264 



HOLMES. 



Table VIII. — Experiments icith morphine sulphate under circumstances unfa- 

 vorable for periodide precipitation. 



Number 

 of experi- 



Grams 

 alkaloid. 



Volume 



of 

 solution. 



Alcohol 

 present. 



Free 

 acidity 

 grams 

 H0SO4. 



Yq iodine- 



Atoms 

 of iodine 

 per mole- 

 cule of 

 alkaloid. 



ment. 



Added. 



Used up. 









cc. 





cc. 



cc. 





68 



0.050 



200 



None. 



0.25 



3.00 



1.04 



0.59 



69 



0.050 



200 



None. 



None. 



3.00 



2.95 



1.68 



70 



0.050 



200 



10 



None. 



9.93 



4.92 



2.81 



71 



0.050 



200 



50 



None. 



10.02 



2.49 



1.42 



72 



0.050 



200 



100 



None. 



10.04 



0.91 



0.52 



In only one experiment, number 10, was any precipitate obtained, and 

 it was shown by a prolonged extraction of this with an excess of thiosul- 

 phate solution that of the total ana.ount of iodine which had been removed 

 from the "free" state slightly more than 65 per cent had remained in 

 the filtrate. In the other experiments in which the solutions remained 

 perfectly clear, varving amounts of free iodine were used up. The end 

 point was in every case perfectly distinct and it was plain that soluble 

 compounds of morphine and iodine had been formed. A check was 

 made on experiment number 69 by adding iodine solution, drop by drop, 

 to that of an alkaloidal solution which had been treated with starch and 

 diluted to nearly a volume of 200 cubic centimeters. The amount of 

 iodine which was required to give a permanent blue color corresponded 

 to the ratio of 1.64 atoms of iodine per molecule of morphine. Xo 

 precipitate was formed. 



This fact, that there are soluble compounds of iodine and morphine 

 which will not give up their free iodine upon titration with thiosul- 

 phate, is of the greatest importance. 



It would appear that a certain amount of the free iodine which 

 enters into combination with the base must be bound to it much more 

 intimately than would be the case if it were merely additive to the 

 hvdriodide radical, or it would otherwise react with the thiosulphate. 



Prescott and Gordin=^ have investigated the mechanism of the reaction of 

 atropine with Wagner's reagent and found that an amount of potassium iodide 

 is used up br the reaction equivalent to that required by theory for the forma- 

 tion of the hydroiodic acid group of the periodide. They did not attempt to show 

 that all the "free" iodine expended in the reaction was held in the "additive" 

 condition and could be recovered by titration with thiosulphate. 



In the course of the present work a number of similar experiments 

 were undertaken in order to throw light on nature of the reactions with 

 morphine and heroin. 



^Journ. Am. Chem. Soc. (1898), 20, 720. 



