A Few Grains of History
We humans have an interesting relationship with salt. This mineral, primarily consisting of Sodium (Na) and Chloride (Cl) atoms sharing a weak covalent bond, is often combined with other elements such as Calcium and Potassium. Salts are the resulting product of a neutralization reaction of a strong base and weak acid, like your traditional baking soda (sodium bicarbonate, base) and vinegar (acetic acid) volcanoes from elementary school. Though I wouldn't eat the result if I were you!
Humans require sodium as a nutrient, but we cannot manufacture it within our bodies, which means that in order to get it, we have to eat it. In the body, sodium regulates our water balance, helps manage our body's pH, and is active in the absorption of other nutrients in the small intestine.
The reason that salty foods like French fries and chips taste so good to us is, because we have evolved to seek out salty foods to stay alive. This is problematic now, because just about all of our prepared foods have salt added to them for seasoning and as a preservative. The key for humans to stay healthy now is to have the appropriate balance of salt.
Salt has also been important in the development of human civilization in a variety of ways (See the above clip from the History Channel). Most notably, as a key component to food preservation, salt helps to kill disease-causing bacteria in our food. It does so by drawing enough water from bacterial cells to stop cell reproduction.
There are a few different ways that salt can be produced for human consumption--mainly through evaporation from saline or seawater and by mining mineral deposits. Like any other commodity, nations close to the resource have an economic advantage. As a valuable spice, salt has been a traded commodity, a form of currency, and even caused war between nations.
Salt is currently receiving a bit of attention because of growing fresh water scarcity. According to the USGS, less than 3% of the Earth's water is fresh, the only water that can be used for hydration. A decreasing amount of fresh water is available due to a current recession in glacial waters and icecaps and over irrigation in agriculture, which reduces groundwater aquifers. Scientists are now turning toward advances in technology that allow us to yield fresh water from salt water.
Sounds easy enough, right? Just take out the salt. The process is actually fairly complex and takes a tremendous amount of energy.
Low-Tech Home Experiment
Here is a simple low-tech science experiment that will allow you to use passive solar energy to distill your own water (this video is brought to you by the St. Louis Science Center). Give it a shot. Readers and fans of the hit 2012 film adaptation of Yann Martel's Li of Pi will notice that this process was used by young Pi to get fresh water on the lifeboat.
Keeping with the theme of this week's earlier post on nonfiction, here is a great read that looks at the natural history of salt and the important role that it plays in the development of human civilization. Check it out from your library: available as hardcopy and as an eBook.