A NEW DEVICE FOR EXPANSIVITY MEASUREMENTS OF LIQUIDS AT HIGH-TEMPERATURE AND PRESSURE AND EXPANSIVITY DATA FOR LIQUID-TIN TO 1450-DEGREES-C

We have developed a new technique for measuring thermal expansion of l iquids at high temperature. Our device, the volumeter, is a volumetric dilatometer which uses liquid tin to transmit volume changes to a ser ies of electrical contacts. Measurements can be carried out from 250-d egrees-C to at least 1450-degrees-C irrespective of the viscosity of t he sample. In addition, our technique allows for the direct determinat ion of volume changes due to melting and crystallization, as well as t he volumetric properties of heterogeneous mixtures of materials. Furth ermore, the device is designed to operate inside an internally heated gas-pressured vessel, allowing for the determination of compressibilit y. We have measured the thermal expansivity of tin from 435 to 1445-de grees-C. Our data match previous measurements using the Archimedean te chnique to within 4% and shows the volumetric expansivity of tin to ha ve a temperature dependence of -4x10(-9)degrees-C-2. Preliminary measu rements of the thermal expansivity of a high-viscosity silicate liquid show a wide degree of scatter but fall within previous estimates base d on density data. Improved performance of the device may require its operation under pressure.