Silver nitrate 2 parts
Distilled water 100 parts
Nitrate acid, C.P. a trace
When the image is intense enough it is washed in several changes of water,
then toned in a solution of gold at 1 per 1,000 of water acidified with
traces of hydrochloride acid.(41)
The following bath develops slowly, and gives very rich purple tones
without toning:
Nitrate of silver 3 parts
Nitrate of uranium 1 part
Nitrate of cadmium 1 part
Alcohol 10 parts
Water 100 parts
Nitric acid traces
_The developing solutions should be as little acid as possible, but not
neutral, for then the proofs would be veiled and grayish._
The image can also be developed in a solution of gold, or in a very weak
solution of mercuric chloride at 1 per 10,000. The proof must be
extremely well printed and left for from two to five minutes in the
mercuric solution. If the time of exposure is right, the image will
change but little in the solution, and will take, when treated with silver
nitrate, the most splendid tones.
The proofs should be carefully washed when finished. If they were
developed with silver, they must be immersed in diluted aqueous ammonia,
which will perfectly clear the whites. If developed with chloride of
gold, the water should be heated to 60 to 80 deg. C. (140 to 176 deg.
Fahr.)