CERTAIN ALKALOIDAL PERIODIDES. 



263 



Table VII. — Influence of temperature. 



MORPHINE. 



Number 

 of exper- 

 iment. 



Grams 

 alkaloid. 



Free 

 acidity, 



grams 

 H^SOi. 



Tempera- 

 ture. 



jq iodine— 



Atoms of 

 iodine 

 per mole- 

 cule of 



alkaloid. 



Added. 



Used up. 



62 

 63 



0. 03971 

 0. 03971 



0.25 

 0.25 





 30 



cc. 



14.96 



14.96 



cc. 



3.60 



1.64 



2.58 

 1.17 



CODEINE. 



64 



0.3894 



0.25 







14.96 



5.98 



65 



0.3894 



0.25 



30 



14.96 



4.72 



4.59 

 3.63 



HEROIN. 



67 



0.5088 

 0. 5088 



0.25 

 0.25 





 30 



14.96 

 14.96 



5.33 



5.07 



3.87 



3.68 



With all three alkaloids, the amount of iodine which enters into the 

 periodide varies directly with the absolute concentration of the solution 

 and inversely with a rise in temperature or an increase in the concen- 

 tration of sulphuric acid or potassium iodide in the solution. The 

 experiments also indicate that it is immaterial which solution is added 

 to the other in the precipitation and that equilibrium is reached in a 

 comparatively short period. Certain determinations not included in the 

 table showed that half an hour is sufficient, especially if the solution is 

 occasionally agitated. 



All of the codeine precipitates were plainly crystalline, and the 

 largest and best defined crystals were obtained in experiment number 36 

 under conditions of low absolute concentration. None of the heroin 

 precipitates appeared to crystallize and only two definitely crystalline 

 morphine compoimds were obtained, one in experiment number 31 with 

 a concentrated solution and the other in experiment number 62 at a low 

 temperature. 



According to the accepted theory of the use of Wagner's reagent, a 

 certain amount of free iodine enters into the alkaloidal periodide pre- 

 cipitate and this amount may be accurately determined by the titration 

 with thiosulphate of the free iodine remaining in the filtrate and sub- 

 tracting this residual free iodine from the amount known to have been 

 originally present. The following experiments will serve to demonstrate 

 the fallacy of this conclusion. 



