immediately tinged brown, while the chloride assumes at first a violet hue.
The bromides, in solution, are readily decomposed and chloride being set free,
colors the liquid brown.

In the whole range of heliographic chemicals there is probably
not another collection less understood and being so productive
of interesting investigation as the bromides.

Bromide of Iodine.--M. de Valicours furnishes us with the best
method for preparing this mixture:

"Into a bottle of the capacity of about two ounces, pour thirty or forty drops
of bromine, the precise quantity not being of importance. Then add, grain
by grain, as much iodine as the bromine will dissolve till quite saturated.
This point is ascertained when some grains of the iodine remain undissolved.
They may remain in the bottle, as they will not interfere with the success
of the preparation.

"The bromide of iodine thus prepared, from its occupying so small a space,
can very easily be carried, but in this state it is much too concentrated
to be used. When it is to be employed, pour a small quantity,
say fifteen drops, by means of a dropping-tube, into a bottle
containing about half an ounce of filtered river water.
It will easily be understood that the bromide of iodine can be
used with a greater or less quantity of water without altering
the proportion which exists between the bromine and iodine."

This article forms a very good dry accelerator, and is by some persons
thought superior to all others, as it works with great uniformity,
and is less liable to scum the plate in coating at high temperatures,