What is salt made of?

Chemists call ordinary table salt “sodium chloride” because it’s made of two chemical elements:  sodium and chlorine.  That’s amazing because pure sodium is a metal and pure chlorine is a yellow-green gas.  Sodium metal reacts explosively when dropped into water.  Chlorine gas is poisonous, used in gas warfare.  But put them together and…would you like a little salt on your salad?

Salt is electrical.  When sodium and chlorine atoms join to make salt, the chlorine pulls electrons off of the sodium.  The atoms become ions, electrically charged particles.  Salty water conducts electricity as the ions move toward oppositely charged poles.

To chemists, any compound of ions is a “salt.”  Table salt is only one particular type.  So if you’re at dinner with a chemist, be careful how you ask her to “please pass the salt.”

Pure sodium chloride forms clear cube-shaped crystals.  The crystals make look white because of little cracks made as the chunks of salt are crushed into smaller grains.  Colored salts—pink, black, blue, etc.—get their color from impurities, usually edible and tasty.

 

Where does salt come from?

Much of the salt we eat comes from the ocean.  There’s plenty of it there.  If all of the salt in the ocean were extracted it would cover the world’s total land mass to a depth of 35 meters.[1]

Sodium and chlorine ions aren’t the only types in seawater.  Others are magnesium, potassium, calcium, sulfide and bromide.  Taking an average of world’s oceans, every 100 pounds of seawater contain about 3.5 pounds of dissolved salts.   Almost all–about 90%–of these salts are sodium and chlorine ions.[2]

“Sea salt” is made by evaporating seawater.  To get really pure sodium chloride for our tables takes several stages.  For a description, click here.

“Rock salt” comes from natural deposits above and below ground. Salt companies mine it and crush huge chunks of it into smaller blocks.  Some companies dig into underground salt deposits, pump in water to dissolve the salt, collect the resulting brine (salt water) and purify the sodium chloride by evaporation[3]

 

What can salt be used for besides flavoring food?

Bleach, rubber, pharmaceuticals, plastics, glass, dyes, detergents—these are just a few of the many products made from salt.  Nearly 70% of all the salt produced in the world is used by industry to produce these and other substances, both familiar and not-so-familiar.[4]

Melting ice from roads, streets and aircraft uses tons of rock salt.   In 2017, highway de-icing alone accounted for 44% of the salt used in the United States.[5]

Salt preserves foods.  Lean fish like cod, dried then covered with salt, can last for months without rotting.  That pickle you pulled from a jar of brine, then ate, would have begun turning to slime within a week, had it been left as a fresh cucumber in your refrigerator.

 

Salt and Health

The average human body is about 0.4% common salt (sodium chloride) by weight.  That means that if you weigh 140 pounds, a little more than half a pound of that weight is pure sodium chloride.[6]

The sodium ions in salt are essential to the functioning of every cell in your body, particularly nerves, muscles, brain.  Without salt, you would not be able to think, speak, move, or even breathe.

How much salt should you eat?  It depends on your age, size, genes, the climate you live in, your level of activity, and possibly other factors.  United States Dietary guidelines usually recommend between 1500 and 2400 mg of sodium per day.  However, sodium is only one part of salt.  1500 mg of sodium corresponds to a little less than 4 grams of salt, or about ¾ of a teaspoon.  That measurement assumes you home-cook everything you eat and consume no sodium except as table salt.  But since it’s for the low end of the recommended range, it’s a reasonable guideline.  [7]

[1] http://www.maldonsalt.co.uk/About-Salt-Where-does-Salt-come-from.html. (accessed 9/17/13)

[2] https://oceanservice.noaa.gov/facts/whysalty.html

[3] http://www.saltinstitute.org/salt-101/production-industry/ (Accessed 8/15/2018)

[4] http://www.maldonsalt.co.uk/About-Salt-The-many-uses-of-Salt.html, (accessed 7/30/18)

[5] https://minerals.usgs.gov/minerals/pubs/commodity/salt/mcs-2017-salt.pdf, (accessed 7/30/2018)

[6]  http://www.sciencefocus.com/qa/how-much-salt-human-body.  (Accessed 7/30/18)

[7]Gunnars, Kris. “The Salt Myth – How Much Sodium Should You Eat Per Day?”  June 22, 2017.  https://www.healthline.com/nutrition/how-much-sodium-per-day (accessed 8/15/2018)