1 March 1882, the Edinburgh Photographic Society Meeting was described
as being unusually large, and terminating at a late hour. The
final event of the Meeting was a report from James Good Tunny who had
been given two bottles and asked to investigate their photographic
solutions are sent out, I understand for strengthening or giving density
1 is an old friend (or rather, I should say, an old enemy) under a new
name. It is a mercuric iodide in an excess of potassic iodide.
shall put a little of the solution into this test tube. I add a
few drops of bichloride of mercury, and now you see the bright scarlet
colour of iodide of mercury.
the other test tube I shall put a little of the No 1 solution, and now
add a few drops of nitrate of silver; there you see the yellow
precipitate of iodide of silver. This then is the active principle
of the bottle No 1.
bottle contains cyanide of silver. In order to prove so, I shall
place in this tube a small quantity of it. A drop or two of
muriatic acid added instantly forms a curdy precipitate of chloride of
the other tube I shall add to the No 2 solution a few drops of nitrate
of silver. This you will see instantly forms a heavy precipitate
of cyanurate of silver. This is exactly the solution that
Monckhoven, more than two years ago, gave to the public for the
intensifying of negatives.
who wish to make these solutions for themselves will find the following
formulae answer admirably:
bichloride of mercury: 20 grains
iodide of potassium: 60 grains
grind up these in a mortar with a few drops of water
30 grains of nitrate of silver dissolved in 2 ounces of water
60 grains of cyanide of potassium dissolved in 2 ounces of water
when dissolved, add the two together
filter into a 20 ounce bottle and fill up with water.
for my own working I prefer bromide of potassium instead of the iodide
that is used in No 1 solution using 30 grains of bromide instead of 60
grains of iodide.
conclusion: the note of warning cannot be too often sounded.
Beware of using mercury in any form for the strengthening of
negatives; many valuable ones have been lost by it. It is a
powerful and valuable agent.
I have subjected all intensified negatives by it to a bath of saturated
sulphate of iron. So far as these have been tested there seems to
have been little change after an exposure of some weeks to the little
sun that has been available recently.