The Living Age 1374, 1.10.1870
The mode of manufacturing the substance for the beautiful pigment obtained by the ancients from the lapis lazuli, or azure stone, was, says the Scientific Review, like many other great inventions, the result of accident. A German chemist, whilst experimenting with anhydrous discovery that an exquisite blue colour was produced. He came to the conclusion that the blue colour of the ultramarine was probably due to sulphur and sulphuric acid, and at once instituted some experiments with alumina, soda, sulphur, and sulphuric acid, and succeeded, after repeated failures, in actually imitating the precious stone. The artificial material is said to be successfully formed by evaporating 100 lbs. of solution of sulphide of sodium mixed with 25 lbs. of dry china clay and 1-2 lb. of crystals of copperas; the dry mass is then heated in a muffle to a red heat, washed, and again heated.