The microdetermination of H 2O, CO 2, and SO 2 in glass using a 1280°C microscope vacuum heating stage, cryopumping, and vapor pressure measurements from 77 to 273 K

Abstract

A new microscope vacuum heating stage and gas analyzer has been developed for measurement of H 2O, CO 2, SO 2, and noncondensable gas (H 2, CO, N 2, Ar, CH 4, etc.) evolved from samples, particularly natural glass, at temperatures up to 1280°C. The gas evolved upon heating to 1280δC is collected in a liquid nitrogen cold trap. Gas components are identified by the characteristic vapor pressure and temperature ranges over which solid and vapor are in equilibrium during sublimation of individual components. The masses of CO 2, SO 2, and H 2O derived from samples and blanks are calculated using the ideal gas law, the molecular weights of the components, and the gauge constant (i.e. the ratio of the number of moles of a gas to its partial pressure in the constant volume). Results obtained by repeated determinations of H 2O, CO 2, and SO 2 evolved from a submarine basaltic glass from Kilauea volcano, Hawaii, (average sample mass = 3 × 10 −3 g) gave probable errors for the determinations of H 2O (0.23%), CO 2 (0.025%), and S (0.071%) equal to 4, 10, and 8% respectively, of the concentrations. Determinations of H 2O in smaller samples of H 2O-poor basaltic pumice show a linear proportionality (0.063%) between the measured H 2O and the sample mass over the range 0.1 × 10 −6 to 1.7 × 10 −6 g H 2O. Comparisons of H 2O determinations by this technique with those obtained by Penfield, gas chromatic, microcoulometric, and vacuum fusion techniques used elsewhere show reasonably good agreement. Determinations of SO 2 by this technique agree reasonably well X-ray fluorescence and electron microprobe determinations of sulfur. Determinations of CO 2 by the present technique are reproducible but cannot be compared directly to measurements made in other labs because of differences in samples analyzed. The principle advantages of this analytical technique are the very small sample required, the simultaneous determination of H 2O, CO 2, SO 2 and noncondensable gas, the avoidance of calibration procedures dependent on chemical standards, and the visual observations that can be made during sample outgassing.