ON THE FORMATION OF CERTAIN ALKALOIDAL 



PERIODIDES— PRELIMINARY 



INVESTIGATION. 



By W. C. Holmes. 

 {From the Laboratory of Organic Chemistry, Bureau of Science, Manila, P. I.) 



I]SrTRODUCTIO^^. 



The systematic investigation of the periodides of the alkaloids was 

 begun in 1869 by Jorgensen.^ In 1887 Geuther ^ presented a general 

 re\dew of the subject and a classification of all the periodides then kno\\Ti. 

 More recently, classifications of the periodides of both organic and 

 inorganic bases, and of other perhalides have been made by A. B. Prescott^ 

 and M. Gomberg.* 



The quantitative determination of vegetable bases by the precipitation of their 

 periodides in aqueous solution was first attempted by R. Wagner* who employed 



an il aqueous solution of iodine and potassium iodide, since known as Wagner's 



reagent. A similar solution had already been adopted by Bouehardat.° Wagner 

 gave a list of organic bases which might be precipitated, and stated that caflfeine, 

 theobromine, piperine and urea gave no precipitates. A quantitative study was 

 made with the sulphates of quinine and cinchonine, showing that under approx- 

 imately similar conditions the alkaloids required a definite amount of iodine for 

 precipitation and that empirical factors could be established for the determina- 

 tion of such organic bases as gave insoluble periodides. 



In 1S8.5 Schweissinger ' found that the method gave good results with strych- 

 nine, even in the presence of free mineral acid or alcohol, but was unsatisfactory 

 with brucine. He recommended the addition of the iodine reagent in slight excess 

 to avoid high results, the rapid filtration of the solution and the minimization 

 of the volume of water employed in washing the precipitate to avoid as far as 

 possible any solution or decomposition of the periodide. 



^Journ. f. prakt. Chem. (1869), II, 2, 433. 

 -Ann. d. Chem. (Liebi) (1887), 240, 66. 

 ^ Journ. Am. Chem. Sac. (1895), 17, 775. 

 *Ibid. (1896), 18, 347. 

 ^ Ditigler's polytech. Journ. 161, 40. 



Ztschr. f. anal. Chem. (1862), 1, 102. 

 "Compt. rend. Acad. sci. (1839), 9, 435. 

 'Arch. d. Pharm. (1885), 223, 615. 



253 



