What was the thing that Hypatia of Alexandria invented to distill water called?
The hydrometer, which is used to measure the specific gravity of liquids. In 402 AD, the bishop Synesius of Cyrene sent a letter to Hypatia, asking her to construct a hydrometer for him. This is the first known reference to a hydrometer in history. It is not known when the hydrometer was originally invented.