174. MOSAIC GOLD
Mosaic gold, or aurum mosaicum, is used for inferior articles. It is prepared in the following manner: 1 lb. of tin is melted in a crucible, and 1/2 lb. of purified quicksilver added to it; when this mixture is cold, it is reduced to powder, and ground with 1/2 lb. of sal-ammoniac, and 7 ozs. of flower of sulphur, till the whole is thoroughly mixed; they are then calcined in a mattrass, and the sublimation of the other ingredients leaves the tin converted into the aurum mosaicum, which is found at the bottom of the glass, like a mass of bright flakey gold powder. Should any black or discoloured particles appear, they must be removed. The sal-ammoniac used here must be very white and clear, and the mercury quite pure and unadulterated. When a shade of deeper red is required, it can easily be obtained by grinding a very small quantity of red lead along with the above materials.