Ultramarine

Collier's New Encyclopedia (1921)

a brilliant blue color, in very extensive use by painters, paper stainers, calico printers, and others. The substance previous to the year 1828 was obtained only from lazulite or lapis lazuli, a beautiful and costly mineral substance. The mineral being rare, and much prized for ornamental inlaying, and the color being of unapproachable brilliance and depth, it was an extremely expensive pigment. In consequence, strenuous efforts were made to obtain an equally valuable product by artificial means. In 1824 the French Société d'Encouragement pour l'Industrie Nationale offered a premium of 6,000 francs for the manufacture of an ultramarine blue, possessing all the qualities of that extracted from lapis lazuli, li, and in 1828 the prize was awarded to M. Guimet of Lyon, who after four years' investigation succeeded perfectly in producing the valuable substance by a synthetical process. The ultramarine thus made was declared by competent judges to be in every way equal to the natural product; t; and Horace Vernet, who was one of the first to use the material, after employing it in his famous picture, "The Battle of Fontenoy," declared the substance to be even superior to natural ultramarine. M. Guimet's factory has ultr continued since that time to manufacture ultramarine of the highest quality. His process was never made public; but in the same year, 1828, Gmelin, a German chemist, made public a process for manufacturing ultramarine, which was extensively taken up and worked in Germany. These two discoverers may thus be fairly credited with the joint honors of this most brilliant triumph of chemical research. The composition of artificial ultramarine varies considerably, as does also its color, the latter showing many tones of and violet, and there is fur ther a green ultramarine, which is obtained in an intermediate stage of the manufacture. It is prepared by first dissolving silica in caustic soda, to which hydrate of alumina is then added in the proportion of 30 of alumina to 35 of silica. The mixture is dried and mixed with an equal weight of sublimed sulphur and to this again is added a mixture of equal parts of sulphur and sodic carbonate, weighing as much as the silica and alumina mixture. The whole is then submitted for two hours to a red heat in closed crucibles, whereby green ultramarine is produced and this is again heated in crucibles till the desired blue hue is developed. Ultramarine is manufactured extensively in Germany, France, Belgium and the United States.