_New Developing Fluid._--DR. DIAMOND has reported very favourably of the
developing fluid, which I spoke of in "N. & Q." of March 12 as "being
simple, inexpensive, and keeping good a length of time." In accordance with
what I then stated, I herewith give the readers of "N. & Q." the benefit of
it, and leave them to form their own opinion of its value after trying it:
Protosulphate of iron 12 grs.
Nitrate of lead 8 grs.
Water 10 drs.
Acetic acid ½ dr.
Dissolve the protosulphate of iron in the water; then throw in the nitrate
of lead in powder; stir with glass rod until it is dissolved; keep stirring
while pouring in the acetic acid, and for a few minutes afterwards. Let the
precipitate subside, then filter. I have used nothing else for positives on
glass since I discovered the preparation. I have not tried it for
developing in the wax-paper or other paper process. The liquid is
colourless as water when first made. By long keeping it will change colour,
but throws down no deposit, nor loses its properties. If those gentlemen
who try it would give their opinions of it, I should be obliged.