Cement chromium

Zinc phosphate, Zn2(P0 2> forms the basis of a group of dental cements. Chromium and zinc phosphates are utilized in some metal-treating appHcations to provide corrosion protection and improved paint adhesion. Cobalt(II) phosphate octahydrate [10294-50-5] Co2(P0 2 8H20, is a lavender-colored substance used as a pigment in certain paints and ceramics. Copper phosphates exhibit bioactivity and are used as insecticides and fungicides. Zinc, lead, and silver phosphates are utilized in the production of specialty glasses. The phosphate salts of heavy metals such as Pb, Cr, and Cu, are extremely water insoluble. 

Tannins occur in many plants and are separated by extraction. At present, only quebracho extract is used as a mud thinner in significant quantity in the United States. Quebracho is an acidic material and performs best at high pH. It is an excellent thinner for lime-treated and cement-contaminated muds. However, it is not effective at high salt concentrations. Sulfomethylated tannin products are functional over a wide range of pH and salinity and have either been treated with chromium for good thermal stabiUty (58) or are chrome free. Concentrations of tannin additives are ca 1.5—18 kg/m (0.5—6 lb/bbl). 

Over time a large variety of materials have been used, including ivory, stainless steel, chromium—cobalt, and ceramics for the acetabular component. None proved sufficient. The implant material composition must provide a smooth surface for joint articulation, withstand hip joint stresses from normal loads, and the substance must disperse stress evenly to the cement and surrounding bone. 

Vitahium FHS ahoy is a cobalt—chromium—molybdenum ahoy having a high modulus of elasticity. This ahoy is also a preferred material. When combiaed with a properly designed stem, the properties of this ahoy provide protection for the cement mantle by decreasing proximal cement stress. This ahoy also exhibits high yields and tensile strength, is corrosion resistant, and biocompatible. Composites used ia orthopedics include carbon—carbon, carbon—epoxy, hydroxyapatite, ceramics, etc. 

Iron carbide (3 1), Fe C mol wt 179.56 carbon 6.69 wt % density 7.64 g/cm mp 1650°C is obtained from high carbon iron melts as a dark gray air-sensitive powder by anodic isolation with hydrochloric acid. In the microstmcture of steels, cementite appears in the form of etch-resistant grain borders, needles, or lamellae. Fe C powder cannot be sintered with binder metals to produce cemented carbides because Fe C reacts with the binder phase. The hard components in alloy steels, such as chromium steels, are double carbides of the formulas (Cr,Fe)23Cg, (Fe,Cr)2C3, or (Fe,Cr)3C2, that derive from the binary chromium carbides, and can also contain tungsten or molybdenum. These double carbides are related to Tj-carbides, ternary compounds of the general formula M M C where M = iron metal M = refractory transition metal. 

Chromium and compounds SPA Chromic acid Sodium dichromate Anodizing Cement Dyes Electroplating Paint Tanneries... 

Acetylene works Acrylates works Aldehyde works Aluminum works Amines works Ammonia works Anhydride works Arsenic works Asbestos works Benzene works Beryllium works Bisulfate works Bromine works Cadmium works Carbon disulfide works Carbonyl works Caustic soda works Cement works Ceramic works Chemical fertilizer works Chlorine works Chromium works Copper works Di-isocyanate works Electricity works Fiber works Fluorine works Gas liquor works Gas and coke works Hydrochloric acid works Hydrofluoric acid works Hydrogen cyanide works Incineration works Iron works and steel works... 

Sulfoalkylated naphthol compounds are effective as dispersants in aqueous cement slurries. The compounds can also be applied in an admixture with water-soluble inorganic compounds of chromium to provide additives of increased overall effectiveness. Particularly suitable are sodium chromate or ammonium dichromate. a-Naphthol is reacted in an alkaline aqueous medium with formaldehyde to create condensation products. The aldehyde can be reacted with bisulfite to produce sulfoalkylated products [1404,1410]. 

Hazardous waste burning incinerators, cement kilns, and LWAKs do not follow a tiered approach to regulate the release of toxic metals into the atmosphere. The MACT rule finalized numerical emission standards for three categories of metals mercury, low-volatile metals (arsenic, beryllium, and chromium), and semivolatile metals (lead and cadmium). Units must meet emission standards for the amount of metals emitted. For example, a new cement kiln must meet an emission limit of 120pg/m3 of mercury, 54pg/m3 of low-volatile metals, and 180 pg/m3 of semivolatile metals. 

A.Macias. A. Kindness, F.P. Glasser, Impact of carbon Dioxide on the immobilization potential of cemented wastes Chromium,Cem.Concr.Res.27 (2), 215-225, 1997. 

A.K. Minocha, Pankaj Kumar, Jaswinder Singh, L.K. Aggarwal, C.L. Verma, Effect of molybdate (II), chromium (III) and (VI) metal ions on the setting time of ordinary Portland cement. Indian J. Env. Prot., 24, 771-774, 2004. 

Researchers for the German government have documented a variety of reasons why substitution fails to be carried out. For example, they detail how cement manufacturers in Scandinavia solved the problem of skin contact with cement containing hexavalent chromium back in the 1980s, but the information was not diffused to other European manufacturers. 

The conduct of the cement manufacturers in the case of chromium cements is one such case, as is the continuing resistance of mineral wool manufacturers to the introduction of the criteria biopersistence or biosolubility for a toxicological evaluation of mineral wools. One further example can be found in the case study examined in the course of the COIN project. In this example, the joint insistence of the three German manufacturers of titanium dioxide on the dumping of dilute acid in the North Sea in the early 1980s was ended by the unexpectedly speedy movement of one manufacturer . 

Repeated and prolonged skin contact with cement can result in dermatitis of the hands, forearms, and feet this is a primary irritant dermatitis and may be complicated in some instances by a secondary contact sensitivity to hexavalent chromium. In a study of 95 cement workers, 15 had a mild dermatitis of the hands, which consisted of xerosis with erythema and mild scaling of 20 workers who were patch tested with 0.25% potassium dichromate, one person had a mild reaction and the others were negative. 

Perone VB, Moffitt AE, Possick PA, et al The chromium, cobalt, and nickel contents of American cement and their relationship to cement dermatitis. Am Ind Hyg Assoc J 35 301-306, 1974... 

The major use (60%) for coloured inorganic pigments, such as iron oxides, is in the construction materials industry. Here they are used to colour roof and flooring tiles, fibrous cement and mortar. Many inorganic pigments are used in coloured baking enamels for metal appliances. Chromium oxide is used in the refractory industry, not for its colour but because of its ability to improve the properties of bricks used in furnace linings. 

According to the vendor, Cement-Lock technology has successfully removed polycyclic aromatic hydrocarbons (PAHs), PCBs, and tetrachlorodibenzo-1,4-dioxin (TCDD)/2,3,7,8-tetra-chlorodibenzofuran (TCDF) from soils and sediments in bench-scale tests. Metal concentrations were also reduced below detection limits in bench-scale tests. These metals included arsenic, cadmium, chromium, lead, nickel, mercury, and silver. 

Moulin, I. 1999. Lead, Copper, Zinc, Chromium(III) and (VI) Speciation in Cement Hydrated Phases. PhD thesis, Universite Aix-Marseille III, France. 

The application of lignosulfonate-chromium derivatives in oil well drilling mud has already been mentioned as a typical example of the above effects in combination with crosslinking. The use of lignosulfonates as active extenders in concretes is a further example of the applicability of the above effects (61). Another is the use of lignins as extenders for asphalt cement (70). 

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