PHOSPHORESCENT MASS.
See also Luminous Bodies and Paints.
Mix 2 parts of dehydrated sodium carbonate, 0.5 parts of sodium chloride, and 0.2 parts of manganic sulphate with 100 parts of strontium carbonate and 30 parts of sulphur and heat 3 hours to a white heat with exclusion of air.
PHOSPHOR BRONZE: See Alloys, under Bronzes.
PHOSPHORUS SUBSTITUTE.
G. Graveri recommends persulfocyanic acid = H2(CN)2S3 as meeting all the requirements of phosphorus on matches. It resists shock and friction, it is readily friable, and will mix with other substances; moreover, it is non-poisonous and cheaper than phosphorus.
PHOTOGRAPHY
Developers And Developing Of Plates.
No light is perfectly safe or non-actinic, even that coming through a combined ruby and orange window or lamp. Therefore use great care in developing.
A light may be tested this way: Place a dry plate in the plate holder in total darkness, draw the slide sufficiently to expose one-half of the plate, and allow the light from the window or lamp, 12 to 18 inches distant, to fall on this exposed half for 3 or 4 minutes. Then develop the plate the usual length of time in total darkness. If the light is safe, there will be no darkening of the exposed part. If not safe, the remedy is obvious.