Jewelers' rouge is artificially made as follows: Pulverized saltpetre and common salt are mixed with pulverized green vitriol, the compound being stirred with water to a paste and boiled down to dryness in a crucible. This compound is heated in a Hessian crucible to a red heat until it becomes homogeneous and quiet. Then it is poured out, and, when cool, powdered, boiled with water, and washed. This powder should be slightly elutriated for the elimination of grains of sand which may have been imparted to it from the crucible. Collect the powder on a cloth and dry same. As a substitution for 50 parts of crystallized green vitriol, 25 parts of pure nitrate of soda, 18 parts of sodium sulphate and 13 parts of common salt may be employed. If more saltpetre is used the preparation has a reddish tinge, while an addition of the amount of potash sulphate gives it a more violet color. An addition of salt makes it browner and the jewelers' rouge is obtained in the lustrous lamina. A second method consists in the dissolution, in 4 parts of water, of 1 part of soda and the heating of this solution to the boiling point, gradually stirring into the boiling fluid a little more than 1/2 part of green vitriol, and continue the boiling. After the substance is cold, on the bottom of the vessel will be found a greenish-white mass of ferrous carbonate. The super-natant fluid is then poured off. the precipitation is washed in an abundance of water and then dried and converted into red ferric oxide by a little glowing in a crucible.