|Why did Fahrenheit choose 32° for the freezing point of water and 212° for the boiling point of water? These seem like such awkward numbers to use.
Daniel Gabriel Fahrenheit chose as the zero of his temperature scale the temperature at which ice melts when it's mixed 50/50 with salt. He then set the temperature at which pure ice melts to be 30° above zero and normal body temperature to be 90° above zero. These values were adjusted several times over the years as temperature measurements became more accurate and are now 32° and 98.6° respectively. Having established the temperature scale based on these various situations, he had no choice about water's boiling temperature. Water's boiling temperature at normal atmospheric pressure simply turns out to be roughly 212° on his temperature scale.