Why is the freezing point of water 32F and not 0F?
Believe it or not, this was a question put to me by a colleague today. She had been asked by one of her children and did not know the answer. Neither did it – but I resolved to find out.
The short answer is that the Dutch-German-Polish physicist Daniel Gabriel Fahrenheit (1686–1736) chose to make the zero point of his scale the stable temperature of brine: a mixture of ice, water, and ammonium chloride at a 1:1:1 ratio. The second point, at 32 degrees, was a mixture of ice and water without the ammonium chloride at a 1:1 ratio. So, now you know.
If you’re interested in a bit more detail on how the Fahrenheit scale was constructed and evolved, you can find the information here.