Part 340

Pure water 2 ounces Solution No. I 1 ounce Solution No. II 1 ounce

«Metol-Bicarbonate Developer.»—Thoroughly dissolve

Metol 1 ounce In water 60 ounces

Then add

Sulphite of soda, crystals 6 ounces Bicarbonate of soda 3 ounces

To prepare with hydrometer, mix

Sulphite of soda solution, testing 75 30 ounces Bicarbonate of soda solution, testing 50 30 ounces Metol 1 ounce

Dissolved in 12 ounces water.

«Ferrous-Oxalate Developer.»—For transparencies and opals.

I.—Oxalate of potash 8 ounces Water 30 ounces Citric acid 60 grains Citrate of ammonia solution 2 ounces

II.—Sulphate of iron 4 ounces Water 32 ounces Sulphuric acid 16 drops

III.—Citrate of ammonia solution saturated.

Dissolve 1 ounce citric acid in 5 ounces distilled water, add liquor ammonia until a slip of litmus paper just loses the red color, then add water to make the whole measure 8 ounces.

Add 1 ounce of II to 2 of I, and 1⁠/⁠2 ounce of water, and 3 to 6 drops of 10 per cent solution bromide potassium.

To develop, first rinse developing dish with water, lay film or plate down, and flow with sufficient developer to well cover. Careful attention must be given to its action, and when detail is just showing in the face, or half-tone lights in a view, pour off developer, and well wash the film before placing in the fixing bath.

«Tolidol Developer.»—Standard formula for dry plates and films:

Water 16 ounces Tolidol 24 grains Sodium sulphite 72 (144) grains Sodium carbonate 96 (240) grains

The figures in parenthesis are for crystals. It will be seen that in every case {526} the weight of sulphite required in crystals is double that of dry sulphite, while the weight of carbonate crystals is 2 1⁠/⁠2 times as much as dry carbonate.

For tank development Dr. John M. Nicol recommends the standard formula diluted with 6 times the amount of water, and the addition of 1 drop of retarder to every ounce after dilution.

To obtain very strong negatives:

Water 16 ounces Tolidol 50 to 65 grains Sodium sulphite 80 (160) grains Sodium carbonate 120 (300) grains

On some brands of plates the addition of a little retarder will be necessary.

If stock solutions are preferred, they may be made as follows:

Solution A

Water 32 ounces Tolidol 1 ounce Sodium sulphite 1 (2) ounce

Solution B

Water 32 ounces Sodium sulphite 2 (4) ounces

Solution C