With these three, compounds of great variety are formed.

The silver surface is first thoroughly cleaned and freed from all organic
matter, then exposed to vapor of iodine, producing an iodide of silver.
The plate upon which is this salt, is again exposed to the vapor of bromine,
forming a bromo-iodide of silver, a salt also.

As most of the various accelerators are compounds of bromine, with either
chlorine or fluorine combination, they partake somewhat of the nature of these
latter, giving results which can be detected by the experienced operator.
Thus muriatic acid is added for its chlorine, which can generally be
detected by the impression produced, being of a light, soft, mellow tone,
and in most cases presenting a brilliant black to that colored drapery.
Those who wish to experiment with agents for accelerating substances,
should first study to well understand their peculiar nature and properties;
as well, also, to endeavor to find out what will be the probable changes
they undergo in combination as an accelerator. This should be done before
making the experiments. From the foregoing it will be seen that numerous
compounds are formed from the same basis, and, consequently, it would
be a waste of time and a useless appropriation to devote more of our space
than is necessary to give the principal and most reliable combination.

In America, the words "Quick" and "Quick Stuff," are more generally used for
and instead of the more proper names, "Sensitives," or "Accelerators," etc.
As it has by use become common, I frequently use it in this work.

Liquid Accelerator, No. 1.--This mixture was used by me in 1849,
and is given as it appeared in my "System of Photography,"
published at the above date: