For all of our early-21st-century hand-wringing about how we all eat too much salt, sodium chloride is a vital chemical for human metabolism and we have evolved to crave it. It is claimed that salt is one of the founding pillars of civilization, because it enabled food to be preserved, it was one of the earliest goods to be manufactured, and it was one of the first articles to be traded.
Salt has been produced for centuries from one of three basic methods: by evaporation of sea water (because there are 36 quadrillion tons of salt dissolved in ocean waters), by digging it out of the ground, or by extraction of crystallized salt as brine (because there are 1 quadrillion tons of rock salt available in the earth’s crust). These days global annual production of salt (for eating, industry and melting ice on roadways) is currently over 200 million tons.
Here are some images from the Archives of Scientific American, showing a short glimpse of the history of this storied chemical compound. And as you peruse these images, perhaps consider that as long as there has been salt production, it has always been big business.