This section summarizes the small amount of available data on solubility at high temperatures and pressures. Data are given for the solubility of solids in water (or water-rich solutions) and for the solubility of water in silicate melts. Emphasis has been on materials of geological interest, but a few substances which are uncommon in nature have been included. Little of the systematic experimental work has been on systems of a complexity approaching those to be found in nature.
With few exceptions the pressure was measured directly in the work reported here. No measurements of pressure were made in obtaining the data given in Table 19-12 and in some of the data in Table 19-7 . The approximate pressures given in Table 19-13 were calculated from the known volume of the bomb, using the steam tables for P-V-T data for water and the ideal gas law for CO2. Pressures of the mixture were calculated from Dalton's law. This approximation and the neglect of the effect of dissolved solids on the equations of state can introduce considerable error (See also section 17).
Several methods of determining the solubility of solids in an aqueous phase have been developed. The most accurate are either to withdraw a small sample from the reaction vessel and analyze it chemically, or to determine the loss in weight of a crystal or plate of solid after it has been equilibrated with a known amount of liquid. The first method requires that the sample be extracted in such