chromate


Also found in: Dictionary, Thesaurus, Medical, Wikipedia.
Related to chromate: lead chromate, Barium chromate, strontium chromate

chromate

any salt or ester of chromic acid. Simple chromate salts contain the divalent ion, CrO42--, and are orange

Chromate

 

any one of a group of salts of chromic acid and isopolychromic acids. The salts of chromic acid, H2CrO4, namely monochromates or simply chromates, are discussed below.

Chromates are stable only in an alkaline medium; upon acidification, they are converted to dichromates. Potassium chromate and sodium chromate are the most important chromates.

Potassium chromate, K2CrO4, is a yellow crystalline substance, with a density of 2.732 g/cm3 and a melting point of 968.3°C. It is readily soluble in water: 62.9 g at 20°C and 79.2 g at 100°C in 100 g of water. It is produced by the action of potassium hydroxide, KOH, on potassium dichromate, K2Cr2O7.

Sodium chromate, Na2CrO4, is also a yellow crystalline substance, with a density of 2.72 g/cm3 and a melting point of 790°C. A hygroscopic compound, it is soluble in water: 80.2 g in 100 g of water at 19.5°C. It is produced by roasting the natural chromite FeCr2O4 with dolomite and sodium carbonate at 1150°–1200°C, then leaching out Na2CrO4 from the sintered mass formed, and finally subjecting the solution to evaporation and crystallization.

Sodium chromate and potassium chromate are used as chemical reagents, as mordants for dyeing textiles, and as components of tanning solutions in the leather industry. They are also used for seed treatment and as wood preservatives.

REFERENCE

Pozin. M. E. Tekhnologiia mineral’nykh solei, 4th ed., parts 1–2. Leningrad, 1974.

A. B. SUCHKOV

chromate

[′krō‚māt]
(inorganic chemistry)
CrO42-
An ion derived from the unstable acid H2CrO4.
A salt or ester of chromic acid.
(mineralogy)
A mineral characterized by the cation CrO42-.

chromate

To coat a metal surface with a rust-inhibiting primer of lead or zinc chromate.
References in periodicals archive ?
As they age, the small lead chromate particles are completely reduced to chromium oxide, while larger ones maintain a core of lead chromate that is coated in a shell of chromium oxide.
METHODS: BALB/c mice were repetitively treated with particulate basic zinc chromate or saline using an intranasal exposure regimen.
Chromate chemicals have previously been successfully treated in situ in neutral Ph conditions, but this study is unique in that it concentrates on extremely alkaline conditions, which are potentially much more difficult to treat.
Key words Chromate--chromium--chromosome instability--epigenetic changes--genomic instability--hexavalent chromium--lead chromate--mutations--zinc chromate
According to local residents the chromate was extracted by local for many years and was exported to Pakistan and then sent to China.
Workers in the 5th Maintenance Squadron identified several areas that were endangering their workers: Strontium Chromate levels that were 80 times above AFOSH standards; airborne particles that were 50 percent above occupational exposure limits; no sprinkler heads in exhausting ducts which could encourage fire proliferation throughout A/C dock; and inability to check airflow to know when dangerous conditions existed.
Available in heights from 12U to 44U and widths of 19", 23" and 24", FCC shielded S-Series Cabinets I have BeCu gasketing applied to all seams and joints to ensure paint-free electrical contact areas with optional clear chromate.
Powder coating technologies can reduce or eliminate risk and cost associated with the use of hazardous solvent-borne organic chromate coatings.
Color pigments include high-value Synergy pigments designed to reduce costs for formulators of industrial coatings; Meteor and Meteor Plus complex inorganic pigments for applications requiring heat resistance and exterior durability; Engeltone organic pigments in a wide spectrum of colors; Engeltone low-soluble cadmium pigments for uses requiring good heat and light stability; and Engeltone lead chromate and moly orange pigments for cost-effective coloring.
When chromate ions inside the mineral absorb electrons, the mineral turns green or brownish.
Obtained results are believed to serve better understanding of corrosion protection mechanism of aluminum alloys by conducting polymers and possess practical significance for finding alternatives to chromate conversion coating technology.