How salt gets rid of ice — and why it doesn’t always work

Sodium chloride, otherwise known as salt, won't get rid of ice if the temperature dips below 15 degrees

salt snow road generic

YOUNGSTOWN, Ohio (WKBN) – After weeks of winter weather, salt is everywhere. It covers the roads and walkways but every day, it seems like we need to add more. However, on some days, salt will not work and you’re just wasting your time and money.

Sodium chloride, otherwise known as salt, helps to get rid of the ice and keep us from slipping. Over 20 million tons of it is used on roads in the U.S. each year.

Crews in the Youngstown area have been out for weeks, salting and treating the roads. But the Ohio Department of Transportation knows it needs more than just salt during winter’s cold snaps.

“We are constantly putting down some salt and some other products that we use in colder temperatures,” said Brent Kovacs, with ODOT.

It’s the colder temperatures that create a problem.

“We use sodium chloride because it’s cheap and abundant but sodium chloride is effective to about 20 to 15 degrees Fahrenheit,” said YSU Biochemistry Professor Dr. Michael Serra. “If it gets colder than that, it really doesn’t work.”

For example, if it’s 30 degrees outside, one pound of salt will melt 46 pounds of ice. But if the temperature drops to 5 degrees, that one pound of salt will only melt 4.5 pounds of ice.

It creates a nightmare for us but road crews are ready.

Serra said salt lowers and raises the freezing and boiling points of water. So when you see the ice disappearing, it’s not because the salt is melting it.

“What it does is that it lowers the freezing point so it has to get colder before water freezes,” Serra said.

When our low temperature dips below that new freezing point, the water can turn back over to ice. This is why additives, like calcium chloride, are used on the roadways.

“Calcium chloride is effective up to -60,” Kovacs said.

For the rest of us who aren’t able to use the high-powered chemical, there is still hope.

“Even if the sodium chloride — which is mostly what we are using when we throw it out on the sidewalk — if nothing else, it provides traction,” Serra said. “So even if it’s not very effective at incredibly cold temperatures we’ve had recently, it provides some traction.”


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