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XXVII. On the Chemical Constitution and Atomic Weight of the 

 new Polarizing Crystals produced from Quinine. By William 

 Bird Herapath, M.D.*^ 



IN the March Number of this Journal the author announced 

 the discovery of a peculiar salt of quinine, which possessed 

 the power of polarizing a ray of light with even greater inten- 

 sity than the tourmaline ; and at certain angles of rotation it also 

 depolarized light, and acted as selenite would do under similar 

 circumstances. 



He then stated that the qualitative analysis showed this salt 

 to be a compound of quinine, iodine, and sulphuric acid ; and 

 although the relative quantities of these constituents had not at 

 that time been estimated, he gave it the name of iodide of di- 

 sulphate of quinine. In the present communication, the results 

 of the quantitative chemical analysis of this compound will be 

 detailed ; and it will l)e evident that a new idea of its constitu- 

 tion will be elicited, which will render another name necessary, 

 and more in accordance with the results specified. 



Before attempting the analysis, it was of course necessary to 

 invent a process which would furnish a large quantity of this 

 substance at one operation ; after several attempts, with more or 

 less success, the following method was adopted, which at the 

 same time served as a means of corroborating the results of the 

 future analysis, as it enabled the experimenter to account for all 

 the iodine used in the operation. 



A tubulated retort was adapted to a receiver by careful con- 

 nections, and the latter adjusted to a second receiver, somewhat 

 in the manner of a Wolff's apparatus ; the condensers were then 

 surrounded by a freezing mixture of nitre and hydrochlorate of 

 ammonia. Into the retort were placed 100 grs. of pure disul- 

 phate of quinine, 3 fluid ounces of pyroligneous acid, 2 drms. 

 of diluted sulphuric acid (containing about 12 grs. of dry acid) ; 

 when this mixture had been raised to about 180° Fahr., the al- 

 coholic solution of iodine was gradually added through a bent 

 glass funnel adapted to the tubule of the retort. In this man- 

 ner 30 grs. of iodine dissolved in 1150 grs. of alcohol were em- 

 ployed ; the whole operation occupied about half an hour, during 

 which period a reddish-coloured fluid was collected in the re- 

 ceivers, about 4 fluid drachms in quantity ; this of coui'se was 

 carefully set aside for examination. 



The whole was allowed to grow cold, still in connection ; an 



abundant crop of ciystals formed in the retort, which, having 



been kept during twenty-four hours at a temperature of 40° 



Fahr. to deposit, were collected on a filter, and washed several 



* Communicated by the Author. 



