Potassium chlorochromate

Potassium chlorochromate

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
Chemical formula	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
Solubility in water	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:

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:

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

Relevant Sciencemadness threads

• Synthesis of potassium chlorochromate(VI): KCrO3Cl