The Iodine Trade

Who would have thought that boring iodine would be in the news? But then a nuclear reactor throws out radioactive iodine-131 and suddenly everyone wants some. Why? Because saturating the thyroid with ordinary iodine prevents the take-up of radioactive iodine. Iodised salt is not much use for this as the iodine concentration is very low. It is only about four tablespoons of potassium iodate per tonne of salt and while this is is great against goitre it is useless against nuclear fallout.
Iodine was accidentally discovered in 1811 by Bernard Courtois, while trying to make gunpowder from seaweed. The antiseptic properties were used to save soldiers in the American civil war. Daguerre used it to make photographs. It was discovered by Chinese in 2700BC that seaweed could cure goitre, and in 1820 it was confirmed that iodine was the active ingredient. It used to be a way of life burning seaweed on the coasts of Ireland, Scotland and Brittany for the minerals needed by the alkali industry for fertilisers and the like. They would harvest the kelp, dry it and burn it, resulting in dense blocks of material ready to be shipped for processing. Gradually other sources were found that could be mined and the industry suffered. Iodine provided a valuable extra revenue that the kelp burners could earn but this was only temporary. When sodium iodate extracted as a by-product of saltpetre from Chile became available it threw thousands of crofters out of work and many were forced to emigrate. Nowadays iodine mainly comes from saltpetre and certain brine deposits.