Geoscience Reference
In-Depth Information
Figure 3.29 Commercially available
autoclaves.
Source: Courtesy of M/S Toshin
Kogyo Co. Ltd., Japan.
volume, for the temperature of the next sample. As the whole procedure is highly
complicated and cumbersome, the sampling studies are done only in special cases,
when required. This is extremely useful in the solution speciation calculations to
know the regular changes in the chemical equilibria, pH, and so on.
Hydrothermal Autoclaves for Electrical Conductance Measurements
of Electrolyte Solutions
Although the electrical conductance of the dilute, aqueous electrolytes, was highly
desired in hydrothermal research in the early days, it was not popular among hydro-
thermal researchers owing to the lack of suitable autoclaves to work with such
provisions under hydrothermal conditions. The electrical conductance measure-
ments determine the extent of ionic behavior versus the association of a dissolved
aqueous electrolyte on the basis of conductance theory. It was not until early 1950s
that Fogo et al.
[72,73]
developed an apparatus and studied the conductivity of
aqueous NaCl solutions at temperatures up to 400
C and pressures to 300 bar.
They were the first to obtain the values of ionization constants of NaCl as a func-
tion of density in the supercritical region. Followed by this, Prof. E.U. Franck from
Gottingen, Germany, carried out the most pioneering research work from 1950s to
2000
[74
76]
. The other notable contributions are by T.M. Seward from ETH,
Zurich
[77,78]
, W.L. Marshall from Oak Ridge National Laboratory, USA
[79,80]
,
Ryzhenko and Smolyakov of Russia
[81,82]
, and Helgeson of USA
[83,84]
, who
not only popularized this field but also designed some novel autoclaves for such
studies.
Figures 3.30 and 3.31
show the schematic diagrams of the interior of a con-
ductance cell, and the conductance cell and electrodes developed by Quist and
Marshall which are in use at the Oak Ridge National Laboratory, USA, for studies
up to 800
C and pressure to 4 kbar. Though this vessel was initially designed by
