What Is the Difference Between Road and Table Salt?

(Last Updated On: July 1, 2019)

What Is the Difference Between Road and Table Salt?

The Difference Between Road and Table Salt

Okay, so you want to know the difference between road salt and table salt. Well, there’s one key difference–you should definitely avoid eating one of them!

That said, some of our more astute readers might already know that both road and table salt are sodium chloride. This might suggest they are actually the same, but not quite.

First off, there are some preparatory differences. Normally table salt is made via solution. Either from the sea, or water. Yes, sometimes your table salt is made by evaporating sea water and collecting the salt left behind (and then purifying it).

There’s also a technique known as “solution mining.” That whole process is a can of worms that’s also used to do other things (like recover uranium). But the long short is you take water and blast it at solid salt formations, which dissolves the salt (since salt is soluble in water). Then you collect the solution with your water and salt, dry and purify that, and you get table salt. 

Road salt (aka rock salt), conversely, can be mined dry by just hacking it out of the Earth. Which is probably why it’s called rock salt. But, by this logic, could you just purify your road salt some more and use it in your next meal? Do not do that. That would be a terrible idea. That’s because ferrocyanide is added to road salt to keep it from clumping together and becoming useless in storage. You don’t really need to know more about ferrocyanide other than “it’s really bad for you.”

Why Does Salt Melt Ice?

So how does salt actually cause ice to melt? It’s pretty simple, actually.

In essence, salt makes it harder for water to freeze. But road salt won’t work if the ice is 100% solid. Almost always, however, road ice will have a layer of water on top of it, in contact with the air. When salt is added, it dissolves and makes a solution with the water that is present, which now cannot refreeze. This process continues until the salt’s all liquid.

If you want to get into some of the more advanced physical chemistry we’ll give you a quick briefing. Basically when water freezes, the water molecules come together to make a repeating lattice structure. Salt, as we’ve already discussed, is soluble in water. So now you have both sodium and chloride ions floating around in water that’s trying to freeze. These extra ions more or less get in the way of the water molecules trying to make the lattice structures, therefore making the freezing process require a lower temperature. Thus, road salt helps melt snow.

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About Kyler 706 Articles
Kyler is a content writer at Sporcle living in Seattle, and is currently studying at the University of Washington School of Law. He's been writing for Sporcle since 2019; sometimes the blog is an excellent platform to answer random personal questions he has about the world. Most of his free time is spent drinking black coffee like water.