The most official water costs $120k a gallon
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- Water freezes at 0°C, but isotopic composition (hydrogen and oxygen isotopes) affects the freezing point.
- Hydrogen has protium, deuterium, and tritium; oxygen has oxygen-16, -17, and -18.
- Heavier isotopes like deuterium and oxygen-18 raise the freezing point to about 4°C.
- Natural isotope ratios vary; rainwater is lighter than ocean water due to evaporation rates.
- Vienna Standard Mean Ocean Water (VSMOW) was established as the international standard for metrology.
- VSMOW's triple point (0.01°C) was the basis for the Kelvin scale until 2019 and is used to calibrate precision thermometers.