ferrocyanate

One of these trays should contain a layer, about three-quarters of an inch thick, of an almost saturated solution of potassium ferrocyanate (the developer); the next be filled with water, and the third with water acidified by sulphuric acid in the proportion of three per cent. in volumes.

Photographic Reproduction Processes Peter C. Duchochois

Chloride of nickel and potassium ferrocyanate produce a fine brown.

Photographic Reproduction Processes Peter C. Duchochois

Prussian blues are transformed, the former into ferroso-ferric hydrate, with formation of ferrocyanate, and the latter into ferric hydrate.

Photographic Reproduction Processes Peter C. Duchochois

All this being ready, the margin of the proof is turned upwards — so as to form a disk of which the outside is the impressed surface — in order that the ferrocyanate solution does not find its way on the back of the proof, which would produce stains.

Photographic Reproduction Processes Peter C. Duchochois

This metal now converts the ferricyanate in the ferro compound, which, by another action, forms both cupric and uranic ferrocyanate.

Photographic Reproduction Processes Peter C. Duchochois

To make this evident, all that is necessary is _simply to leave out the ferrocyanate_ in the preparation of the paper, which thus becomes reduced to a simple washing over with the ammonio-citric solution.

Photographic Reproduction Processes Peter C. Duchochois

The purple red color of the copper salt which now forms the picture may be modified or changed in many ways, (38) viz., by soaking the picture, after the ferrocyanate of potassium has been washed out of the lights, in a solution of sulphate of iron.

Photographic Reproduction Processes Peter C. Duchochois

With gallic acid and the ferrocyanate of potash it forms two of the most sensitive photographic solutions with which we are acquainted.

History and Practice of the Art of Photography Henry Hunt Snelling 1856

The ferrocyanate of potash may be considered as containing three equivalents of hydrocyanic acid, two of potash and one of iron; but, unfortunately, we can only obtain half the acid from the salt, owing to the formation of a compound during its decomposition which resists the action of the acid.

American Hand Book of the Daguerreotype 1853

By boiling, however, the ignited residue with spirits of wine this difficulty is said to be overcome, as the ferrocyanate is absolutely insoluble in that menstruum, while the cyanuret, at that heat, freely dissolves, and is as easily re-deposited on cooling.

American Hand Book of the Daguerreotype 1853