The solubility and transfer of silica and other non-volatiles in steam

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Abstract
Recent experiments show that several non-volatile substances are appreciably soluble in supercritical steam at pressures above 200 kg/cm 2 . Steam at 450 degrees C and 304 kg/cm 2 dissolves 240 ppm of silica from gel. Higher pressures caused by rise in temperature increase solubility. Also, at constant temperature solubility increases with rise in pressure.By placing various oxides or carbonates in platinum crucibles near the top of a steel bomb and water and silica gel in the bottom, silica is transferred through steam at a rate which increases with pressure and which is dependent upon the "reaction potential" between silica and the substances in the crucibles.Kaliophilite, muscovite, pyrophyllite, wollastonite, serpentine, forsterite, brucite, and talc were synthesized. Wollastonite was formed by transfer of silica to Iceland spar. Silica and magnesium oxide formed serpentine and brucite when the temperature was below about 435 degrees C and forsterite and brucite when the temperature was higher. At 522 degrees C and about 650 kg/cm 2 talc and forsterite were obtained. In experiments involving temperatures above 450 degrees C the silica gel frequently altered to euhedral crystals of quartz. If this happened, transfer would be very much slower on account of a lowered reaction potential.It may be concluded that steam at pressures above 300 kg/cm 2 is a powerful solvent of nonvolatiles such as silica. Pressure may be almost as important as temperature in the formation of mineral deposits by emanations.

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