The American annual of photography . trial, though this doesnot usually exceed 10 grams per liter for economical in the proportion of elon beyond this usually gives fog,though in the case of hydroquinone an increase in the propor-tion may prevent fog. The following formula will give ex-treme contrast on a positive emulsion without fog when usedfor reel development, whereas a reduction of the proportion ofhydroquinone to, say, 5 grams would give fog before any greatcontrast was obtained. Hydroquinone 25 g. Sodium Sulphite (desiccated) 33 g. Sodium Bisulphite g. Sodium Carbo
The American annual of photography . trial, though this doesnot usually exceed 10 grams per liter for economical in the proportion of elon beyond this usually gives fog,though in the case of hydroquinone an increase in the propor-tion may prevent fog. The following formula will give ex-treme contrast on a positive emulsion without fog when usedfor reel development, whereas a reduction of the proportion ofhydroquinone to, say, 5 grams would give fog before any greatcontrast was obtained. Hydroquinone 25 g. Sodium Sulphite (desiccated) 33 g. Sodium Bisulphite g. Sodium Carbonate (desiccated) 66 g. Potassium Bromide i-5 §• Water to 1000 cc. (B) The accelerator, in the form of carbonates or hydrox-ides of lithium, sodium, potassium or ammonium, is added toaccelerate the developing action of the developing agent. Iftoo much is added, the developer passes from a true developerto a fogging agent, that is, its reducing power is so great thatthe unexposed portions of the emulsion are reduced to metallic 24. A WOODLAND PHILOSOPHER. Rudolf Eickemeyer. silver also. The correct proportion of accelerator to be addedin any case can only be found by trial. Amidol does not re-quire the addition of an alkali, while in the case of hydro-quinone, if sufficient sulphite is present, the proportion ofsodium carbonate in many cases may be increased from 25 to100 grams per liter, without increasing the amount of fogproduced. C. Sulphite, in the form of sodium sulphite, bisulphite, orpotassium metabisulphite, is added to prevent oxidation of thedeveloper by the oxygen present in the air, which would other-wise cause oxidation fog. The proportion necessary to pre-vent undue oxidation is usually equivalent to 50 grams ofsodium sulphite per liter, though if sulphite is added in consid-erable excess of this sulphite fog is produced. The nature of sulphite fog has been carefully investigated byMees and Piper (Phot. Journal, 1911, p. 226, 1912, p. 221)who found that silver
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