CERTAIN ALKALOIDAL PERIODIDES. 265 



The amount of free iodine in the reagent was determined by titration with 

 thiosulphate and the total iodine by reduction with zinc dust and the precipita- 

 tion of silver iodide in the resulting colorless solution. The alkaloid was pre- 

 cipitated in acid solution in the usual manner and after equilibrium had been 

 established was filtered rapidly. The additive iodine of the precipitate was found 

 by solution in alcohol and titration with thiosulphate and the amounts of free 

 and bound iodine expended in the formation in the periodide estimated by the 

 determination of the residual free and total iodine in aliquot portions of the 

 filtrate. These experiments were carried out with two different reagents and 

 the conditions of the tests were varied in several ways. The following experi- 

 ments will serve to indicate the nature of the results obtained : 



Experiment A: 



Volume of solution, cubic centimeters 500 

 Morphine, grams 0.050 



Free iodine, grams 0.6114 



Total iodine, grams ' 1.2310 



Free H^SO^, grams 0.25 



Free iodine in filtrate, grams 



0.4721 



Total iodine in filtrate, grams 



1.0670 



Free iodine in precipitate, grams 



0.0980 



Experiment B: 





Volume of solution, cubic centimeters 



500 



Heroin, grams 



0.0568 



Free iodine, grams 



0.6114 



Total iodine, grams 



1.231 



Free HoSOj, gi-ams 



0.25 



Free iodine in filtrate, grams 



0.4793 



Total iodine in filtrate, grams 



1.0978 



Free iodine in precipitate, grams 



0.0860 



Experiment C: 





Volmne of solution, cubic centimeters 



500 



Heroin present, grams 



0.0568 



Free iodine present, grams 



1.2227 



Total iodine present, grams 



2.461 



Free H2SO4, grams 



0.25 



Free iodine in filtrate, grams 1.097 



Total iodine in filtrate, grams 2.311 



Free iodine in precipitate, grams 0.1005 



In general the results obtained were very variable and of somewhat questionable 

 value. The amoimt of "boimd" iodine or potassium iodide expended in the reac- 

 tion seldom corresponded to the amount demanded by theory and in a number of 

 experiments was apparently negative in value, a condition which was taken to 

 indicate that precipitation was incomplete and that compounds of iodine and 

 alkaloid existed in the filtrate. These experiments have been cited mainly because 

 they substantiate the claim that the free iodine of the reagent used up in the 

 precipitation can not again be wholly recovered by titration with thiosulphate. 

 In every experiment considerably more free iodine was present in the original 

 solution than was subsequently found in the titration of the filtrate and dis- 

 solved precipitate, the magnitude of the difference amounting to between two and 

 three atoms of iodine per molecule of alkaloid in the majority of cases. 



