Abstract: The invention relates to a method for determining at least one property of hydrocarbon fluid, comprising: (a) providing a first chamber (1) filled with the hydrocarbon fluid and a second chamber (2) which is substantially empty, each of the first chamber (1) and second chamber (2) having a fixed volume; (b) transferring a sample of hydrocarbon fluid from the first chamber (1) to the second chamber (2); (c) measuring a pressure in at least one of the first chamber (1) and the second chamber (2); (d) repeating steps (b) and (c) a plurality of times. The invention also relates to an apparatus for implementing this method.