Most of us might like snow and ice, but we must admit that it doesn’t make transportation from one place to another easy when it fills up the roads. Do you know which kitchen ingredient helps those involved perform the task of clearing such roads?
De-icing trucks in places where the phenomenon is common spray rod salt on highways, streets and footpaths to melt the ice. Yes, you read that right. Road salt, which is in fact halite or rock salt, is the natural form of table salt. While table salt goes through a purification process, rock salt does not and hence retains impurities, giving it its gray-brown colour.
Freezing point depression
You know that ice forms when the temperature of water reaches 0 degrees Celsius and it is no different with the ice that forms on roads. Rock salt works because it lowers the freezing point of water by a process called freezing point depression.
A 10% salt solution freezes at 6 degrees Celsius and a 20% solution freezes at -16 degrees Celsius. Thus, even a small amount of salt significantly makes it more difficult for the water to freeze.
Brine solution
There is another point to be kept in mind during this process though. For freezing point depression to take place, there should be at least a little bit of water on the roads. It is for this reason that when there is a forecast of snow and ice, trucks pre-treat the roads with brine solution, which is a mixture of water and salt. The pre-treating ensures that a lot of ice isn’t formed, which, in turn, implies that a lot of de-icing trucks will not be required.
The technique isn’t without its flaws as well. Rock salt has its own limits in terms of the temperatures at which it works. There are also environmental concerns based on impurities that it holds, apart from the sodium and chlorine. These can latch on to the ground where it is sprayed and the groundwater below as well. Rock salt, however, remains the most popular, widely used and affordable de-icers available.
Picture Credit : Google