Pigments cadmium yellow

Production. The raw material for the production of cadmium yellow pigments is high-purity cadmium metal (99.99 %), cadmium oxide, or cadmium carbonate. If the metal is used it is first dissolved in mineral acid. A zinc salt is then added to the solution the amount added depends on the desired shade. The zinc salt is followed by addition of sodium sulfide solution. An extremely finely divided cadmium sulfide or cadmium zinc sulfide precipitate is formed, which does not possess any pigment properties. This intermediate product can also be obtained by mixing the cadmium or cadmium-zinc salt solution with sodium carbonate solution. An alkaline cadmium carbonate or cadmium zinc carbonate precipitate is formed which reacts in suspension with added sodium sulfide solution. 

Production. Cadmium red pigments are produced in a similar way to the cadmium yellow pigments. The cadmium salt solution is prepared by dissolving the metal in mineral acid and then sodium sulfide is added. A certain amount of selenium powder is dissolved in the sodium sulfide solution to obtain the desired color shade. In an alternative procedure, the cadmium solution is mixed with sodium carbonate solution to precipitate cadmium carbonate which is reacted with the selenium-containing sodium sulfide solution. 

Cadmium yellow pigments (CdS) are manufactured by adding sodium sulfide to dissolved metallic cadmium or a cadmium salt solution to precipitate the fine particle raw colorant, which does not yet have pigment properties. Calcination at temperatures between 600 and 700°C induces particle growth to ca. 0.2 pm at which optimum tinting strength and hiding power are attained. 

Stability of Recycled HDPE Bottle Crates After 5 years Service in a Xenon Arc. Weatherometer. Crates contain a cadmium yellow pigment. 

While cadmium yellow pigment was at first very rare due to the scarcity of the metal, it became more available to artists in the 1830s after cadmium started to be produced commercially in Upper Silesia (now Poland). A reference to cadmium sulfide is made in George Field s Practical Journal of 1809, where a yellow cadmium water color sample is discussed. Cadmium yellow was also exhibited by today s well known Artist Supply company, Winsor and Newton, at the important Crystal Palace exhibition of 1851, in England. 

While cadmium yellow pigment was at first very rare due to the scarcity of the metal, it became more available to artists in the 1830s after cadmium started to be produced commercially in Upper Silesia (now Poland). A reference to cadmium... 

As a consequence of the low opacity of the pigment, it was commonly adulterated with chrome and cadmium yellow pigments qq.v. Church, 1901 Gentele, 1860). 

According to a Composition of Pigments list given in a Winsor Newton catalogue of 1896, this was a variety of Naples Yellow prepared from Chrome Yellow and White Lead (cf. Carlyle, 2001). Heaton (1928) hsts this as a then-current term for an imitation Naples yellow compounded of cadmium and white lead . Doemer (1935) describes brilliant yellow as a very light mixture of cadmium yellow and either Cremnitz or zinc white . Fiedler and Bayard (1986), in their modem review of cadmium yellow pigments, state that the composition was of cadmium yellow and lead white, adding that vermilion qq.v.) was also sometimes included in the formulation. 

In countries with hot, damp climates, a shift in the shade of the product results after a relatively short time, due to oxidative attack. Thus ultramarine pigments are less resistant to weathering, and sulfidic cadmium yellow pigments become blue. 

Fig. 1.5 IR spectrum, obtained in ATR mode, of a sample of yellow pigment from Jose Benlli-ure s palette (1937). (BM) IR bands ascribed to the drying oil used as a binding medium. Interestingly, and (CS) appearing at 1569cm is associated with carboxylate groups from cadmium soaps formed as a consequence of natural aging...

The use of zinc yields greenish yellow pigments due to the lower lattice constants mercury and selenium lead to expansion of the lattice. With an increasing content of selenium, or especially mercury, the shades of the pigments change to orange, red, and ultimately to deep red (bordeaux). The brilliant colors of cadmium pigments are primarily due to their almost ideal reflectance curves with a steep ascent (Fig. 28). 

Cadmium yellow consists of pure cadmium sulfide (golden yellow color) or mixed crystals of zinc and cadmium sulfide [8048-07-5], (Cd, Zn)S, in which up to one-third of the cadmium can be replaced by zinc. The density of this pigment is 4.5-4.8 g/cm3 and its refractive index is 2.4-2.5. The prevalent parcticle size is approx. 0.2 pm with cubic to spheroidal habits. Cadmium yellow is practically insoluble in water and alkali, and of low solubility in dilate mineral acid. It dissolves in concentrated mineral acid with generation of hydrogen sulfide. 

The crude precipitated cadmium yellow is washed and then calcined at approx. 600 °C, at which temperature the cubic crystal form changes to the hexagonal form. This process determines the particle size distribution, which is essential for the pigment properties. 

The cadmium red pigment intermediate is obtained as a precipitate which is filtered off, washed, and calcined at approx. 600 °C. As with cadmium yellow, calcination yields the red pigment and determines the particle size, particle size distribution, and color shade. Analogously to the cadmium yellow process, cadmium red can be produced by direct reaction of cadmium oxide or cadmium carbonate with sulfur and the required amount of selenium at approx. 600 °C. 

The cadmium pigments are lightfast but, like all sulfide pigments, are slowly oxidized to soluble sulfates by UV light, air, and water. This photooxidation is more pronounced with cadmium yellow than with cadmium red and can still be detected in the powder pigment which normally contains 0.1 % moisture. 

Cadmium fluoride has similar uses to the zinc halide. Cadmium oxide is used in ceramic glazes the sulfate, as a source of other cadmium compounds and in the radio valve industry the sulfide is important as a yellow pigment for artists, and is used in the paint, soap, glass, textile, paper, rubber and pyrotechnics industries. Cadmium sulfide in admixture with other compounds such as the selenide gives rise to other pigments of value. It is also used in phosphors and fluorescent screens and in scintillation counters. Semiconductors such as CdS... 

The principal red and yellow pigments are Lead chromate chrome yellow, orange and red), zinc chromate zinc or buttercup yellow), barium chromate lemon yellow or yellow ultramarine) various products based on jerric oxide, hydrated (yellow) or anhydrous (red), both natural yellow and red ochres) and artificial Mars yellow, English red, etc.) red oxide oj lead minium or red lead) mercuric sulphide cinnabar, vermilion) antimony oxysulphide antimony cinnabar) cadmium sulphide cadmium yellow) basic lead antimonate Naples yellow). 

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