Mixed metal oxides chromium compounds

Wet mixes are usually dried before calcination. Calcination is performed continuously in rotary or tunnel kilns, or batchwise in directly fired drum or box furnaces. The temperature at which the mixed metal oxide pigments are formed can be reduced by adding mineralizing agents [3.75]. In the case of chromium rutile pigments, addition of magnesium compounds [3.81] or lithium compounds [3.80] before calcination improves thermal stability in plastics. 

Planar M30 units occur in the basic carboxylates of such metals as iron, ruthenium, manganese, vanadium and chromium the chromium compound has been known since 1919. The metal atoms are also linked by pairs of carboxylate ligands (often acetates), and have terminal ligands (generally pyridine or water). Mixed metal units, e.g. Fe2CrO,124 and mixed oxidation states, e.g. Ci CifO,1 ... 

Chromium. Chromium is not an easily analyzed element because three distinct standards are listed by OSHA (Tables IV and V ). One standard exists for hexavalent chromium, chromic acid and chromates, another standard for soluble chromium compounds and chromous salts, and another standard for insoluble chromium compounds and chromium metal. The permissible amount of chromium in air decreases as the oxidation state increases. The analysis of chromium is further complicated by the multiplicity of NIOSH methods for chromium compounds. Hexavalent chromium shall be collected on PVC filters, although a criteria document for chromic acid (14) specifies mixed cellulose ester filters. The analytical method described in the hexavalent... 

LIQUID AMMONIA (7664-41-7, anhydrous, compressed gas or cryogenic liquid 1336-21-6, solution in water) Difficult to ignite, but can detonate in confined spaces in fire. Reacts violently with strong oxidizers, acids (nitric, hydrochloric, sulfuric, picric, hydro-bromic, hydrochlorous, etc.). Shock-, temperature-, and pressure-sensitive compounds are formed with antimony, chlorine, germanium compounds, halogens, heavy metals, hydrocarbons, mercury oxide, silver compounds (azides, chlorides, nitrates, oxides). Fire and/or explosions may be caused by contact with acetaldehyde, acrolein, aldehydes, alkylene oxides, amides, antimony, boron, boron halides, boron triiodide, bromine, bromine chloride, chloric acid, chlorine, chlorine monoxide, o-chloronitrobenzene, l-chloro-2,4-dinitrobenzene, chlorosilane, chloromelamine, chromium trioxide, chromylchloride, epichlorohydrin, fluorine, hexachloromelamine, hypochlorites (do not mix ammonia with liquid household... 

Corrosion of condensate lines is a serious problem. It is compounded where both oxygen and carbon dioxide are present because it causes considerable quantities of hematite (Fe203) to develop. Corrosion of other boiler plant components, such as FW heaters, adds more metals to the mix, and corrosion debris typically includes iron, copper, nickel, zinc, and chromium oxides. 

The first source of chromium was found in the mineral crocoite. Today it is obtained from the mineral chromite (FeCr O ), which is found in Cuba, Zimbabwe, South Africa, Turkey, Russia, and the Philippines. Chromite is an ordinary blackish substance that was ignored for many years. There are different grades and forms of chromium ores and compounds, based on the classification of use of the element. Most oxides of chromium are found mixed with other metals, such as iron, magnesium, or aluminum. 

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