Achieving Absolute Negative Pressures in Liquids: Precipitation Phenomena in Solution

Abstract

A relatively simple and inexpensive experiment to achieve absolute negative pressures in liquids is reported. The liquid is a 1.80% (w/w) solution of polystyrene (Mw = 25,000) in acetone. A detailed description of the experiment is followed by photographs, one of which shows a phase transition occurring at negative pressure. By repeating the experiment at different initial volume ratios of liquid to gas, several phase transition points (cloud points) at distinct negative pressures are determined. For each run, the achieved negative pressure is estimated using the isochoric thermal pressure coefficient γV. To test the reliability of the experimental data, they are compared with data obtained in the positive-pressure region using a different, more precise technique. The two sets of points match reasonably well.