MICRO-ANALYSIS. 



847 



center than at the edges and are bounded by oscillatory com- 

 binations of the clinopinacoid with a prism and a clinodome 

 respectively. 



Optical properties : The extinction angle measured from the c 

 axis is 36 in the obtuse angle, and this direction is that of least 

 refractive index for the expect given. No definite interference 

 figure is observed on the clinopinacoid, and the axial plane is 

 therefore apparently parallel to this form. If this is the case 

 the optical orientation is fl Ac =-^ 36 in the obtuse angle ; ll = 6; 

 CAa= i6i in the acute angle. 



Fig. 341. Scopolamine hydrobromide : crystal aggregates from an alcoholic solution. 



Quinine Sulphate [(QoH^.N^OJo-H.SO, + 7H,0]. 



Occurrence: See p. 519. 



The alkaloid quinine (C20H04N0O2) is the methoxy-derivative 

 of cinchonine and separates in anhydrous crystals from hot aque- 

 ous solutions. If the hot solution, in dilute alcohol, is kept for 

 some time at 30 C, then on cooling long silky needles form. 

 There is another modification, occurring as a flaky powder and 



