I 
•8 
iodine and 1.5 per cent of potassium iodide) added gradually, the 
whole well shaken after each addition until further addition of the 
reagent produces no further precipitate, when the contents are 
diluted to 100 cc. and again well shaken. After the precipitate has 
settled thorouglily the licjuid is filtered, 50 cc. of the red filtrate 
decolorized by the gradual addition of 10 per cent sodium thiosul- 
phate, a few drops of phenolphthaleui added, and the excess of acid 
titrated with X/20 potassium hydroxide. It is found that 1 cc. of 
the acid is removed by 0.0137 gm. of morphme, from which the 
proper calculation will show the percentage of alkaloid in the speci- 
men examined. This method is, of course, quite simple, and the 
possibility of using phenolphthalein as the indicator is an advan- 
tage hardly to be overestimated, and which advantage the author 
rightly considers so important as to bring it out in the title® of the 
communication in which the method is described. Unfortimately, 
however, it has been found that the amoimt of acid carried dovm by 
the precipitate formed on addition of flayer’s or Wagner’s reagent 
is not a true measure of the amount of alkaloid in the solution. 
Thus Kippenberger, ^ who has investigated Gordin’s method, states 
that his experiments show that the results obtained by this method, 
whether using Wagner’s or flayer’s reagent, are so profoundly in- 
fluenced by the proportion of free acid, as well as by that of the 
potassium iodide in the solution, that they are useless for cpiantitative 
purposes, being not only far too high, but also extremely irregidar. 
Likewise, Gordin’s suggestion that the acid should be standardized 
by a known cpiantity of morphine is also found by Kippenberger to 
be unserviceable, since ecpiivalent quantities of morphine and. strych- 
nine titrated under identical conditions gave widely different results. 
On the other hand, as early as 1887, Plugge showed that, in 
general, m solutions of the salts of the alkaloids the free acid can be 
determined by titration with litmus while the total quantity of acid 
(free and combined) by titrating with phenolphthalein as indicator; 
since the latter indicator is neutral toward most of the vegetable 
alkaloids, and hence the acid combined with the alkaloid as salt 
acts toward it as if it were free acid. In adopting such a plan to 
the estimation of the free alkaloids, however, as is done by Barthe,^ 
the advantage in the use of phenolphthalein is lost, since the result 
obtamed is necessarily dependent on the accuracy with which the 
litmus indicator wiU show the actual amount of acid in excess of 
that which is combined with the alkaloid; and, in fact, the use of 
o The title of Gordin’s paper is; Simple Alkalimetric Method for the Estimation of 
Salt-forming Alkaloids with the Aid of Phenolphthalein as Indicator. 
&Zeit. anal. Chem., 42, 101-108 (1903). 
(“Arch. Pharm. (3), 25 , 45-49 (1887). 
d Compt. Pend., 115 , 512-514 (1892y 
