Feb 2, 2009 This morning, my kids are listening eagerly to the
local radio to hear if their school will be closed? Why? Because
we’re in England, a few millimetres of snow has fallen, it’s a
little chilly, and the nation is in chaos. Airports are shut,
driving conditions are almost impossible, and schools are
closing across the country. The radio meteorologists are telling
us it’s the worst snow “event” since the early 1990s, although
it was worse almost exactly twenty years ago as I seem to recall
tramping to work in snow when I first moved to Cambridge.
Anyway, what has all this go to do with salt lowering the
freezing point of water? Well, The Highways Agency, which looks
after our main roads has had its fleet of gritter lorries spray
pink grit across the roads. So, what is it they’re spreading?
What is that grit? Well, it’s usually common salt, sodium
chloride, but calcium chloride is also used. Dissolving any
compound in another will lower its freezing point slightly. So
adding salt to water will lower i