ULTRAMARINE (from Lat. ultra, beyond marinas, marine, from mare, sea). A blue pigment originally' obtained from the mineral lazulitc, or lapis lazuli (q.v.). The finest specimens of lazulite conic from various locali ties in Persia, Siberia, and Chile, and when ground form the pigment; but. as only a very small proportion of that mineral is available, the pigment is very expensive. In 1S28 Guimet, of Toulouse, was successful in producing it on a commercial scale, and almost simultaneously a synthetical method for its preparation was an nounced by Gmelin, of Tilbingen. For the manu facture of artificial ultramarine, sodium sul phate, china clay, and carbon are ground to gether and heated in crucibles at a red heat for from six to nine hours. The resulting raw ultra marine, which is of a somewhat dull green color, is then crushed, mixed with powdered sulphur; and placed upon a roasting furnace, where it is heated with excess of air until the sulphur has been entirely burned off, when the mass assumes a bright blue color. A so-called direct method, which is said to yield better results, consists in using a mixture of sulphur 110 parts, china clay 100 parts. soda ash 90 parts, charcoal 20
parts, with some infusorial earth. These ma terials, after being carefully ground, well mixed, and pressed, are calcined in a nufille-furnace and yield, after heating from 12 to 18 hours, a blue ultramarine, which is then washed, ground, and dried. The pigment finds extensive use in the arts as a coloring material, owing to its bril liancy as a body color and high coloring power, especially in calico printing, in the manufacture of blue printing ink, for the printing of wall paper, in the making of blue writing paper, as a paint, and in the manufacture of blue mottled soap. It is also used as a whitening agent. cor recting the yellow tinge in writing and printing papers, in cotton and linen goods, sugar, etc. Cobalt ultramarine, or 'Thenard's blue,' is a pigment prepared by mixing freshly precipitated alumina with cobalt arsenate or phosphate, dry ing the mixture, and then slowly heating it to redness. Yellow ultramarine is a pigment con sisting of barium chromate.