11. The Fahrenheit hydrometer is a constant-volume device that will float in water. 12. However, the hydrometer was invented before Hypatia, and already known in her time. 13. In Synesius'fifteenth letter, he requests Hypatia to make a hydrometer for him. 14. This is because the change in air pressure is applied to the entire hydrometer flask. 15. The hydrometer transformed how beer was brewed. 16. Similarly, the hydrometer was invented before Hypatia, and already known in her time. 17. The hydrometer is then floated in a liquid of unknown density ( shown in green ). 18. Certain ships of the United States Navy adopted the use of the hydrometer in the 1850s. 19. Soil gradation is determined by analyzing the results of a sieve analysis or a hydrometer analysis. 20. One danger of these built-in hydrometers : They check only one of the six cells.
