German physicist Gabriel Fahrenheit, in the early 18th century, called 32 degrees the freezing point of water. And 0 degrees on his scale represented the freezing point of what mixture?

To create a reliable temperature scale in the early 1700s, Daniel Gabriel Fahrenheit needed a consistent and reproducible zero point. He chose the coldest temperature he could achieve in his laboratory, which was produced by mixing equal parts ice, water, and a salt like ammonium chloride. This briny slush reaches a stable thermal equilibrium at a temperature far below that of freezing pure water. This phenomenon, known as freezing point depression, provided the reliable baseline that Fahrenheit designated as zero degrees on his new scale.

With this frigid mixture established as his zero, Fahrenheit then used other fixed phenomena to build out his scale. The next stable point was the freezing temperature of pure water, which he marked as 32 degrees. For a higher-end reference, he originally used the average human body temperature, setting it at 96 degrees. This system, based on three fixed points, allowed for a more precise range of measurement than previous scales. The boiling point of water, now famously set at 212°F, was standardized later, creating the familiar 180-degree interval between water's freezing and boiling points.