832 BOTANY AND PHARMACOGNOSY. 



double salts/'- The crystals of cocaine hydrochloride and pal- 

 ladous chloride are prepared in the same manner as the caffeine 

 gold chloride, with the exception that to the solution containing 

 the cocaine hydrochloride a small quantity of hydrochloric acid 

 is added. To a few drops of this solution upon a slide are added 

 a few drops of the solution of palladous chloride, the two are 

 mixed by means of a glass rod and the slide is set aside to allow 

 the crystals to form. This frequently occurs almost immediately. 

 The individual crystals (Fig. 157, C^) vary in length from 0.3 mm. 

 to 1.6 mm. Skeleton crystals are also formed from .5 mm. to 

 6 mm. long (Fig. 157, D). 



Cocaine Hydrochloride and Palladous Chloride. 



Monoclinic ( ?) : a: b: c= ? (3 = 109. 



Forms observed : Clinopinacoid (010); orthopinacoid (100); 

 and base (001). 



Angles: Angle iooAooi=7i (normals). 



Habit : Tabular on the clinopinacoid and elongated along the 

 c axis, the usual ratio of length to width being 10: i or over. 



Twins. (a) Twinning plane the orthopinacoid and com- 

 position face the same plane (gypsum type), (b) Twinning 

 plane the orthopinacoid and composition face the clinopinacoid 

 (Carlsbad type). The occurrence of the latter type of twinning 

 is assumed largely for optical reasons as is noted below. 



The crystals have a strong tendency to fonn radiating aggre- 

 gates (Fig. 157, C) , and skeleton crystals (Fig. 157. D), due 

 no doubt to the fact that the substance is only slightly soluble 

 and the crystals therefore form rapidly. 



Optical properties: The extinction direction is 20 from the 

 long dimension of the crystal and lies in the acute angle ; this 

 direction is that of least refractive index. The orientation is 

 therefore : fl A c = 20 in the acute angle ; C A a = 39 in the 

 obtuse angle. f 



* W. Lessen, Ann. Chem. Pharm., 1865, 133, p. 355 : and Howard 

 and Stephenson, Proc. A. O. A. C, Nov., 1908, printed in Bulletin No. 

 122, pp. 97-100, of Bureau of Chemistry, U. S. Department of Agriculture. 



t See footnote (*) on p. 828. 



