THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 

 MARCH 1852. 



XXVI. On the Optical Properties of a newly-discovered Salt of 

 Quinine, which crystalline substance possesses the power of po- 

 larizing a ray of Light, like Tourmaline, and at certain angles 

 of Rotation of depolarizing it, like Selenite. By William 

 Bird Herapath, M.D. London University, M.R.C.S. Engl., 

 Member of the Bristol Microscopical Society, fife* 

 [With a Plate.] 



SOME short time since my pupil called my attention to some 

 peculiarly brilliant emerald-green crystals, which had formed 

 by accident in a solution of the disulphate of quinine. He could 

 give me no account of their formation. Some experiments made 

 upon them convinced me of their importance, both chemically 

 and optically, and led me to suspect that iodine was in some way 

 necessaiy to their composition. 



Upon dropping tincture of iodine into the solution of disul- 

 phate of quinine in diluted sulphuric acid, an abundant deposi- 

 tion of similar crystals immediately occurred. However, it was 

 found exceedingly difficult to experiment in a satisfactory manner 

 upon the crystals thus formed, as it was almost impossible to 

 isolate them from their mother-liquid. It was subsequently 

 found, that by dissolving the disulphates of quinine and cincho- 

 nine of commerce in concentrated acetic acid, upon warming the 

 solution, and dropping into it a spirituous solution of iodine 

 carefully by small quantities at a time, and placing the mixture 

 aside fur some hours, large brilliant plates of" this substance were 

 produced. These could be readily separated from their mother- 

 liquid, and by frecment recrystallization, purified. 



The crystals of this s:dt, when examined by reflected light, 



* Communiouteil by the Author ; to whoso liberality we are likewise 

 indebted for the beautiful plate which accompanies this paper. 



1'hil. Mag. S. 4. Vol. 3. No. 17. March 1852. M 



