6 декабря, 2015 
Pokraskin Of this small group of pigments, ultramarine blue (C. I. Pigment Blue 29) is the best known and by far the most important, although violet and pink pigments are also produced. Ultramarine blue offers excellent fastness to light and heat at moderate cost. Although capable of providing brilliant reddish-blue colours in application, ultramarine blue suffers from poor tinctorial strength. As an example, the pigment has less than one-tenth of the colour intensity of copper phthalocyanine, the most important organic blue pigment. A further deficiency of the pigment is rather poor resistance towards acids. Ultramarine blue pigments have a complex sodium aluminosilicate zeolitic structure. In essence, the structure consists of an open three-dimensional framework of AlO4 and SiO4 tet — rahedra and within this framework there are numerous cavities in which are found small sulfur-containing anions together with sodium cations which maintain the overall electrical neutrality. It has been conclusively demonstrated that the radical anion S3~ is the species responsible for the blue colour (2max 600 nm) of ultramarine blue pigments. It is both interesting and somewhat surprising that products of such high durability result when species such as S3~, which are otherwise quite unstable, are trapped within the ultramarine lattice.
Formerly derived from the natural mineral lapis lazuli, ultramarine blue pigments have, for more than a century, been manufactured synthetically. The materials used in the manufacture of ultramarines are china clay (a hydrated aluminosilicate), sodium carbonate, silica, sulfur and a carbonaceous reducing material such as coal tar pitch. For the manufacture of the blue pigments, the blend of ingredients is heated to a temperature of 750-800 °C over a period of 50-100 h, and the reaction mixture is then allowed to cool in an oxidising atmosphere over several days.
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