I

Saturated solution of ferricyanide of potassium ........... 1 part

Hyposulphite of sodium solution (1 in 10) 10 parts

II

Perchloride of iron .. 30 grains

Citric acid.......... 60 grains

Water.............. 1 pint

Belitski's Acid Ferric-Oxalate Reducer for Gelatin Plates

Water.............. 7 ounces

Potassium ferric oxalate............... 2.5 drachms

Crystallized neutral sulphite of sodium. 2 drachms

Powdered oxalic acid, from.........30 to 45 grains

Hyposulphite of soda. 1.5 ounces

The solution must be made in this order, filtered, and be kept in tightly closed bottles; and as under the influence of light the ferric salt is reduced to ferrous, the preparation must be kept in subdued light, in non-actinic glass bottles.

Orthochromatic Dry Plates—Erythrosine Bath (Mailman and Scolik)

Preliminary bath:

Water...... 200 cubic centimeters

Stronger ammonia. ... 2 cubic centimeters Soak a plate for 2 minutes.

Color bath: Erythrosine solution (1 in 1,000) . 25 cubic centimeters

Stronger ammonia (0.900)... 4 cubic centimeters

Water...... 175 cubic centimeters

The plate should not remain longer in the bath than 1.25 minutes.