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Sabtr active Processes. Ill 381
cent solution of brilliant green, with 2 per cent sulfuric acid, or as quicker working a compound bath of :
Potassium ferricyanide 2 g.
Potassium iodide 3.5 g.
Ethyl green, 2 per cent sol 15 ccs.
Sulfuric acid, 10 per cent sol 1 ccs.
Water 1000 ccs.
The following basic dyes were suitable for this process : auramin, chrysoidin, vesuvin, fuchsin, methyl violet, safranin, rhodamin, thionin blue, methylen blue, malachite green and Victoria blue. These should be used in 0.05 per cent solution with an equal volume of ammonia. The following acid dyes could be used also, tartrazin, Victoria yellow, ponceau, brilliant orange, naphthalin blue, acid violet, acid fuchsin, eosin, erythrosin, rose Bengal in 0.1 per cent solution with half the weight of citric acid.
The author has found that the positives for this process should be of rather a soft character and absolutely free from fog, which causes a superficial veil of color. Fixation of the plates should be effected in a chrome alum fixing bath, and after washing immersion in a 25 per cent solution of formaldehyde for 15 minutes and drying without washing, gives the best results. The strength of the dye solutions should not exceed 0.25 per cent, and with the addition of 5 per cent of glacial acetic acid, which keeps the whites much purer, and facilitates after-washing. Frequent failures may be met with, and this is often traceable to want of acid in the iodizing and dyeing baths, therefore, if the baths are in repeated use a little acid should be added occasionally.
A. S. Cory62 suggested as an iodizing bath :
Potassium iodide 40 g.
Iodine 19 g.
Water 1000 ccs.
When the image is bleached, wash for 30 minutes and immerse in the dye bath, which should be from 1 : 2000 to 1 : 5000, for about 15 minutes, then wash in running water, or in 5 per cent solution of glacial acetic acid, then fix in 10 per cent hypo solution containing 5 per cent of tannin and the same weight of sodium acetate.
J. H. Christensen03 proposed some methods which are rather complicated, the main idea being apparently to use emulsions weak in silver salts. Very thin negatives were to be obtained by the use of diluted emulsions, such as would be quite useless for ordinary printing. The image was to be converted into a dye-absorbing compound, such as silver iodide, silver sulfocyanide or colorless cuprous iodide or sulfocyanide. A typical solution would be :
Potassium citrate 55.5 g.
Cupric sulfate 41.75 g.
Potassium thiocarbamid 20 g.
Acetic acid 25 ccs.
Water 1000 ccs.