Dr. Herapath on the Cinchona Alkaloids. 219 



filled with the solution, is absolutely impervious to light. It is pro- 

 bable that some molecular change is produced by the action of boil- 

 ing, even if only for a short time ; therefore it was necessary to make 

 a concentrated solution at 1 20° F., and set in repose for some days 

 at 62° F., by which precaution the solution experienced only a very 

 slight discoloration. When formerly experimenting on /3-quinidine, 

 the author obtained an iodo-sulphate very different from that which 

 he has described as indicative of the quinidine of Pasteur : having 

 pursued this inquiry, he is now enabled to state that his former dis- 

 crepancies arose from the fact that quinidine forms two iodo-sul- 

 phates, according to the manner in which it is treated. 



1st. When a dilute solution of the acid sulphate of quinidine is 

 mixed with one-third or one-half its bulk of rectified spirit and raised 

 to 160° or 180°, then treated with tincture of iodine in small quan- 

 tities, the red iodo-sulphate is produced, having the characters pre- 

 viously described as indicative of quinidine, — quinine, when similarly 

 treated, invariably producing the optical salt. 



The only precaution necessary to be taken in the case of the 

 alkaloid quinidine is to avoid adding an excess of iodine ; other- 

 wise an amorphous resinoid substance is deposited which will not 

 crystallize. 



2ndly. But when we treat the acid sulphate of quinidine in a con- 

 centrated form, diluted with from thirty to forty times its bulk of rec- 

 tified spirit at a temperature rather below 120° F., with the tincture 

 of iodine, even in greater proportions, an optical salt of quinidine is 

 produced, being the perfect analogue of the quinine salt. 



It crystallizes from this strong spirituous solution in acicular long 

 lanceolate prisms, the form of which appears to be a rhomboid having 

 30° for the acute and 150° as the obtuse angles ; but they are more 

 frequently found with a termination like the blade of an ordi- 

 nary bleeding-lancet. These prisms have a frequent disposition to 

 hemitropism, but in superposition, so that two plates may be often 

 found overlying each other in a parallel jjosition, wholly obstructing 

 light in those portions where thexj cover each other, but transmitting 

 an olive- or yellowish-green tint where separate. 



Sometimes the terminal planes are rectangular. This imbricated 

 mode of crystallization is very peculiar ; and although the author has 

 made thousands of experiments with quinine, yet he never saw any- 

 thing similar to it ; for this alkaloid invariably crystaUizes from dilute 

 alcoholic solutions as the a-prism, obstructing light when the length 

 is perpendicular to the plane of reflected light polarized in a vertical 

 plane, — or from strong alcoholic solutions, where the spirit is about 

 two-thirds the bulk, as /3-prisms, which obstruct light in the opposite 

 plane, or, as the author has described it, when the planes of their 

 length " lie in a plane parallel to that of the polarized beam with 

 which they are examined." In the case of quinine, these two sets of 

 prisms never occur together ; but if made by sej)arate operations 

 anil then urlijicially mixed on the same slide, they present the optical 

 characters of this new quinidine salt, viz. obstructing light luhen two 

 long prisms overlie each other in ajiarallel jiosition. They are there- 



Q2 



