Cole: Potassium Ferrocyanide 



Stovaine yields with potassium ferrocyanide in hydrochloric 

 acid solution rosettes of needles usually radiating from a solid 

 mass at the center. The individual crystals exhibit parallel ex- 

 tinction under crossed nicols. The crystals tend to form first 

 at the edge of the drop. Plate 2, fig. 11. 



.... . „««*« STRYCHNINE 



Sensitivity, 1 : 20,000. 



Potassium ferrocyanide affords a very sensitive test for strych- 

 nine. In hydrochloric acid solution this reagent yields with 

 strychnine long, slender needles, or spear-shaped crystals with 

 serrated edges (Plate 2, fig. 12). Hemimorphic triangular 

 plates are sometimes formed. Under crossed nicols the long 

 crystals exhibit oblique extinction. When the concentration of 

 the strychnine is high but very little reagent is added, the true 

 form of the compound sometimes comes out on scratching. 

 These are small rhombic plates exhibiting symmetrical extinc- 

 tion under crossed nicols. 



a ■*• -. , , nn VERATRINE 



Sensitivity, 1 : 100. 



The white amorphous precipitate obtained when potassium 

 ferrocyanide is added to a hydrochloric acid solution of veratrine 

 yields crystals only with great difficulty. The crystals formed 

 are imperfect and might not be recognized if polarized light 

 were not used. Under crossed nicols they polarize strongly. 

 The test, however, is not a satisfactory one. 



SUMMARY 



1. Thirteen of forty of the common alkaloids yield crystalline 

 precipitates with potassium ferrocyanide in hydrochloric acid 

 solution. These precipitates are sufficiently characteristic to be 

 used as corroborative identification tests. 



2. The tests can be applied to very minute amounts of ma- 

 terial. 



3. Potassium ferrocyanide is a satisfactory microchemical 

 reagent for the distinction of cinchonidine, cinchonine, and qui- 



4. Brucine and strychnine are readily distinguished by this 

 reagent. 



5. Cocaine can be distinguished from /S-eucaine, stovaine, and 

 heroine by the potassium ferrocyanide test. 



6. The sensitivity of the potassium ferrocyanide test for the 

 various alkaloids has been determined. 



