23,i Cole: Potassium Ferrocyanide 99 



/3-EUCAINE 



Sensitivity, 1 : 200. 



/?-eucaine forms with potassium ferrocyanide in hydrochloric 

 acid solution colorless, thin, elongated, hexagonal or rhombic 

 plates. They tend to grow to a very large size but they remain 

 very thin. Under crossed nicols they are weakly polarized, ex- 

 hibiting parallel and symmetrical extinction. Scratching of the 

 preparation to induce crystallization is necessary. Plate 1, 

 fig. 1. 



BRUCINE 



Sensitivity, 1 : 2,500. 



Brucine forms with potassium ferrocyanide in hydrochloric 

 acid solution highly refractive, stocky prisms with chisel-shaped 

 ends. Usually the prisms occur in rosettes. Under crossed 

 nicols the crystals are strongly polarized, exhibiting parallel 

 extinction. There is a tendency toward supersaturation, and 

 scratching of the preparation is necessary. Plate 1, fig. 2. 



CINCHONIDINE 



Sensitivity, 1 : 300. 



Cinchonidine in hydrochloric acid solution yields with potas- 

 sium ferrocyanide rosettes of yellow, curving, hairlike needles 

 (Plate 1, fig. 3) when the concentration of the alkaloid is over 

 0.5 per cent. At 1 : 300 long thin rectangular yellow plates, 

 exhibiting parallel extinction under crossed nicols, form near 

 the edge of the drop. Scratching or seeding aid in the crystal 

 formation. 



CINCHONINE 



Sensitivity, 1 : 1,000. 



Cinchonine forms with potassium ferrocyanide in hydrochloric 

 acid solution yellow, irregular, trapesium-shaped crystals, often 

 grouping in the form of rosettes. They polarize strongly. Cin- 

 chonine is readily distinguished from cinchonidine and quinine 

 by this test. Quinine does not yield a crystalline precipitate, 

 and cinchonidine yields either hairlike crystals or thin rectan- 

 gular plates. Plate 1, fig. 4. 



COCAINE 



Sensitivity, 1 : 500. 



Cocaine forms with potassium ferrocyanide in hydrochloric 

 acid solution colorless, six-sided plates and prisms of irregular 

 shape. They polarize strongly under crossed nicols. On edge 



