Preparations Of Gold

PREPARATIONS OF GOLD.--Chloride of Gold, freed from an excess of acid is slowly changed under the action of light; a regularly increasing darkness taking place until it becomes purple, the first action of the light being to whiten the paper, which, if removed from the light at this stage, will gradually darken and eventually develope the picture. This process may be quickened by placing the paper in cold water.

Chloride of gold with nitrate of silver gives a precipitate of a yellow brown color. Paper impregnated with the acetate of lead, when washed with perfectly neutral chloride of gold, acquires a brownish-yellow hue. The first impression of light seems rather to whiten than darken the paper, by discharging the original color, and substituting for it a pale greyish tint, which by slow degrees increases to a dark slate color; but if arrested, while yet, not more than a moderate ash grey, and held in a current of steam, the color of the parts acted upon by light-- and of that only--darkens immediately to a deep purple.