Calcium chromate

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Calcium chromate
Names
IUPAC name
Calcium chromate
Other names
C. I. Pigment Yellow 33
Calcium chromate (VI)
Calcium Chrome Yellow
Calcium dioxido-dioxo-chromium
Calcium monochromate
Gelbin
Yellow Ultramarine
Properties
CaCrO4
Molar mass 156.072 g/mol
Appearance Yellow solid
Odor Odorless
Density 3.12 g/cm3
Melting point 2,710 °C (4,910 °F; 2,980 K)
Boiling point Decomposes
anhydrous
4.5 g/100 ml (0 °C)
2.25 g/100 ml (20 °C)
dihydrate
16.3 g/100ml (20 °C)
18.2 g/100ml (40 °C)
Solubility Reacts with strong acids
Practically insoluble in alcohol
Vapor pressure ~0 mmHg
Hazards
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
327 mg/kg (rat, oral)
Related compounds
Related compounds
Potassium chromate
Sodium chromate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Calcium chromate is a bright yellow chemical compound, with the formula CaCrO4, often encountered as dihydrate.

Properties

Chemical

Calcium chromate reacts with sulfuric acid to release chromic acid or chromium trioxide, precipitating calcium sulfate.

Physical

Calcium chromate is a yellow solid, odorless, somewhat soluble in water.

Availability

Calcium chromate is sold by chemical suppliers, though in some countries, like EU states, its sale is restricted, as it is a hexavalent compound, which are classified as toxic and carcinogenic.

It can be found in nature in anhydrous form as the rare mineral chromatite, first identified in the arid areas on Israel.

Preparation

Can be prepared by adding calcium chloride to sodium or potassium chromate.

Projects

  • Make chromium trioxide

Handling

Safety

Calcium chromate, like all hexavalent chromium compounds, is highly toxic and carcinogenic on ingestion or inhalation. Handling it without gloves can cause dermatitis, and can also be absorbed through the skin in small amounts, usually if wet. Aqueous solutions are notorious for staining most materials.

Always wear gloves and goggles when handling it, and a dust mask or respirator when handling it as a powder to avoid inhalation of it, which could be fatal.

Storage

Calcium chromate should be kept in closed bottles, with a proper label and a hazard symbol.

Disposal

Calcium chromate can be safely reduced to the less harmful Cr(III) oxide with a reducing agent, such as ascorbic acid, or potassium/sodium sulfites/metabisulfites/tiosulfates.

References

Relevant Sciencemadness threads