Acid Short Stop Bath

A bath used between the developer and the fixing bath to stop action of developer on print. It also helps to avoid stain and uneven development.

Acid Sulphuric

H2SO4 - II. Oil of Vitriol. Strongly corrosive, dense, oily liquid. Most universally used of all the acids. Has a great affinity for water, and in combining with it produces heat; therefore, care must be exercised in mixing it with water. The acid must be poured by degrees into the water, never the water into the acid, or an explosion will likely result. Used to acidify pyro solutions, also as a clearing bath for bromide prints developed with ferrous oxalate.

Acid Sulphurous


Colorless, acid liquid; suffocating sulphur odor. Must not be confused with sulphuric acid. Used in some developing solutions.

Acid Tannic

C14H10O9. Tannin. Yellowish powder or crytalline-like, lusterless scales. Soluble in 5 parts water, 2 parts alcohol. Almost insoluble in ether. Used chiefly in photography for hardening gelatin prints and films, but even for this purpose it is not to be recommended, as it is liable to cause a print to turn yellow in a short time.

Acid Tartaric


Colorless, transparent crystals or white powder; strongly acid taste. Soluble in about I part water, 3 parts alcohol, 5 parts glycerin, and slightly soluble in ether. Used in preserving emulsions containing silver nitrate in various sensitized papers.

Effects of Acid Water

All water should be tested before use. In most instances, if acid, it should be neutralized. (See Reference.)


A chemical property of light. Causes chemicals to combine and decompose. White light is actinic. Violet, indigo and blue rays are the most actinic, therefore are called aclinic rays, while the red, orange and yellow rays are known as non-actinic rays of light.


An instrument used for measuring the actinic power of light, and especially valuable for measuring the necessary exposure for plates and papers.

Adapter for Lenses

A brass ring having screw threads which permit of lenses being fitted into other flanges than those for which they were intended.


C6H3C1 (OH)2 or C6H3Br (OH)2 - II, 435-438. A developing agent produced by substituting for an atom of hydrogen in hydroquinon one atom of chlorine or bromide. Adurol is far more soluble than hydroquinon, possesses better keeping qualities, tends to give less contrast to the developed negative, and does not cause stains as readily.

Aerial Perspective

(See Perspective, Aerial.)


Long, transparent strips resembling goose-quill pith; also quadrangular translucent cakes of about 10 Gm. each. Soluble in hot water, forming a viscid, tasteless, odorless jelly. A substance prepared from certain species of sea-weeds, which latter are obtainable in the Pacific and Indian Oceans and Japan Sea. Suggested as a substitute for gelatin in dry plate emulsions, but is not so satisfactory.