Griess experiment is mostly used for qualitative experiment of urine nitrite. Its principle is that gram negative bacteria such as Escherichia coli can reduce nitrate in urine as nitrite. Nitrite diazotizes p-aminobenzenesulfonic acid in Griess reagent to p-diazobenzenesulfonic acid, and diazepine sulfonic acid is combined with α – naphthylamine to form n-α-naphthylaminobenzenesulfonic acid, which is red.

Griess Reagent is in dry powder form and is only used in scientific research and is not suitable for clinical diagnosis and other purposes.