Saturated liquid densities and vapor pressures of tetramethyl orthosilicate measured using a constant volume apparatus

This paper describes a simple constant volume technique that was developed to measure saturated pressure and saturated liquid density of tetramethyl orthosilicate (TMOS). The technique is based on the measurement of temperature and pressure of a liquid undergoing a constant volume heating process. We have observed that during such a process the pressure increases gradually as temperature is increased until the system reaches a "take-off" point where a rapid pressure rise occurs. Experimenting with methanol and water, we determined that the initial pressure/temperature data (pre take-off) can be used to estimate saturation pressure. We further determined that the take-off point occurs when the liquid expands to fill the container volume, which allows for calculation of the saturated liquid density. Using this information, we estimated and report on the saturated pressure and saturated liquid density of TMOS for temperatures from (60 to 250) degrees C.