§ 174. ESTIMATION OF STRYCHNINE, ETC. 183 



excess of potassio-mercuric iodide, dissolving the precipitate in 

 alcohol of 90 to 95 per cent., evaporating the filtered solution, and 

 weighing the residue, which contains 40*9 per cent, of atropine. 



For hyoscyamine the same precautions are necessary as for 

 atropine.^ 



In estimating coniine gravimetrically with potassio-mercuric 

 iodide, I obtained results that were far below the truth ; the 

 compound precipitated is somewhat freely soluble. (See also 

 §§ 175, 180.) 



Nux Vomica and St. Ignatius' beans contain two alkaloids, 

 strychnine and brucine, which differ in the intensity, at least, of 

 their action on animals, and this fact must not be lost sight of in 

 determining the value of those drugs by titration with potassio- 

 mercuric iodide. I have therefore proposed the following indirect 

 method of determining both alkaloids : ^ 



15 to 30 grams of the finely rasped seeds are exhausted by boil- 

 ing three times in succession with dilute sulphuric acid (1 in 50), 

 pressing the residue each time. The decoctions are united (about 

 700 cc), nearly (but not quite) neutralized with magnesia and 

 evaporated to a syrup in the water-bath. To the residue 2*4 

 times its volume of 90 per cent, spirit is added, and after 

 standing, the precipitated mucilage is filtered ofi" and washed. 

 The filtrate and washings are evaporated to about 30 to 50 cc. 

 and, whilst still acid, well shaken with chloroform. The chloro- 

 form is then separated, the aqueous liquid made alkaline Avith 

 ammonia, and the agitation with chloroform repeated as long as 

 any alkaloid is removed. The alkaloidal residue obtained by 

 evaporating the chloroformic solution is dried, weighed and dis- 

 solved in hydrochloric acid ; the excess of acid is removed by eva- 

 poration, and the solution titrated with potassio-mercuric iodide. 

 The weight of strychnine can be calculated from the expression 

 a; = 5-566 (0-0197 xc-w) and that of brucine from ?/ = 6-566 

 (m — 0-0137 X c), where c is the number of cc. of reagent used and 

 m the weight of the mixed alkaloids. It is still better to weigh 

 the hydrochlorates of the alkaloids and calculate the strychnine 

 salt from the expression x= 6-1733 (0-02152 x c-wi), and the 



^ Compare my ' Werthbestimmung,' 32, and Thorey on the ' Distribution of 

 Nitrogen in black and white henbane,' Diss. Dorpat, 1869, and Pharm. 

 Zeitschr. f. Russland, '265, 333, 1865 (Pharm. Journ. and Trans. [3], xii. 874). 



^ See my 'Werthbestimmung,' 64. Compare also Pharm. Zeitschr. f. Russ- 

 land, 233, 1866. 



