Stereoscopic Projection by Lantern Supplementary Lens
inches for near objects to several feet for distant objects. Mr. Chadwick's "Stereoscopic Manual,''mentioned in our Biblio-graphy (p. 76), is a convenient handbook, and is written by one who is an enthusiast in connection with the stereoscope. (See Anaglyph, Stereograph, Crystal Cubes, and Parallax Stereogram.)
Steroscopic Projection by Lantern. See Anaglyph.
Stripping Negatives. See Negatives, Stripping of ; also Reversed Negatives.
Suipho-Pyrogallol. A term given to a solution of pyro-gallic acid in conjunction with a sulphite, as first suggested by Berkeley. The original formula was : -
Pyrogallol ... ... ... ... ... I oz.
Sodium sulphite ... ... ... ... 4 ozs.
Citric acid ... ... ... ... ... oz.
Water ............... 9 ozs.
Sulphuric Acid (Ger., Schwefelsaure; Fr., Acide Sulfurique.) H,S04 = 98. It is prepared by roasting iron or copper pyritet and oxidising the sulphur dioxide. Specific gravity: 1*845. Is is used in photography as a clearing agent, and for many other purposes. It forms salts called sulphates. It is extremely corrosive and caustic. Great heat is evolved when it is mixed with water, the temperature being raised to nearly boiling point; great care, therefore, should be used in mixing it.
Sulphurous Acid (Ger., Schw efligwasserstoffsatire ; Fr., Acide Stilfureux). Sulphur dioxide is prepared by deoxidising sulphuric acid with charcoal; and this gas, when dissolved in water, forms a colourless liquid, with pungent sulphurous odour, and containing 5 per cent, of sulphurous anhydride, S02. Specific gravity, 1*025. 1* should be freshly prepared, as it changes by keeping into sulphuric acid. It is recommended for preserving pyrogallol, and forms one of the ingredients of Beach's Developer (q.v.). Care should be exercised in handling this, not to inhale the fumes, which are extremely irritating.
Supplementary Lens. See Amplifier and Lens; also Adon.