Method of determining cloud points and cloud point meter

摘要

A method of determining cloud points is provided which comprises: bringing a sample into contact with a high precision cloud point meter which includes a waveguide sensor of a total-reflection type connected to both incidence and emergence optical fibers and a cooling/heating means located in contact with the total-reflection type sensor to cool/heat it within a desired temperature range; cooling/heating the sample; and then determining the sample temperature at which total-reflection of light has taken place as the cloud point of the sample. The sensor includes a waveguide of a structure which consists of an incidence channel and an emergence channel formed on a substrate and which intersect along a detection surface with which a liquid whose cloud point is to be determined comes in contact. An incidence optical fiber is connected to the entrance of the incidence channel to introduce of light into the channel, and an emergence optical fiber is connected to the exit of the emergence channel to receive total reflected light from the channel. Alternatively, a waveguide is formed which comprises an incidence region and an emergence region both of which are adjacent to the detection surface, and an incidence channel intersecting the incidence region and a plurality of emergence channels intersecting the emergence region. The cooling/heating means is preferably a Peltier element mounted on a heat sink.