Potassium Dichromate is used for Chromyl chloride test.
When salt containing chloride is treated with Potassium dichromate (K2Cr2O7) and con. H2SO4 reddish brown vapours of chromyl chloride are obtained.
K2Cr2O7 + 4KCl + 6H2SO4 → 2CrO2Cl2 (Chromylchloride) + 6 KHSO4 + 3H2O
This reaction is used in the detection of chloride ions in qualitative analysis.
Other Uses are:
i) It is used in volumetric analysis
ii) In chrome tanning in leather industry
iii) In calico printing and dyeing
iv) In photography and in hardening gelatin film.