_An iodizing Difficulty._--May I request the favour, from some one of your
numerous photographic correspondents, of a solution to the following
apparent enigma, through the medium of "N. & Q."?
Being located in a neighbourhood where there is a scarcity of water in the
summer months, I lately took advantage of a pool in a running stream, which
ran at the bottom of the grounds of a friend, to soak my calotype papers
in, subsequent to having brushed them over with the solution of iodide of
silver, according to the process recommended by SIR W. NEWTON. One-half of
the batch was removed in about two hours and a half, being beautifully
clean, and of a nice light primrose colour; and in consequence of an
unexpected call and detention longer than I had anticipated, the other half
was left floating from two o'clock P.M. until seven or eight in the evening
(nearly six hours), when, much to my chagrin, I found on their removal that
they had all, more or less, become browned, or, rather, had taken on a
dirty, deep, nankeen colour, those that had been first floated being
decidedly the worst. I had previously thought that the papers _must_ be
left _at least_ two and a half to three hours, a longer period having no
other effect than that of softening the papers, or, at most, of allowing
some slight portion of the iodide to fall off from their surface, whereas,
from the above-described discoloration, an evident decomposition must have
commenced, which I am quite at a loss to account for; neither can I
conjecture what the chemical change can have been. I have several times
before prepared good papers in trays filled with water from the same
stream, but from the quantity running in the brook in the spring months, I
never before have had the chance of floating them in the stream itself.
An explanation of the above difficulty from some obliging and
better-informed photographist would be very thankfully received by