Solution of potassium dichromate is used as indicator for COD (Chemical oxygen demand) determination. Most commonly, a 0.25N solution of potassium dichromate i.e. K2Cr2O7 is used for COD determination, although for samples with COD below 50mg∕L, a lower concentration of potassium dichromate is preferred. K2Cr2O7 is used to reduce interfering substances such as organic and various oxydizable substances.