# What is the chemical reaction that occurs in a breathalyzer?

2Cr_2O_7^(2-) + 3C_2H_5OH + 16H^+ → 4Cr^(3+) + 3CH_3COOH + 11H_2O
That is breath alcohol would be oxidized by the orange dichromate to give green $C {r}^{3 +} \left(a q\right)$. I can still remember TV commercials of policemen administering the breath test, and then informing the delinquent driver the deadly words $\text{the crystals were green, sir!}$, meaning that the driver was in big trouble.