Sodium is a metal so unstable that it suddenly will burst into flame. By itself, chlorine is a poisonous gas. But together, they make sodium chloride, the salt with which we season our food and without which we cannot live.

“NaCl is from the only family of rocks eaten by humans,” writes Mark Kurlansky in his terrific book, “Salt: A World History.”

Try this at home: eat the salt rocks common to the kitchen or home and stimulate nearly all of the basic tastes available to your palate. Sodium chloride, of course, will juice up the “salty” preceptors. Potassium bitartrate, a by-product of winemaking and in most cooks’ pantries as cream of tartar, will tingle those that sense acidity or sourness. (It tastes as if you are sucking on a lemon wedge.)

A crystal of Epsom salt has an aftertaste of bitterness because that’s what magnesium sulfate, its proper salt name, does. And for that savory taste — the juicy, salivating, warming one — that we call “umami,” put a dab of MSG (monosodium glutamate) on the tongue.

Aha, so that’s why General Tso wins the food fights.

Stimulating the tongue’s awareness of sweetness, however, is perilous. The salt called lead diacetate will do that, but it’s commonly not at home, or shouldn’t be.

The history of salt

The sodium chloride that we so take for granted has been on our tables and counters only for a mere 100 or so years. For millennia before then, it was one of the most sought-after and precious commodities in our commercial and culinary history.

Wars were fought over it; people perished both for it and for lack of it.

We didn’t realize that there was so much of it around until geology and mining and cheap transportation made it ubiquitous. And we didn’t know it was so fancy — a funky, egg-smelling salt from Nepal, for example, or a pyramid-shaped one from Cyprus — until we “Bourdain-ed” our eating and dining out. All of that has been quite very recent.

Is salt important?

We need no more than 1,500 milligrams a day of salt, although most of us eat much more than that, around 3,400 mg daily according to the American Heart Association, and most of that from processed foods.

In the kitchen — not out of the can or package — we add salt to our cooking in myriad ways that we ought to note, for our own health’s sake. All of this is apart from and in addition to a pinch of salt from the shaker or saltcellar.

Take, for instance, the dressing for Caesar salad. Its anchovies, Parmigiano-Reggiano, Worcestershire sauce and, should you make it, a paste of crushed garlic and kosher salt, all add significant levels of salt to your plate.

Capers, bacon, many mustards or sauces such as soy and miso, and even simple and minimally processed foods such as canned tomatoes, again add salt to our cooking and diet.

Keep that in mind when you cook if you wish to monitor salt intake for yourself, your guests, or your family.

On the table

At a tasting of salts that I held recently, we noted that common table salt, the kind that pours out of a canister or shaker, is among the saltiest-tasting of salts available. A small amount of it on the tongue is nearly overwhelmingly salty.

Kosher salt brands themselves vary in salt intensity. They contain the same level or amount of sodium chloride (that’s because they’re just “salt”); it’s their method of delivery, however, that makes the difference in their “saltiness.”

Due to the way it is shaved, the light, hollow flakes of Diamond Crystal Kosher Salt taste much less salty — by a significant margin — than Morton Kosher Salt, the thin flakes of which are shaved differently. In a manner of thinking, the two kosher salts differ in how “thick” they are with salt. (Note: on the nutrition labels for both, a 1/4 teaspoon of the former delivers 12 percent of the daily value of sodium, while the latter delivers 20 percent of the same.)

Sea salts, so labeled or marketed, are more costly than table or kosher salt because they are harvested (mostly) by hand and via an evaporation process, and only during certain months of the year. Table and kosher salt, by and large, are mined in many places around the globe and in vast quantities year-round.

For cooking and eating, in addition to their obvious sodium chloride, I prefer to think of sea salts as points of texture. I like Maldon and Cyprus Flake because they stick around after the fire of the grill; chunks of “sel gris” in my salads or on my tomato slices are like adult Pop Rocks.

Cooking with salt

One final factor to keep in mind when using salt in cooking comes to play when you make mistakes with salt, something I’ve done many times myself.

It’s easy to over-salt; the culprit is salting too much too early, an easy screw-up. You cannot take the salt out, but you can try to balance it off with a squeeze of lemon or a splash of rice vinegar. The sodium chloride content doesn’t change, but the perception of it does.

Sugar (honey, cane sugar, and the like) plays the same trick on the tongue as acidity, if your recipe can handle it. Again, the salt level hasn’t changed, just the taste of it.

But the greatness of salt in cooking is what we all seek in its use: it “lifts” flavors, in enhances tastes. It makes all things savory.

Even the tears of error.

Salt-Baked Potatoes

Baking potatoes on a bed of salt gives spuds with crispy skin and (even using waxies) steamy, fluffy insides. Add whatever potatoes you might have in the bin; even mix russets and waxies, if you like. It helps if the potatoes (or potato chunks) are roughly the same size.

Ingredients

2 pounds (or more) potatoes

1 large 3-pound box kosher salt

4 tablespoons extra-virgin olive oil

1 tablespoon mixed dried herbs, crushed

1 tablespoon freshly ground black pepper

6-8 large peeled cloves garlic

Directions

Wash and dry the potatoes. In a large bowl, mix together the olive oil, herbs, and black pepper. In the mixture, toss the potatoes and garlic cloves, coating them well.

Heat the oven to 450 degrees. Pour the salt into a 9×13 baking dish or roasting pan, flattening the bed of salt out to an even depth (shake the pan or use the palm of a hand). Nestle the potatoes and garlic in the salt and cover the roasting pan with foil.

Roast for 45 minutes; remove the foil and roast for another 30 minutes uncovered, or until the potatoes are cooked through and very soft. Serve the potatoes and garlic cloves, shaking or scraping off any unwanted or excess salt.

Reach Bill St John at [email protected]