Potassium chlorochromate

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Potassium chlorochromate
Potassium chlorochromate vial by woelen.jpg
Nice crystals of KCrO3Cl
Names
IUPAC name
Potassium chlorochromate
Other names
Peligot's salt
Potassium chlorochromate(VI)
Potassium monochlorochromate
Potassium trioxochlorochromate
Potassium trioxochromium chloride
Properties
KCrO3Cl
Molar mass 174.5472 g/mol
Appearance Light orange crystalline solid
Odor Odorless
Density 2.5228 g/cm3
Melting point 290–292 °C (554–558 °F; 563–565 K) (decomposes)
Boiling point Decomposes
Soluble
Solubility Very soluble in acetone
Vapor pressure ~0 mmHg
Hazards
Safety data sheet Fisher Scientific
Flash point Non-flammable
Related compounds
Related compounds
Potassium chromate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium chlorochromate is an inorganic compound with the formula KCrO3Cl.

It is sometimes called Péligot's salt, in recognition of its discoverer Eugène-Melchior Péligot.

Properties

Chemical

Addition of conc. hydrochloric acid to this compound will yield chromyl chloride.

When treated with 18-crown-6, it forms the lipophilic salt [K(18-crown-6]CrO3Cl.

Physical

Potassium chlorochromate is an odorless orange-ish solid, soluble in water and acetone, though it will slowly hydrolyze in the former if kept too long.

Availability

Potassium chlorochromate is sold by chemical suppliers.

Since it's a Cr(VI) compound, its sale may be restricted in the EU.

Preparation

Potassium chlorochromate was originally prepared by treating potassium dichromate with conc. hydrochloric acid:[1]

K2CrO4 + 2 HCl → 2 KCrO3Cl + H2O

Because of the equilibrium reaction, the yield of this reaction never can be 100%. High yield is favored by increasing the concentration of the hydrochloric acid and also by increasing the concentration of potassium dichromate in the solution, such that more chlorochromate(VI) can be crystallized from the solution. As the salt is susceptible to hydrolysis, the solution must not be boiled to dryness not should the wet crystals be dried at high temperatures.

A water-free route involves the reaction of chromyl chloride with potassium chromate:[2]

K2CrO4 + CrO2Cl2 → 2 KCrO3Cl

Projects

  • Oxidizer in organic chemistry

Handling

Safety

Potassium chlorochromate is very toxic upon ingestion (may cause acute poisoning and kidney damage amongst other complications) and it's also irritant to the human skin (may cause eye burns, irritation, allergy, or ulceration), or lungs if inhaled.

Storage

Potassium chlorochromate can be stored in glass bottles, away from reducing agents and humidity.

Disposal

A reducing agent, like sodium thiosulfate, sulfite or metabisulfite can be used to safely reduce hexavalent chromium compounds to Cr(III), which is far less harmful.

References

  1. https://woelen.homescience.net/science/chem/exps/KCrO3Cl/index.html
  2. https://onlinelibrary.wiley.com/doi/abs/10.1002/9780470132333.ch64

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