Pigments containing chromium

Perceived or Real Health and Safety Issues — There are a number of issues or perceived issues which customers encounter with the original MEK-based inks. The use of MEK has its share of concerns, based upon the smell and perception that it is a harmful material. Indeed, for this reason inks have been formulated with alternative solvents such as ethanol and methanol, as well as previously discussed acetone, and a variety of acetates, such as ethyl acetate. Some of these solvents have unpleasant odour, some more pleasant smell some have a lower toxicity level. That said, methanol is commonly used as a low odor replacement, but could probably be considered a more toxic ingredient Another component which is often replaced is the Solvent Black 29 dye, this dye does contain chromium as the counter ion and the toxicity concerns of having free Chromium 6 ions in an ink can be an issue for some applications or customers. Dyes with alternative counter ions or pigments have been chosen to replace this material. These requirements are often found in the food processing or pharmaceutical application areas, although they can occur with any customer. 

Estimation of Chromium.—In the analysis of chromites or of other substances containing chromium, such as leather ashes, pigments, etc., it is first necessary to obtain a solution. This is done by finely powdering the substance and heating it with a suitable flux in a crucible, preferably of nickel. Many fluxes have been employed, usually caustic alkali or alkali carbonates, but the one in most common use at present is sodium peroxide, whereby the chromium compound is rapidly converted to a chromate. - Excess of alkali is removed by boiling with ammonium carbonate, which also precipitates any iron present. The filtrate is then acidified with dilute sulphuric acid and the chromium estimated either by gravimetric or volumetric methods. 

Paints often contain solvents such as toluene, xylene, halogenated aromatic hydrocarbons, and methylene chloride, as well as heavy metals in their pigments including chromium yellow, lemon yellow (barium chromate), vermilion red (cadmium and mercuric sulfides), and flake white (lead). Both acute and chronic exposures to toluene and xylene are associated with neurotoxicity and can also damage the liver and kidneys. 

Solvent washes and sludges, caustic washes and sludges, or water washes and sludges from cleaning tubs and equipment used in the formulation of ink from pigments, driers, soaps, and stabilizers containing chromium and lead. 

A few dyes and pigments are considered to be carcinogenic, by US regulatory agencies. Benzidine dyes have already been mentioned. Lead chromate pigments contain both lead and hexavalent chromium, and as such are defined by EPA as carcinogenic. Experimentally,... 

Siberian red lead. Chrome red is Pb CrOj, lead oxide chromate. In our day the use of color pigments containing lead and hexavalent chromium is of course restricted for environmental reasons. 

The pigment chrome oxide green contains chromium(lll) oxide. Write the correct formula for chromium (111) oxide. 

The pigment chrome oxide green contains chromium(lll) oxide. 

Basic lead silicochromate is composed of basic lead chromate and basic lead silicate firmly bound to a silica core. It was used in coatings for metal protection in structural steel, and finer grades were used in electrocoat paints. Because these pigments contain both lead and hexavalent chromium, due to toxicity and human health reasons, they have lost their commercial importance. 

Salter (1869) states that this is an artificial ultramarine (q.v.) holding a middle position between French blue and permanent blue , adding that it may be said to hover in tint between a rich ultramarine and cobalt [blue] . It was stiU a current term for synthetic ultramarine when Heaton was compiling a hst of pigment synonyms in 1928, though Mayer (1991) on the other hand states that the name originally apphed to a variety of cobalt blue which contains chromium, a shade now termed cerulean blue chromium (perhaps chromimn cobalt aluminium oxide, qq.vl). Finally, it was also apparently synonymous with Prussian blue (q.v). 

Many plastics converters prefer to utilize colorants other than those that present potential health hazards. Colorants of these types are commonly restricted by legislation that limits their use. Many of the most weatherfast and heat stable inorganic pigments contain significant levels of heavy metals, specifically hexavalent chromium, lead, mercury, and cadmium, so... 

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