The Dictionary Of Photography

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

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Alkali
Alpha Paper
Alkali. The antithesis' of an acid. Alkalies turn litmus paper blue which has been reddened by an acid. They pre-cipitate certain metals from acid solutions, as oxides or hydrates. Their chief characteristic, however, is their readiness to react with acids to form salts. The mineral alkalies are the hydrates of potassium and sodium, KHO and NaHO, also the hydrates of certain rarer metals, notably lithium. Ammonia NH3, hydrazine N2H4 and some other organic substances, are powerful alkalies. Alcalinity as a quality is not confined to bodies strictly called alkalies, as such salts as borax and the alkaline carbonates show alkaline properties to test paper. (See Acid, Acidity, and Alcalinity.)
Alkaline Development. See Development.
Allyl Sulphocarbamide; Allyl Thiocarbamide. See
Thiosinamine.
Alpha Paper. One of the first introduced of the commercial papers coated with a.chlorobromide emulsion, as suggested by Eder in 1883. Such papers are intended for development, and not printing out; and from the ease with which warm or cold tones can be obtained at will, and from its being possible to obtain prints by its aid at night which are equal to ordinary printed-out papers, it has received a good deal of attention. Several formulae have been given for this emulsion-paper. Wellington suggests the following : -
Heat both solutions to 66o C, and add A to B, shaking violently; then add 20 parts gelatine previously swollen in water and melted; shake the whole well, and pour out into a dish to
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