Chemical of the Day: Salts!
When hearing the word 'salt', most people think of table salt. Or maybe road salt.
But ask a chemist, and salt is "ANY chemical compound formed from the reaction of an acid with a base, with all or part of the hydrogen of the acid replaced by a metal or other cation".
A salt is an ionic compound which is made up of two groups of oppositely charged ions. The ion with a positive charge is called a cation, and the one with a negative charge is called an anion. We won't dive too deeply into what all that means, but here's a picture of various salts to visually illustrate the point that 'salt' means more than just our familiar friend Sodium chloride (a.k.a., table salt), the fourth salt pictured. Who knew 'salt' could be blue or green?
Although salt is most familiar as a food additive/supplement, less than 5% of the salt produced in the United States is used for that purpose. About 70% is used in the chemical industry, mostly as a source of chlorine. Salt is also used for countless other purposes, such as removing snow and ice from roads, softening water, preserving food, and stabilizing soils for construction.
SALTS IN SOAPMAKING
Salts are also used in the formulation of cosmetics and personal care products. As a matter of fact, making true soap would be impossible without a salt! Soaps are sodium or potassium salts of long chain fatty acids (as in coconut oil, palm oil, shea butter, etc.). When triglycerides in these fats/oils react with potassium hydroxide or sodium hydroxide (also called lye), they are converted into soap and glycerol. Since this reaction leads to the formation of soap, it is called the saponification process. Liquid soaps are made with potassium hydroxide, and hard soaps (like bar soaps) are made with sodium hydroxide. So, no matter how 'pure, natural, and organic your soap is', it's still made with one of these guys (yes, even Dr. Bronner's):
But don't worry; none of these two chemicals remains in the soap after the saponification process.
Dendritic Salts, also known as crystalized salts, are sodium chloride just like table salt is but with a different structure. Dendritic Salts are processed into a kind of crystal structure making them able to surround, encapsulate, and trap fragrance within itself. This slows down the evaporation rate of fragrance. Dendritic salts also reduce caking. Dendritic Salts are the secret to making bath salts. In both handcrafted and conventional products, salt is listed as simply 'sodium chloride' on the label, but this is the 'secret ingredient' that makes for free-flowing salt with scents that last. Bath salts do not hold fragrance very well without the use of dendritic salts or other additives.
Epsom salt is magnesium sulfate heptahydrate, usually shortened just to magnesium sulfate, and it was originally obtained by boiling down mineral waters at Epsom, England.
So, why do people say 'Epsom salts' with an 's' sometimes? It’s really just one kind of salt, and other than tradition there’s no more reason to say “salts” than there is to say “please pass the table salts.” It's sold over the counter as a laxative and as a bath additive for reducing muscle soreness. Here's a fascinating discussion about the science (or lack thereof) about Epsom salt's effectiveness at relieving pain: https://www.painscience.com/articles/epsom-salts.php. Is it just the hot bath that's really working here, and any pain relief from Epsom salt is a placebo effect? Read on!
SEA SALT VERSUS TABLE SALT
Ever heard of 'solar salt'? (Me neither!) Solar salt is another name for the more familiar sea salt) . What's the difference between sea salt and, say, Morton's in the blue canister?
Depending on who you ask, there's really no difference at all, or all the difference in the world!
Technically speaking, all the salt you're seeing on store shelves is 'sea salt'. Yup, even Morton! The difference is what we call table salt is typically mined from salt deposits, remnants of older bodies of seawater that have since dried up and are long gone, while 'sea salt' is crystallized from current bodies of seawater, either by open-air solar evaporation (usually more expensive sea salts on the market come from this evaporation method) or by a quicker vacuum evaporation process.
Table salt is processed to purify and strip it of all other minerals and contaminants, and then supplemented with anti-caking substances, such as sodium aluminosilicate, silicon dioxide, and magnesium carbonate. Sea salt is either sold as unrefined or refined. The unrefined sea salt is unwashed and therefore may appear grey in color from sediment and clay impurities. Unrefined sea salt is also coated in trace minerals, algae, and even marine bacteria that can tolerate high levels of salt. All these may contribute to a more complex flavor. On the other hand, refined sea salt is washed to strip it of its trace minerals and clay/sediment contaminants, purifying it into a salt that is just like table salt.
Sea salt, table salt, kosher salt, flavored salt, fleur de sel, Hiwa Kai, Black Hawaiian Sea Salt, Kala Namak, “organic salt,” and "Pink Himalayan" Sea Salt - so many different kinds of salt! They're all basically the same chemical, though: sodium chloride. However, trace amounts of other substances can vary, and gourmet chefs swear by the taste differences of these different salt varieties.
It's a little bit weird to hear any salt referred to as 'organic', as sodium chloride is an inorganic compound. Put in simplest terms, organic compounds have at least one carbon atom, while inorganic compounds do not contain carbon (there are a few compounds classified as 'inorganic' that actually do contain carbon, but that's outside of the scope of this blog post!)
The way the word 'organic' is used in marketing is different than the way the word is used in chemistry, however. When it comes to salt marketing, "organic" usually means 'made without additives like iodine or anti-caking agents".
Let's clear up one more misconception while we're at it: there's really no such thing as 'Himalayan Salt' - like 'organic salt', it's just another marketing term. There are no salt mines in the Himalayas. 'Himalayan' salt is mined from the nearby Salt Range foothills. The full Salt Range stretches across the entire Punjab province, covering about 300 kilometers. Although it contains a number of different salt mines, Khewra is the only one that produces true Himalayan salt. I guess "Himalayan salt" sounds more romantic and intriguing than "Punjabi region salt"?
People who claim unrefined sea salt (especially Himalayan salt) has health benefits usually point out the minimal processing, the improved flavor, and the health benefits of the trace minerals left in the salt. Naysayers claim that chemically, sea salt and table salt are virtually identical, and that purported health benefits are just a marketing strategy to charge outrageous prices for something that's otherwise very cheap. Read more here:
Himalayan sea salt is hippie-dippy woo woo: https://badscidebunked.wordpress.com/2016/01/18/your-worst-day-ever-david-avocados-himalayan-salt-debunked/
CONCLUSIONS AND FURTHER READING
We mainly focused on salts used in food preparation and in personal care products, but there are many other uses of salts, too - like road salt!
Do some further reading to form your own opinion on the debate about whether the benefits of unrefined sea salt justify the higher prices, and whether or not a salt lamp just looks pretty or actually has health benefits. Another interesting topic to research is whether or not advising Americans to drastically cut sodium intake improves health outcomes - there's some strong debate on this issue.
Salt is a fascinating subject, both chemically and historically!
RESOURCES ON THE WEB
How Salt is Made?: http://www.madehow.com/Volume-2/Salt.html
Does Epsom Salt work? https://www.painscience.com/articles/epsom-salts.php
Sea Salt versus Table Salt: Is there actually a difference? https://www.thekitchn.com/sea-salt-vs-table-salt-is-there-actually-a-difference-221471
David Avocado's Himalayan Salt Debunked: https://badscidebunked.wordpress.com/2016/01/18/your-worst-day-ever-david-avocados-himalayan-salt-debunked/
All About Salt: https://www.thoughtco.com/all-about-salt-1441186
Salt, a World History. https://www.amazon.com/Salt-World-History-Mark-Kurlansky/dp/0142001619
The Story of Salt (children's book): https://www.amazon.com/Story-Salt-Mark-Kurlansky/dp/0147511666/ref=sr_1_2?s=books&ie=UTF8&qid=1515607829&sr=1-2&keywords=history+of+salt