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Azure Blue, or Smalts

The common qualities are made by fusing zaffre (roasted cobalt ore calcined with siliceous sand) with 2681. Kirchoff's Method of Making Vermilion. This is said to yield vermilion is allowed to settle, and the clear liquid evapequal to the Chinese. Rub in a porcelain dish 100 parts mercury with 23 parts flowers sometimes added to the juice. of sulphur, moistening the mixture with a solotion of caustic potash. Next treat it with 53 parts hydrate of potash, mixed with an equal weight of water; warm it up and tritur- potash. A finer quality is obtained by preate it again. The water must be replaced as cipitating a solution of sulphate of cobalt, it evaporates, and the operation continued for by a solution of silicate of potash. Another 2 hours. The whole is now to be evaporated cobalt blue is obtained by adding a solution, to a thin paste, during constant trituration, of phosphate of soda to a solution of nitrate of and the heat removed the moment the color cobalt, and mixing the precipitate, washed, is of a good tint. Even a few seconds too but not dried, with 8 times its weight of fresh much or too little will injure the result. hydrated alumina. When dry, heat it to a When cold, the mass is washed with a solution cherry red. It is permanent, but has little of potash, and afterwards with pure water, and finally dried.