Franklin, and the smell of fart and urine

Benjamin FranklinIn addition to having become part of the popular imaginary as the man who raised a kite in the middle of a storm, he was also a rather ironic guy. To the point that he wrote a letter "To the Royal Academy of Farts" in order to propose to scientists that they will find some way to stop being awkward throwing in public:

Discover some healthy and unpleasant substance, to mix with our common foods, or sauces, that makes the natural discharges of windiness of our body not only harmless, but pleasant.

Franklin would be glad to discover today the smells of farts can be measured, as I explained in Measuring the smell of flatulence.

In that same letter, Franklin showed identical concern about the smell of urine:

Eating a few asparagus will give our urine an unpleasant smell; and a turpentine pill no larger than a pea, will confer the pleasant aroma of violets.

The truth is asparagus consumption does influence the smell of urine, although not in all cases (approximately it happens in half of the population, for genetic reasons). This is due to the breakdown in the body of a chemical substance present in asparagus (which is believed to be asparagine acid), which produces methyl mercaptan and other sulfur-containing compounds.