NOTES AND ABSTRACTS IN CHEMISTRY AND PHARMACY. 357 
not permitted in journals to give their ideas on the subject, and old routine or 
error holds sway. I he public are much guided by the ‘ Pharmaceutical Journal’ 
in things of pharmacy; chlorodyne in every shape is valuable, but one kind as 
to coi tain symptoms differs as much from the others, as crude opium from prussic 
acid, if not more. 1 
Sack vide Street, November 14 th. 
I am, etc., 
Charles Kidd, 
M.D. 
NOTES AND ABSTRACTS IN CHEMISTRY AND PHARMACY. 
BY C. H. WOOD, F.C.S. 
The Purification of Bromide of Potassium. 
MM. Robiere et Herbelin have been engaged in examining a number of sam¬ 
ples of bromide of potassium for iodine. The test they employ is to place several 
fragments of the bromide, moistened with water, upon a piece of glazed paper, 
and expose to a trace of bromine vapour. If iodine be present, the paper ac¬ 
quires a blue tint. The bromine vapour is poured from a little flask filled with 
asbestos, wetted with bromine water. When the quantity of iodine is great, 
the blue tint may be partially or completely masked by the brown tint of free 
iodine, lo avoid tins, the test may be modified as follows. A crystal of the 
bioroide is pulverized and put in a watch-glass standing on a plate. A few 
drops of bromine are poured on the plate and the whole covered with a <dass. 
I he bromide is unchanged, if it is pure ; or if it takes a slight yellow tint, it loses 
it very rapidly in the air. If it contains a sensible quantity of iodine, it becomes 
immediately brown, the iodiue being displaced by the vapour of bromine. If it 
contains only minute traces of iodiue insufficient to give a visible coloration 
the salt is transferred to a corked tube and agitated with benzol. The liquid 
immediately assumes a rose tint easy to recognize. 
To puiify bromide of potassium completely from iodine, the authors recom¬ 
mend to dissolve the salt in a small quantity of water, and then add, little by 
little, bromine water to the solution, heated to boiling, uutil it is present in ex- 
cess. I he liquid is then boiled and evaporated to dryness with constant stirring 
The bromide is thereby perfectly deprived of iodine.” It is then crystallized. 
It has been since pointed out that, in the foregoing tests for detecting traces 
of iodine, the results may in every case be masked by the presence of any excess 
of free bromine. M. Duingt writes that if we introduce a little chloroform (or 
benzol or sulphide of carbon) into a solution of bromide of potassium contain- 
lu £ ToVofh P ar f of iodide, and then add drop by drop, shaking after each addi¬ 
tion, some dilute bromine water, we see the chloroform at first assume a violet 
tmt, become decolorized by the next addition, and ultimately take a yellow 
colour when an excess has been employed. At this point, if the cliloroformic 
l quid be decanted, and treated drop by drop with diluted sulphurous acid, it 
will reassume its violet colour. He recommends, therefore, that in testing 
bromide of potassium, after agitating a solution of the suspected salt with 
chloroform and some drops of bromine water, if no violet colour has been ob¬ 
tained, the chloroform should be separated and shaken with dilute sulphurous 
acid, added drop by drop, in order to restore the violet colour of the iodine if 
it is present. 
Method of Preserving' Drugs perfectly Dry. 
M. A. Melsens directs attention to the circumstance that dried leaves, roots, 
