MICRO-ANALYSIS. 831 



Orthorhombic sphenoidal : a: b: c = 0.3294 : i : 0.9758.* 

 Forms observed: Base (001); macropinacoid (100); 

 brachypinacoid (010); macrodome (101); and prism (140). 



Angles: Angle 140 A 140 =105 36'. 



Habit: Tabular on the base, bounded by the brachypinacoid 

 and macropinacoid or macrodome, the elongation being in the 

 direction of the b axis, with a ratio of length to width of about 

 2 or 3: I. It is possible that the macropinacoid does not appear, 

 since it is difficult to distinguish between the macropinacoid and 

 the two faces on the macrodome in thin crystals. One or more 

 faces of the prism (140) are usually present, unsymmetrically 

 arranged. Interpenetrating twins on the prisms (470) and (130) 

 are observed, the angles between the longer axes being approxi- 

 mately 60 and 90 in the two cases respectively. 



Optical properties: a=c; h=b; t=a. The axial plane is the 

 brachypinacoid. Bxa=c. Optical sign - . An interference 

 figure is visible on the base. 



Cocaine Hydrochloride (C17H21NO4.HCI + 2H2O). Crys- 

 tals from aqueous solution. 



Orthorhombic : a: b: c ^ 0.894 : i : r. 



Forms observed: Base (001); brachypinacoid (010); 

 macropinacoid (100); and unit prism (no). 



Habit : Tabular on the base, elongated along the a axis, 

 the crystals being extremely thin but having considerable width. 

 In some cases, however, they become quite narrow and needle- 

 like ; this is often the case when radiating aggregates are formed. 

 (See four-color plate.) 



Optical properties: ^=a; 6=6; t=C. Axial plane the 

 macropinacoid. Bxa=c, Optical sign +. A very good inter- 

 ference figure is seen on the base and shows that 2E is not 

 very large, although the emergence of the optic axes was not 

 observed. 



Cocaine Hydrochloride and Palladous Chloride. 



Cocaine and cocaine hydrochloride give with a number of 

 reagents, including palladous chloride, characteristic crystalline 



* Valentin, Zeitschr. f. Krystallog., 1889, 15, p. 36. 



