Studies of gas-solid equilibria. Part III.─Pressure-concentration equilibria between silica gel and (a) water, (b) ethyl alcohol, directly determined under isothermal conditions

Abstract

In this part of the work a thorough examination has been made of the pressure-concentration equilibria between silica gel and ( a ) water, ( b ) ethyl alcohol, at several temperatures, under strictly isothermal conditions and covering the whole range of concentrations possible. “Ascending” and “descending” pressure-concentration isothermals have been drawn from these direct measurements and the reversibility of the systems carefully investigated. The experimental procedure was exactly the same as that used and described in Part II of this work, except that the “cut-off” between the gel system and the calibrated reservoir was heated by a toluene vapour jacket instead of a steam jacket. In these and subsequent experiments the apparatus was constructed of Pyrex glass, with the exception of the calibrated reservoir which was made of ordinary soft glass and sealed to the rest by a graded Pyrex soft glass fused joint. All evacuations were carried out by means of a Gaede two-stage mercury vapour pump with a Gaede rotary oil pump as a backing pump. A McLeod gauge was included in the evacuating system.