BARYTA PAPER.—A paper prepared with baryta, or barium chloride, and coloring matter. It has a fine, smooth surface, and is largely used in collotype printing. This paper is also employed in the aristotype process, as it offers a smooth surface for the gelatine or collodion emulsion, prevents it from sinking into the paper, and the coloring matter gives it a pleasing tint. It is manufactured chiefly in Germany, where it is known as Baryt-papier or Kreide-papier. A formula for its preparation is the following : I.
Gelatine, Heinrich's go grains Barium chloride .3o grains Distilled water. 5 ounces 2.
Ammonium sulphate 15 grains Distilled water 53 ounces Soak the gelatine in the water till soft, add the barium chloride, and dissolve by heat ; then add solution 2 in small quantities, shaking between each addition ; allow the emulsion to set ; break up into small pieces ; wash thoroughly, and add 7i grains of chrome alum previously dissolved in a little water.
BASE.—In chemistry, a metallic oxide capable of reacting with acids to form a salt. Metals, when they burn, produce bases, which, if soluble in water, have properties the reverse of acids. They are soft and slimy to the taste instead of sharp. They change red litmus paper to blue, or the opposite effect to acids, which change blue to red. If a base be brought together with an anhydride, the resulting compound which is generally formed is called a salt.
BASEBOARD.—The foundation of the camera, carrying the lens, front, bellows, and back portion. This should be as solid as possible, consistent with portability and compactness.
BASIC.—Pertaining to a base.
BASIC OXIDES.—Oxides which react with acids to form salts.