Chromic Acid

Chromic Acid is the mixture of concentrated sulfuric acid and a dichromate ion, which may contain a variety of compounds. It is also known as Tetraoxochromic acid or Chromic(VI) acid. 

More About Chromic Acid

There are two forms of chromic acids:

  • Molecular Chromic Acid (H2CrO4): Similar to H2SO4.
  • Dichromic Acid (H2Cr2O7): A fully protonated form of the dichromate ion(Cr2O7).

Following are the properties of the chemical

Chemical FormulaH2CrO4 or H2Cr2O7 
Molecular Weight 118.008 g/mol
Density 1.201 g/cm3
Melting Point197℃
Boiling Point250℃

Chromic acid structure
Chromic acid structure (Source)

Chromic Acid Test for Alcohols and Aldehydes

Now, let’s have a look at this test for alcohols and aldehydes which involves this chemical (Oxidation Mechanism)


Three drops of the unknown compound to be tested are mixed with 5 drops of acetone and 5 drops of tetraoxochromic acid solution.


The formation of a bluish-green colour of the Cr(III) ion indicates a positive test. If the unknown compound is insoluble in water, two layers are present. A bluish-green colour in either layer indicates a positive test.


Aldehydes and primary alcohols are oxidized to carboxylic acids while the Cr+6 ion in the tetraoxochromic acid is reduced to Cr+3 ion.

Secondary alcohols are oxidized to ketones while the Cr+6 ion in the tetraoxochromic acid is reduced to Cr+3 ion.

Applications of Chromic Acid

  • Used in chromium plating.
  • Used in ceramic glazes and colored glass.
  • Can be used to clean laboratory glassware.
  • Used in hair dye.


What is the formula for chromic acid?

The formula is H2CrO4(molecular form) and H2Cr2O7(dichromic form).

What is chromic acid?

It is the mixture of a concentrated sulfuric acid and dichromate ion.

How is chromic acid prepared?

Sodium dichromate or potassium dichromate must be first combined with water to produce a paste. Continuous addition of concentrated sulfuric acid and mixing produces tetraoxochromic acid.

More on Inorganic Compounds

Copper Hydroxide (Cu(OH)2)Hydrosulfuric Acid (H2S)
Chlorine Trifluoride (ClF3)Barium Carbonate (BaCO3)
Sodium Sulfate (Na2SO4)Ammonium Persulfate ((NH4)2S2O8)

Leave a Comment

Scroll to Top
Scroll to Top