MICRO-ANALYSIS. 833 



Certain crystals have no definite extinction, but show a direc- 

 tion of minimum illumination at 15 or less from the long direc- 

 tion of the crystal. This might be explained by the Carlsbad 

 twinning, referred to above, which explanation is rendered more 

 probable by the fact that the position of minimum illumination 

 in such crystals varies in different parts. The fact that such 

 crystals show a strong double refraction would preclude the possi- 

 bility of their being in such a position that an optic axis is nearly 

 vertical. 



Pleochroism: a=pale yellow. 



C reddish-yellow. 



An interference figure was not obtained. 



Codeine Sulphate [ (Ci8H,,N03),.H,SO, -f sH.O]. 



Occurrence : See p. 659. 



Codeine (the methyl ether of morphine) forms anhydrous 

 crystals from solutions in ether or benzol but the crystals from 

 aqueous solutions contain one molecule of water of crystalliza- 

 tion.* Microscopic x-shaped skeleton crystals separate from 

 alcoholic solutions which vary in length from about 50 /* to 100 [x 

 (Fig. S3~^- It forms crystallizable salts, of which the sulphate 

 only will be described. At 25 C. one part of codeine sulphate is 

 soluble in 30 parts of water, and 1035 parts of alcohol. It is 

 insoluble in chloroform or ether. The microscopic crystals from 

 hot alcoholic solutions vary in length from 0.3 mm. to 2.5 mm. 

 (Fig. 333)- 



Codeine Sulphate. Crystals from alcoholic solution. 



Orthorhombic : a: b: c ^ 0.288 : i : 0.419. 



Forms observed: Macropinacoid (100); base (001); unit 

 prism (no) ; brachydome (on) ; and brachypinacoid (010) (?). 



Angles: Angle iioA 110 = 32 approximately; oiiAoIi = 

 45 30^ 



* Oesterle, Pharmakochemie, p. loi ; and Briihl, Die Pflanzen-Alkaloide, 

 P- 341- 



53 



