MICRO-ANALYSIS. 839 



parts of water; and at 60 C. one part is soluble in 17 parts 

 of alcohol.* When crystallized upon a microscopic slide from 

 alcoholic solutions the crystals of hydrastine vary in length from 

 0.1 mm. to 1.2 mm. (Fig". 336). 



Hydrastine. Crystals from alcoholic solution. 

 Orthorhombic : a: b: c ^ 0.8461 : i : 0.3761.! 

 Forms observed: Prisms (no) and (870); macrodome 

 (201). 



Angles: angle iioAtTo^8o 28' 

 87oA87o = 73 02' 

 201 A 201 = 83 16' 



Plane angle on (870) between the edges of (201) and (870) 

 (870-201 A 870-870) = 62 f. 



Habit: Crystals usually show a combination of prism (870) 

 and macrodome (201), flattened on one pair of the prism faces 

 (Fife- 33*^ ) The larger crystals are nearly equi dimensional ; 

 the smaller ones often being elongated on the c axis, with the 

 ratio of length to width of 3:1 or over. 



In the usual aspect, lying on one of the (870) prism faces, 

 the crystal appears as a flat plate bounded by six edges, making 

 angles with each other of approximately 120. If the length and 

 width are the same, this gives the appearance of a more or less 

 distorted hexagon. As may be seen from the above, however, 

 this hexagon is not regular Imt has two angles of 124 and four 

 angles of 118 (118 = i8o 62). The unit prism (no) is 

 of rare occurrence and is observed on the larger crystals. 



Optical properties : Owing to the habit it is difficult to 

 obtain a crystal in such a position that it would afford a view 

 along one of the bisectrices. However, it would seem from what 

 could be obtained, that the axial plane is the brachvpinacoid 

 (010), and Bx^ = a. In the usual aspect of the crystals on the 

 prism face, the c axis is the direction of greatest refractive 

 index. 



* A. Seidell, Solubilities of Inorganic and Organic Substances, 

 t E. A. Wi'ilfing, Zeitschr. f. Krystallog., 1888, 14, p. 99. 



