Question: By what mechanism does salt lower the boiling of water

Kamal Bhattacharya answered on 16 Jan 2017:

It raises the boiling point of water. So, there are two things, first, it boils at a higher temperature, second, it heats up faster. On the first one, water boils because its vapor pressure exceeds the ambient pressure. When you add salt, it is harder to create vapor pressure because you are essentially diluting the water with the salt. So the temperature will need to be higher than if you have water without salt to create enough vapor pressure for the water to boil.
On the other hand, by adding salt to water you are also decreasing the heat capacity of the water. Heat capacity is a measure for how much energy you need to increase the temperature of a substance by 1C. Water has high heat capacity as you can tell: it takes a while to boil water. Salt on the other hand has lower heat capacity. You mix’m up and you lower the heat capacity, hence, it boils faster but at a higher temperature than pure water. Fun stuff.

BTW you need over 250 g of salt in a liter of water to see an effect, so not sure it’s a great idea for cooking 🙂