§§ 180, 181. SErAEATION BY PEECIPITATIOX. 189 



and distilled (finally at a temperature of 260'') into a measured 

 quantity of volumetric sulphuric acid, the excess of which is then 

 determined by solution of soda. Wittstein and Brandl distil the 

 a,cid extract direct with caustic potash, and note the amount of 

 sulphuric acid necessary to neutralize the distillate. They then 

 evaporate to dryness, extract with alcohol, which dissolves the 

 sulphate of nicotine, and determine the sulphuric acid in the 

 insoluble portion. This is then deducted from the quantity used, 

 and from the difference the nicotine present is calculated. 



Kosutany treats the leaves, previously soaked in water, with 

 milk of lime until free from ammonia, then extracts Avith water, 

 and shakes the filtered solution with petroleum spirit. From the 

 latter, after separation, the alkaloid is removed by agitating Avith 

 a known quantity of volumetric sulphuric acid, the excess of 

 which is determined by l)aryta water. (Compare my ' "Werthbe- 

 stimmung,' p. 55.) 



§ 180. Coniine. — Similar methods have also been proposed for 

 the estimation of coniine. I have already expressed my opinion 

 of them in my ' Werthl^estimmung,' p. 42, where I have at the 

 same time pointed out that those processes which involve the 

 evaporation of a solution of cliloride of coniine, and determination 

 of the alkaloid from the amount of chlorine in the residue, ^ are 

 open to objection on the ground that chloride of coniine is easily 

 volatihzed (^§ 174, 65). 



§ 181. Separation of tivo Alhaloids. — Attention has already heew 

 drawn in !^ 69 to cases of the occurrence of two alkaloids in 

 vegetable substances. The remarks made in that section may be 

 supplemented here with a few examples so taken as to include 

 details of processes of more freqiient applicability, and to give 

 hints for the A'aluation of drugs in general use. Some such 

 instances have already Ijeen described in i^ 174, and I propose 

 following these here Avith the discussion of a few more methods 

 for the separation of oidji itco alkaloids. 



Let us first assume that the two alkaloids to be separated differ 

 in their hehaviour to acids, as, for instance, jervine and rerafroidine, 

 alkaloids that occur in Veratrum album, lobelianum and viride.^ 



^ Compare Hager, ' Untersuchungen,' ii. 250. 



- See Tobien, ' Beitr. z. Kenntniss der Veratrum AlkaloiJe,' Diss. Dorpat, 

 1877 (Pharm. Journ. and Trans. [3], viii. 80S) ; Bullock, Amer. Journ. Pharm. 

 xlvii. 451, and xlix. 453 ; Wormley, ibid, xlviii. 4. 



