In the early 19th century, Bernard Courtois had a factory that produced saltpeter (potassium nitrate), which was a key ingredient in ammunition, and thus a hot commodity in Napoleon’s France. On top of that, Courtois had figured out how to fatten his profits and get his saltpeter potassium cheaply. He collected the seaweed that washed up daily on the shores, burned it, and extracted the potassium from the ashes.
One day, while his workers were cleaning the tanks used for extracting potassium, they accidentally used a stronger acid than usual and strange clouds billowed from the tank. He noticed dark crystals on all the surfaces that had come into contact with the fumes. He had them analyzed and discovered previously unknown element, which he named iodine, after the Greek word for “violet.”
Iodine is plentiful in saltwater and concentrated in seaweed. It was soon discovered that goiters, enlargements of the thyroid gland, were caused by a lack of iodine in the diet. Eventually, in addition to its other uses, iodine his routinely added to table salt. Of course you know that they also put in other ingredients to keep the salt from clumping like it used to. For you old timers, rice in the shaker is no longer needed. Check the container next time you buy salt to see if it is iodized.