Saturated Vapor Pressure Measurements for Tetraethyl,\nTetrapropyl, and Tetrabutyl Orthosilicates up to 473 K

The\nsaturated vapor pressures of tetraethyl orthosilicate (TEOS,\n(CH<sub>3</sub>CH<sub>2</sub>O)<sub>4</sub>Si), tetrapropyl orthosilicate\n(TPOS, (CH<sub>3</sub>CH<sub>2</sub>CH<sub>2</sub>O)<sub>4</sub>Si),\nand tetrabutyl orthosilicate (TBOS, (CH<sub>3</sub>CH<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>O)<sub>4</sub>Si) were measured at temperatures\nup to 473 K using an apparatus based on the general static method.\nThe standard uncertainties (<i>u</i><sub><i>s</i></sub>) were <i>u</i><sub><i>s</i></sub> (<i>T</i>) = 0.029 K and <i>u</i><sub><i>s</i></sub> (<i>p</i>) = 0.015 kPa, and the maximum combined\nexpanded uncertainties <i>U</i> (0.95 level of confidence)\nwere <i>U</i>(<i>T</i>) = (0.52, 8.60, and 1.64\nK) and <i>U</i>(<i>p</i><sup>sat</sup>) = (2.81,\n3.09, and 0.82 kPa) for TEOS, TPOS, and TBOS, respectively. Furthermore,\nthe saturated vapor pressure was correlated using the Antoine equation\nto determine its parameters. The measured saturated vapor pressures\nwere correlated with previously reported pressure–volume-temperature\ndata using the PC-SAFT equation of state (EoS), followed by optimizing\nthe pure component parameters of the PC-SAFT EoS. A relationship between\nthe molecular structure and component parameters was identified, and\nthe occupied volumes were determined according to the Sanchez–Lacombe\nand PC-SAFT EoS, revealing significant differences. Our findings highlight\nthe potential of using the molecular structure to predict pure component\nparameters. In addition to providing accurate vapor pressure data\nfor these orthosilicates, this study offers insights into correlation\nmethods, emphasizing the importance of parameter determination in\nequation of state modeling.