On the Manufacture of Crystals of Sulphate oflodo-qumine, 347 



The spirituous solution of iodine is made by dissolving 40 

 grains of iodine in 1 fluid ounce of rectified spirit of wine. 



I can after these explanations give the formula. 



Take of disulphate of quinine 50 grains, 



pyroligneous acid 2 fluid ounces, 

 proof-spirit 2 fluid ounces, 

 spirituous solution of iodine 50 drops; 

 dissolve the disulphate of quinine in the pyroligneous acid mixed 

 with the spirit ; warm the solution to 130° F., and directly add 

 the solution of iodine by drops, agitating the mixture from time 

 to time. 



This formula gives to the mother-liquid, after crystallization 

 at 52° F., a specific gravity of 0*986, which appears highly 

 favourable to the deposition of the majority of the crystalline 

 production, and yet allows only the very broad and thinner 

 plates to float — thus getting them perfectly free from all inter- 

 fering and adhering plates. 



It is necessary to perform this operation in a wide-mouthed 

 Florence flask or matrass, and to take care that the temperature 

 is maintained for a little time after the addition of the iodine, so 

 that the solution should become perfectly clear, dark, sherry-wine 

 colour ; then set it aside to crystallize under the following con- 

 ditions : — 



1st. It is essential that the apartment should be tolerably 

 equable in temperature, about 45° or 50° F., as a slight varia- 

 tion in the temperature produces currents in the crystallizing 

 fluid which destroy the parallelism of the crystals, and of course 

 negative all the efficiency of the manufacture ; and a greater rise, 

 if only to 60° F., redissolves the thinner plates. 



2nd. It is equally necessary that the liquid should be kept in 

 a perfect state of repose during the whole act of crystallization — 

 even the common vibration of the apartment must be counter- 

 acted, for the same important reason as the last. 



The best method to adopt is one which my friend Mr. John 

 Thwaites employs, namely, to suspend the flask by the neck 

 with strong twine, and attach this to a similar string stretching 

 across from one wall of the apartment to the other. This cer- 

 tainly gives the most uniform results, and offers other advan- 

 tages. 



The plan I had usually employed was to set aside the flask on 

 the steadiest support to be found, a wall, pillar or table ; and 

 imbed it on a feather, cotton, or tow pillow, to act as a non- 

 conductor and at the same time destroy vibration. 



3rd. It is also necessary that the surface of the fluid should 

 not be exposed to too rapid evaporation, as the temperature 

 would fall too quickly, and various currents and intestinal mo- 



2A2 



