![medieval manuscripts with ultramarine medieval manuscripts with ultramarine](https://parker.stanford.edu/uploads/spotlight/attachment/file/3340/4.jpg)
The negative charge on these ions is balanced by Na +
![medieval manuscripts with ultramarine medieval manuscripts with ultramarine](https://i.pinimg.com/736x/44/55/06/445506185125356b9464ca7cab72e18c--illuminated-letters-illuminated-manuscript.jpg)
X) groups that are the chromophore (color centre). Some of these cages contain polysulfide ( S n− Sodalite consists of interconnected aluminosilicate cages. Ultramarine is the aluminosilicate zeolite with a sodalite structure. Structure and classification of ultramarines Even a small addition of zinc oxide to the reddish varieties especially causes a considerable diminution in the intensity of the color. Hydrochloric acid immediately bleaches it with liberation of hydrogen sulfide. Its color is unaffected by light nor by contact with oil or lime as used in painting. Synthetic ultramarine is a more vivid blue than natural ultramarine, since the particles in synthetic ultramarine are smaller and more uniform than the particles in natural ultramarine and therefore diffuse light more evenly. The different ultramarines-green, blue, red and violet-are finely ground and washed with water. A blue product is obtained at once, but a red tinge often results. "Ultramarine rich in silica" is generally obtained by heating a mixture of pure clay, very fine white sand, sulfur and charcoal in a muffle furnace. The sulfur burns, and a fine blue pigment is obtained. The product is at first white, but soon turns green "green ultramarine" when it is mixed with sulfur and heated. "Ultramarine poor in silica" is obtained by fusing a mixture of soft clay, sodium sulfate, charcoal, sodium carbonate and sulfur. ( Flue-gas desulfurization is thus essential to its manufacture where SO 2 pollution is regulated.) The resultant solids are then ground and washed, as is the case in any other insoluble pigment's manufacturing process the chemical reaction produces large amounts of sulfur dioxide.The mixture is heated in a kiln, sometimes in brick-sized amounts.In the second step, air or sulfur dioxide at 350 to 450 ☌ is used to oxidise sulfide in the intermediate product to S 2 and S n chromophore molecules, resulting in the blue (or purple, pink or red) pigment.This yields a yellow-green product sometimes used as a pigment. The first part of the process takes place at 700 to 750 ☌ in a closed furnace, so that sulfur, carbon and organic substances give reducing conditions.The preparation is typically made in steps: powdered charcoal or relatively ash-free coal, or colophony in lumps.The raw materials used in the manufacture of synthetic ultramarine are the following: The blue color of the pigment is due to the S −ģ radical anion, which contains an unpaired electron. Some chloride is often present in the crystal lattice as well. The major component of lazurite is a complex sulfur-containing sodium-silicate (Na 8–10Al 6Si 6O 24S 2–4), which makes ultramarine the most complex of all mineral pigments. In the Colour Index International, the pigment of ultramarine is identified as P. It occurs in nature as a proximate component of lapis lazuli containing a blue cubic mineral called lazurite. The pigment consists primarily of a zeolite-based mineral containing small amounts of polysulfides. 5.3 19th century – the discovery of synthetic ultramarine.
![medieval manuscripts with ultramarine medieval manuscripts with ultramarine](https://i.pinimg.com/474x/76/83/94/7683949f50bceced754e91e27844fd6f--illuminated-manuscript-medieval-manuscript.jpg)