The “Drunkometer”


First “drunkometer”: Dec. 31, 1938

Thanks to the end of Prohibition and a boom in car sales, drunk driving had become a fast-growing problem in America in the 1930s. But on this New Year’s Eve, police in Indianapolis, Indiana went out armed with a new weapon to fight against people who had gotten behind the wheel after having too much to drink.

It’s a contraption called a “drunkometer”  and it’s the invention of an Indiana University chemist named Rolla Harger. He had been working on the device since the early 1930s and had patented it two years earlier. The concept behind the drunkometer was pretty basic. Drivers suspected of being drunk were asked to breathe into a rubber balloon, which was attached to a tube of purple liquid—a  weak solution of potassium permanganate in sulphuric acid.

If there was alcohol on their breath, the chemical solution changed color–the darker it got, the more alcohol they had in their system.  From the shade of the liquid, the cops could use a simple equation to estimate the alcohol level in a person’s bloodstream.  Previously, the only way police could check a driver’s alcohol level was to get a blood or urine sample; Neither was a very practical option on the roadside.  While the drunkometer looked a bit like a mini chemistry set, it was portable, able to fit into a small suitcase.

Harger made the device as simple as possible so that judges and juries would understand how it worked and police officers could easily be trained to use it. He also made the drunkometer hard to beat. Experiments showed that no illness affected the result, and that nothing a person might eat – garlic, cloves, strong onions – would make any difference. Once  police started using it, the drunkometer was found to have another advantage. A dramatic change in the color of the liquid could often make people admit how much they had drunk.

Sometimes Harger would ride along with the police to see how his invention was being used.  What he discovered was that a lot more people were driving drunk than he ever imagined.

The drunkometer was used by police departments all over the country until the 1950s when it was replaced by the breathalyzer, invented by another Indiana University professor, Robert Borkenstein. The breathalyzer is a much smaller and more sophisticated device that uses infrared spectroscopy to measure blood alcohol levels.



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