Note 22 — Chapter XX · SULPHUR, SELENIUM, AND TELLURIUM
George Kamensky translation
During recent years (beginning with Schulze, 1882) it has been found that many metallic sulphides which were considered totally insoluble do, under certain circumstances, form very unstable solutions in water, as already mentioned in Chapter I., Note 5757. Arsenic sulphide is very easily obtained in the form of a solution (hydrosol). Solutions of copper and cadmium sulphides may also be easily obtained by precipitating their salts CuX2, or CdX2, with ammonium sulphide, and washing the precipitate; but they are re-precipitated by the addition of foreign salts.