Mercury-cadmium pigments

Cadmium pigments Mercury cadmium pigments Lead chromate yellows Lead molybdate oranges Iron blues Chrome greens Bismuth vanadate... 

Mercury-cadmium pigments were developed in the early 1950s as a more cost-effective alternative to cadmium sulfoselenides. Mercury replaces part of the cadmium in the cadmium sulfide compound and eliminates the need for selenium. The resulting pigments range from deep orange to a maroon and offer a cleaner, brighter chroma than their cadmium counterparts. Manufacture is the same as for cadmium sulfides, except that mercury salts are added to the cadmium solution that is reacted with the alkali sulfide solution to cause precipitation. 

Mercury-cadmium pigment performance is somewhat lower than cadmium pigment performance. They are inferior to sulfoselenides in lightfastness and are not recommended for exterior applications. Nor are they as heat stable as sulfoselenides. Maximum processing temperature is about 320°C. They are quite suitable for ABS but are not sufficiently heat stable for ploycarbonate or polyamide 6.6. 

Weatherability E = excellent, VG = very good, G = good, F = fair, P = poor, NR = not recommended. The ratings of the asterisked cadmiums are dependent on the imperviousness of the polymer to moisture vapor transmission. Cadmium yellows in tint and mercury-cadmium pigments are not recommended for exterior exposure. Ultramarine blue (double asterisk) performance is highly dependent on the degree of acid exposure. 

The colorants affected by this legislation include the lead chromate and lead molybdate yellows and oranges, cadmium pigments, and mercury cadmium pigments (which were little used by the time this legislation began to take effect). 

A third form of cadmium pigments includes the mercury cadmiums. Mercuric sulfide (HgS) forms soHd solutions up to about 20 mol % with the oranges, reds, and maroons. The heat stabiUty is improved up to 370°C, and the costs are somewhat lower than the CP grades. The mercury cadmiums are slightly more reactive, but have excellent bleed resistance. 

Figure 27. Crystal lattice of cadmium pigments (wurtzite structure) a) Sulfur (selenium) b) Cadmium (zinc, mercury)...

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). 

Mercury. - Cadmium. - Polycyclic Aromatic and Heteroaromatic Hydrocarbons. - Fluorocarbons. -Chlorinated Paraffins. - Chloroaromatic Compounds Containing Oxygen. - Organic Dyes and Pigments. - Inorganic Pigments. - Radioactive Substances. - Subject Index. 

As stated previously throughout this chapter, the pigment types most adversely impacted by this series of federal and state regulations are cadmium, mercury-cadmium, lead chromate, and lead molybdate colorants. Generally, these regulations make a distinction between hexavalent chromium, which is preceived as carcinogenic, and trivalent chromium. It is this distinction that allows the con-... 

In yellow CdS, which is the basis of the cadmium pigments, both the cadmium and the anion can, within certain limits, be replaced by ions with similar radii. The incorporation of zinc is industrially important in the manufacture of greenish yellow pigments, (Cd,Zn)S, as is that of mercury in (Hg,Cd)S and selenium in Cd(S,Se) for the production of a color range from orange to red to bordeaux red. 

The cadmium mercury sulfide pigments were developed in specific response to adverse economic conditions in the supply of selenium in the later 1940s, this type being patented in the US in 1948 (USP 2,878,134). According to Moore, the cadmium mercury sulfides are virtually identical in behaviour and appearance to the cadmium selenide sulfides, but of lower cost. 

The Colour Index (1971) lists two red cadmium pigments. Cl Pigment Red 108 and Cl Pigment Red 113. Compositionally these relate to cadmium sulfide selenides (CdSjcCdSe) and pure cadmium selenides (CdSe) as well as cadmium mercury sulfides (CdS.xHgS) q.v.). Co-precipitates with barium sulfate q.v.) are also known, sometimes referred to as cadmium red lithopone Colour Index, Cl 77202). 

The mercury sulfide compounds are undoubtedly the most important of the mercury group pigments as they include the red mineral cinnabar (HgS) and its synthetic analogue mercury(ll) sulfide, commonly known as vermilion q.v.). Two other crystal modifications of mercury(ll) sulfide occur, the hypercinnabar tyqie (P-HgS) and the metacinnabar type (a -HgS), the latter primarily significant as a black alteration product. Additionally, cadmium mercury sulfide ((Cd,Hg)S) is relevant in the context of cadmium sulfide pigments. 

Moore (1973) Moore, E.L. Cadmium/Mercury Sulfides Pigment Handbook 1 Patton, T.C. (eds.) lohn Wiley, New York (1973)395-399... 

Pigment color is determined by the ratio of Cd, and Zn or Hg if present, to S and Se in the product and can be changed all the way from primrose to maroon. Mercury substitution for cadmium yields (Cd, Hg)S pigments with ted and maroon shades similar to those obtained with selenium substitution. The Cadmium Association provides the simple diagram given in Figure 5 showing the color and composition correlation. 

The most common toxic metals in industrial use are cadmium, chromium, lead, silver, and mercury less commonly used are arsenic, selenium (both metalloids), and barium. Cadmium, a metal commonly used in alloys and myriads of other industrial uses, is fairly mobile in the environment and is responsible for many maladies including renal failure and a degenerative bone disease called "ITA ITA" disease. Chromium, most often found in plating wastes, is also environmentally mobile and is most toxic in the Cr valence state. Lead has been historically used as a component of an antiknock compound in gasoline and, along with chromium (as lead chromate), in paint and pigments. 

Electrolux is the world s largest producer of powered appliances for kitchen, cleaning and outdoors. They have created comprehensive Environmental Product Declarations (EPDs) for many of their product lines. Information within the product profiles details chemicals that have been banned as well as the percentage and types of materials and how they have improved material choices. Forexample, plastic components do not contain cadmium, lead, mercury or their compounds or chlorinated or brominated flame retardants metal components are not coated with cadmium, chromium, or nickel and metal paints do not contain pigments and additives based on heavy metals. Many Electrolux products are also PVC-free. 

Pigments and dyes provide paint and ink colors. Many highly toxic pigments, such as copper acetate (blue-green), arsenic trisulfide (yellow), and mercury II iodide (red), are no longer used. However, other hazardous pigment compounds, such as lead carbonate, mercury II sulfide, and cadmium sulfide, are still used today. These compounds present a danger to those artists who use their mouths to make a brush more pointed. 

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