MICRO-ANALYSIS. 827 



as being di-methoxy-strychnine. If crystallized from hot water 

 it contains 4 molecules of water of crystallization, but when 

 crystallized from alcoholic solutions it contains but two molecules,* 

 A number of salts are used in medicine and the sulphate alone 

 was examined. The crystals of brucine sulphate vary in length 

 from I to 2.5 mm. (Fig. 331). 



Brucine Sulphate. Crystals from saturated aqueous solu- 

 tion. 



Orthorhombic : a: b: c =^ 0.8329 : i : c. 



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

 unit prism (no). 



Angles: Angle no A iio= 79 35^ Cleavages parallel to 

 the unit prism and base. 



Habit : Tabular on the base ; the crystal elongated along 

 the a axis, bounded by the brachypinacoid and unit prism (Fig. 

 331). In some cases the pyramid (nc) replaces the prism, or 

 at least truncates the prism base edge. The base is often replaced 

 by a series of flat brachydomes so that a cross-section of the 

 crystal parallel to the macropinacoid is lens-shaped. 



Optical properties : SL^^a; \X =^c; t=^b. Axial plane the base 

 (001). Bxa'=h; optical sign 4-. 2^ = large. An interference 

 figure is visible on the brachypinacoid. 



Caffeine (CgH^oN^O. -f- H.O). 



Occurrence : See pp. 435, 436. 



Caffeine (theine, or trimethyl-xanthine), while it can be 

 produced synthetically, is usually prepared from tea and tea dust 

 or sweepings. If crystallized from aqueous solutions it con- 

 tains one molecule of water of crystallization which is wanting 

 if it is crystallized from alcohol, chloroform or ether. The 

 crystals from aqueous solutions may attain a length of 20 mm. 



At 25 C. one part of caffeine is soluble in 45.6 parts of 

 water; 53.2 parts of alcohol; 375 parts of ether; and 8 parts 

 of chloroform. 



Caffeine. Crystals from aqueous solutions. 

 * O. A. Oesterle, Grundriss der Pharmakochemie. 



