TETRAETHOXYSILANE, SI(OC2H5)(4) - VAPOR-PRESSURE MEASUREMENTS AT TEMPERATURES FROM 323 TO 442 K BY MEANS OF A BOURDON SPOON GAUGE

The vapour pressure of tetraethoxysilane, Si(OC2H5)(4)(s,1), has been measured from 323 to 442 K and can be presented by the equation log(p/ Pa) = 37.5498 - 3940.10/(T/K) - 8.92951 . log (T/K). The boiling point derived from this equation is 441.3 K. The enthalpy of vaporization, Delta(vap)H(m)(o)(298.15 K), obtained by second- and third-law evaluat ion is -53.93 kJ . mol-1 and - 52.33 kJ . mol(-1), respectively. The r esult has been compared with literature data and the value, Delta(vap) H(m)(o)(298.15 K) = (52.0 +/- 2.0) kj . mol(-1), is recommended for th e enthalpy of vaporization of tetraethoxysilane. Combining this value with the enthalpy of formation of liquid tetrathoxysilane results in D elta(f)H(m)(o)(Si(OC2H5)(4), g, 298.15 K) = -(1356.0 +/- 6.0) kJ . mol (-1).