Abstract: The invention concerns a method whereby a fluid sample is brought (1) at constant pressure Pe and temperature maintaining the heavy fractions, in particular asphaltenes, in dissolved state and/or in stable colloidal state, at the intake (4) of a capillary passage with high pressure drop. Said sample is forced to flow through the capillary conduit, at an increasing flow rate. The method consists in measuring (11) the fluid pressure Ps and the fluid flow rate D (12) at the outlet (5) of the capillary conduit and in representing the variation curve of the quantity &Dgr;P=Pe−Ps or the quantity D as a function of the other quantity or as a function of time. The deposit pressure, characteristic of the threshold of deposit of heavy fractions, is defined as the value of pressure Ps, which corresponds to a change of the slope in the variation curve of the quantity &Dgr;P or the quantity D.

Abstract: An ebulliometric device measures with high precision a physical parameter of a liquid substance. It includes an ebulliometer having an elongate vessel into which a liquid substance is fed, a sensor for measuring the boiling-point temperature arranged in the upper part of the vessel, a pump allowing to spray substance in the form of liquid and vapor in the upper part of the vessel, and an assembly external to the vessel for condensing the vapor allowing to recycle the condensed vapor to the base of the vessel and at least one thermostat-controlled enclosure.

Abstract: A system for measuring the solubility of various solid organic compounds in supercritical fluids such as methane or carbon dioxide for example, and for studying the equilibrium between the solid phase and the supercritical phase in a wide pressure and temperature range is disclosed. The system comprises four functional units E1, E2, E3, E4. Unit E1 delivers a supercritical fluid (methane, CO.sub.2, etc.), unit E2 comprises a sampling cell containing the compound to be solubilized, where the pressurized gas from unit E1 saturates on contact therewith, unit E3 is intended for sampling and bringing the sample into solution, and unit E4 is intended to receive the saturated fluid and to analyze it. The system allows dynamic solubilization to be performed with on-line or off-line analysis of the sample. The system can be applied for production of very pure compounds isolated from mixtures of heavy hydrocarbons for example or from alloys, or in the agribusiness for isolation of flavors.