_Protonitrate of Iron_.--"Being in the habit of using protonitrate of iron
for developing collodion pictures, the following method of preparing that
solution suggested itself to me, which appears to possess great
advantages:--
Water 1 oz.
Protosulphate of iron 14 grs.
Nitrate of potash 10 grs.
Acetic acid ½ drm.
Nitric acid 2 drops.
In this mixture nitrate of potash is employed to convert the sulphate of
iron into nitrate in place of nitrate of baryta in Dr. Diamond's formula,
or nitrate of lead as recommended by Mr. Sisson; the advantage being that
no filtering is required, as the sulphate of potash (produced by the double
decomposition) is soluble in water, and does not interfere with the
developing qualities of the solution.
"The above gives the bright deposit of silver so much admired in Dr.
Diamond's pictures, and will be found to answer equally well either for
positives or negatives. If the nitric acid be omitted, we obtain the
effects of protonitrate of iron prepared in the usual way.--JOHN SPILLER."
(From the _Photographic Journal_.)
_Photographs in natural Colours_.--As "N. & Q." numbers among its
correspondents many residents in the United States, I hope you will permit
me to inquire through its columns whether there is really any foundation
for the very startling announcement, in Professor Hunt's _Photography_, of
Mr. Hill of New York having "obtained more than fifty pictures from nature
in all the beauty of native coloration," or whether the statement is, as I
conclude Professor Hunt is inclined to believe, one of those hoaxes in
which many of our transatlantic friends take so much delight.