 et seq., 167); senegln 

 (the same) ; j?A;?/sa/«i (§ 167); syringin (§ 167); cesculin (§ 167); 

 Picrotoxin (§ 155); hellebore'tn (§ 167); cinchonine (is insoluble 

 in ether, §§ 171, 182, 184); theobromine (§ 177); papaverine 

 (§ 171); narceine (§ 171). Colchicine, sohmidl^ie, quebrachine, 

 geissospermine. 



§ 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 



