Patent ID: 7338203

Claim:
A method of analyzing a sample, comprising the steps of: providing an apparatus, comprising: a laser emitter and an associated longitudinal optical receiver mounted on either side of a horizontal tubular measuring cell located in a cryostatic chamber equipped with a temperature sensor connected to cooling and temperature control members, so that an optical beam emitted by the laser emitter is aligned with a longitudinal axis of the measuring cell and with the longitudinal optical receiver, and wherein the temperature sensor, the cooling and temperature control members and the longitudinal optical receiver are connected to programmable calculating and display means; a diaphragm mounted directly downstream of the laser emitter, the diaphragm reducing a cross section of the optical beam to prevent reflection of the optical beam on the walls of the measuring cell; a polarizer mounted upstream of the longitudinal receiver, the polarizer oriented such that the optical beam initially emitted by the laser emitter cannot be transmitted therethrough; and a lateral optical receiver mounted proximate to an upstream portion of the measuring cell, the lateral optical receiver connected to the programmable calculating and display means and receiving the optical beam emitted by the laser emitter; obtaining a sample; introducing the sample into the measuring cell; activating the laser emitter, the longitudinal optical receiver and the lateral optical receiver to pass an optical beam through the sample; gradually lowering the temperature of the cryostatic chamber while recording a detection curve showing the variations in light intensity received by the longitudinal optical receiver as a function of the temperature, and an opacity curve showing the variations in the light intensity received by the lateral optical receiver as a function of the temperature; determining, using the opacity curve, at least one of the end of crystallization temperature and the point of opacity of the sample; gradually raising the temperature of the chamber while continuing to record the detection curve and the opacity curve; and determining the vanishing point of crystals in the sample from the detection curve within a temperature range of −5 to −120° C.