The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Mercuric Chloride                                       Methylated Spirit
Mercuric Chloride (Ger., Quecksilberchlorid, Mercurichlorid, Sublimat; Fr.. Bichlorure de mercure; Ital., Bicloruro di mer-curid). HgCl2 = 27i. Synonyms: Perchloride of Mercury, Bi-chloride of Mercury, Corrosive Sublimate, Sublimate, Muriate of Quicksilver. Can be prepared by heating mercury in an excess of chlorine, but it is prepared commercially by sublimation from a mixture of mercuric sulphate and common salt. It is usually met with in commerce in extremely heavy colourless crystalline masses or as a white powder. Specific gravity : 5*43. Solubility : 1 in 19 of cold, 1 in 3 of hot water, 1 in 5 of rectified spirit, 1 in 6 of ether. It sublimes without decomposition, and melts at 5090 F. It is used for Intensification (q.v.). Its solution in water is liable to decomposition ; but any soluble chloride tends to prevent this, and nearly all chlorides increase its solubility in cold water, a compound salt being formed. It is a powerful poison, 3 grs. being a fatal dose. The antidote is albumen, or white of egg, with which its forms an insoluble compound, followed by emetics. As the salt is readily absorbed by the skin, it is advisable to exercise care. For a convenient method of preparing a solution of mercuric chloride, see Calomel.
Mercurous Chloride. See Calomel.
Mercury (Ger., Quecksilber; Fr., Mercure; Ital., Mercurio). Hg = 200. Synonym: Quicksilver. Occurs native, but is chiefly obtained by treating the ore cinnabar, which is an impure sul-phide, obtained from China, Spain, California, and America. Mercury, at ordinary temperatures, is a brilliant silvery white metallic liquid, becoming solid at -4ooF. Specific gravity: 13-5. It has now but little photographic interest, but was used in the old daguerreotype days to develop the image.
Metagelatiue. Gelatine so altered by heat or acids as to have lost its setting properties.
Metallic Spots. These sometimes occur on albumenised paper, and are due to impurities, usually metallic iron, in the substance of the paper itself.
Methylated Ether. Ether prepared from methylated spirit. (See Ether.)
Methylated Spirit. See Alcohol, Methylated.