MICRO-ANALYSIS. 849 



acid sulphate or bisulphate contains seven molecules of water of 

 crystallization (QoH^,4N20^,.HoS04 -|- /H.O), is also official, and 

 has been described.'^' (4) There is also a tetrasulphate of 

 quinine having the formula (Q0H20N2O0.2H0SO4 -|- 7H20).f 



At 25 C. one part of quinine sulphate (containing SH.O) is 

 soluble in 720 parts of water ; 86 parts of alcohol ; 400 parts of 

 chloroform. It is readily soluble in a mixture of chloroform 

 (2 parts) and absolute alcohol (i part) ; and one part is soluble 

 in 36 parts of glycerin at 25 C. It is only sparingly soluble in 

 ether. When crystallized from a dilute alcoholic solution, upon 

 a microscopical slide, the individual needles may attain a length 

 of 4 mm. (Fig. 226). 



(C,oH2nNoOo)o.HoS04 + SH.O. Crystals from aqueous solu- 

 tion. 



Orthorhombic. 



Forms observed: The three pinacoids : (100), (010) and 

 (001). 



Cleavage parallel to (100) and (010). 



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

 cr}'stals which are commonly needle-like with square terminations. 



Optical properties: a = c; \y = h; t^=a. An interference 

 figure is observed on the base, showing that the axial plane is the 

 brachypinacoid and that 2E is large. 



Salicin (CigHigO^). 



Occurrence : See p. 250. 



Salicin, through the action of ferments, yields saligenin and 

 glucose. I The crystals of commerce occur' in the form of prisms 

 or needles. At 25 C. one part of salicin is soluble in 21 parts 

 of water and 71 parts of alcohol. It is insoluble in ether 

 and chloroform. The individual crystals, which separate upon a 

 microscopic slide from alcoholic or aqueous solutions, vary in 

 length from 0.3 mm. to 5. mm. (see four-color plate). The 



*Th. HJortdahl, Zcitschr. f. Krystallog., 1879, 3, pp. 303, 304; see 

 also Hahn, Arch. d. Pharm., 1859, 99, p. 148. 



t Briihl, Die Pflanzen-Alkaloide, pp. 182, 183. 



t O. A. Oesterle, Grundriss der Pharmakochemie. 



54 



