SCHWEINFURTH GREEN is a more beautiful and velvety pigment than the preceding, which was discovered in 1814, and remained for many years a profitable secret. M. Liebig having made its com position known, in 1822, it has been since prepared in a great many color-works. Braconnot published, about the same time, another process for manufacturing the same pigment. Its preparation is very simple ; but its formation is accom panied with some interesting circum stances. On mixing equal parts of ace tate of copper and arsenious acid, each in a boiling concentrated solution, a bulky olive-green precipitate is immedi ately produced ; while much acetic acid is set free. The powder thus obtained, appears to be a compound of arsenious acid and oxide of copper, in a peculiar state ; since when decomposed by sul phuric acid, no acetic odor is exhaled.
Its color is not changed by drying, by exposure to air, or by being heated in water. But, if it he boiled in the acidu lous liquor from which it was precipita ted, it soon changes its color, as well as its state of aggregation, and forms a new deposit in the form of a dense granular beautiful green powder. As fine a color is produced by ebullition during five or six minutes, as is obtained at the end of several hours by mixing the two boiling solutions, and allowing the whole to cool together. In the latter case, the precipitate, which is slight and flocky at first, becomes denser by de grees; it next betrays green spots, which progressively increase, till the mass grows altogether of a crystalline consti tution, and of a still more beautiful tint than if formed by ebullition.