Geoscience Reference
In-Depth Information
fluids from hydrothermal vessels. The hydrothermal experiments in these autoclaves
permit us periodic sampling at constant temperature and pressure, and total fluid
chemical analysis. If mineral buffers are used to constrain the activity of pertinent
aqueous species, these species should, if at all possible, be monitored directly to
determine the system and provide a means to evaluate buffer reactivity and equilib-
ria. Such studies have been carried out with excessively dissolved O
2
, and with
excessively dissolved H
2
and CH
4
, to evaluate reaction progress and equilibria in the
system Fe
3
O
4
a
H
2
O at 300
C and 500 bar. The dissolved
concentrations of several redox-sensitive species were periodically monitored
[66]
.
It is important to measure the total weight of the solution withdrawn from the
vessel, including both liquid and vapor phases. Partitioning of water from the liquid
to the vapor phase can significantly change the effective concentration of dissolved
solutes from their initial room temperature values. For example, a solution of 1 M
NaCl at room temperature would increase 10% in effective concentration to 1.1 M,
in a vessel at 350
C, half-filled with liquid, because of the water partitioned out of
the liquid into the gas phase. After each sample is taken, the salt and gas concentra-
tions must be recalculated for the effect of partitioning into the increased vapor
Fe
2
O
3
a
S
a
C
a
NaCl
a
Figure 3.28 Commercially available
autoclaves.
Source: Courtesy of M/S Toshin
Kogyo Co. Ltd., Japan.
Manometer
Druckmittler
Ventil
Berstscheibe
Temperaturfühler
Druckbehälter
Tefloneinsatz
