Too Cold to Melt

Admittedly, I delayed the hour of my walk today in favor of a higher temperature. But even at 11am, even as the sun’s rays reflected brilliantly off the snow, the thermometer read “11.” And a local observation station said it went down to 6 degrees last night.

Six? That’s under the threshold in which salt (sodium chloride) no longer melts ice.

Here in Pennsylvania, road crews (under pressure from the public) use a frivolous amount road salt. Much suffers as a result (cars, fish, plants, streams, road surfaces) but that’s a topic for a much longer essay.

A pile of road salt spilled at an intersection, the rest of the road turned white with salt.
A pile of road salt spilled at an intersection, the rest of the road turned white with salt.
Small piles of road salt found all along the way.
Small piles of road salt found all along the way.

Instead, today’s post is about science. The concentration will make a difference, but it’s safe to say that salt won’t liquify ice when the air temperature is under seven degrees. Road crews tend to use 15 as a threshold.

So be careful out there. Standing moisture, unless treated with something other than salt, could be frozen into “slipperyness.” It’s all a matter of degrees.

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