On September 15, 1885 U.S. Patent No. 326,281 issued to Constantin Fahlberg on an improved composition of the artificial sweetener saccharine.

A few months earlier, on June 2, 1885, he received U.S. Patent No. 319,082 on saccharine itself:

Saccharine is still widely used today as an artificial sweetener (the sweetener in Sweet ‘n’ Low). Fahlberg allegedly noticed a sweet taste on his hands after work, and connected this with the compound benzoic sulfimide on which he had been working earlier that day. Oddly, two other other artificial sweeteners were discovered the same way — tasting the same way. Cyclamate was discovered in 1937 at the University of Illinois by graduate student Michael Sveda, who was working on an antipyretic drug. He noticed that his cigarette, which he had put down on the lab bench, had a sweet taste when he put it back in his mouth. Aspartame was discovered in 1965 by James M. Schlatter at the G.D. Searle company. He was working on an anti-ulcer drug and accidentally spilled some aspartame on his hand, and noticed it had a sweet taste when he licked his finger. A third artificial sweetener, Sucralose (the sweetener in Splenda) was discovered by accident in 1976 by Shashikant Phadnis at Queen Elizabeth College (now part of King’s College London), who was told to “test” a chlorinated sugar compound, but allegedly though he was asked to “taste” it, thereby discovering its exceptional sweetness.

We should all be grateful for their sloppy laboratory procedures, and they should be glad the didn’t accidently discover a new poison.