Phosphorous Acid
in chemistry, H3PO3. Prepared by adding water to the when exposed to sunlight, changed from erally speaking, the rate of chemical aca creamy white to purplish brown. Genby John W. Draper, of New York Unition is proportional to the intensity of versity, who measured the rate of com the light, but the exact determination of bination brought about by light in a the activity of light was first suggested mixture of hydrogen and chlorine. the activity of light was first suggested the light, but the exact determination of photographic film, measuring the time required to darken the film to a standard tint. The action of light is not confined light is, for most practical purposes, into any particular wave length, but the active, and this fact is made use of in most active are the violet and ultraviolet, or so-called actinic, rays. Red PHOTOELECTROTYPE photographic dark rooms in which white light is excluded and red lamps or windows employed. The action of light produces on photographic plates and bromide papers an effect which is not immediately visible, but can be made so by further action of a chemical known as a developer.