First make two stock solutions as follows:
No. 1. A saturated solution of oxalate of potash (a pint or quart)
and test with blue litmus paper. If it does not show an acid
reaction dissolve a little oxalic acid in water and add enough to
the solution to cause the blue test paper to turn red.
This solution should be filtered for use.
No. 2. Make a saturated solution of pure sulphate of iron, and to
one quart add three or five drops of sulphuric acid, to prevent
oxidation, and filter.
Now, to develop a 5x8 plate, take three ounces of No. 1 and to this
add one quarter of a dram of bromide of potassium solution (which is
water one ounce, bromide of potassium twelve grains), then add half
an ounce of No. 2; this forms the developer. [p175]
Then transfer the plate to a developing disk, and pour over it the
developer. If the picture comes out gradually and develops
sufficiently, it is good so far, but if from under-exposure the
details hang back and refuse to develop further, then add two drams,
or half an ounce, more of No. 2, which will bring out the picture
with full details, unless greatly under-exposed.
Never exceed one ounce of No. 2 (iron) to three ounces of No. 1
(potash), for if you do you will form a sandy deposit and
discontinue the action of the developer.
Always develop until the picture seems sunken into the surface. Do
not judge by looking through the negative only. Wash and fix in
hypo, 1 ounce; water, 8 to 10 ounces. After fixing, wash well.
For pictures taken instantaneously, use no bromide in the developer.