This paper represents the fruit of approximately 5 years of experimental studies at the Geophysical Laboratory. When Bowen and I were contemplating this study while I was still on the staff at the Naval Research Laboratory and he at the University of Chicago, the need for it was made apparent by some results on experimental studies on obsidian–H2O which I had carried out at the Geophysical Laboratory a few months before. The results were of great importance if equilibrium were attained, but of little significance if only metastability were involved (I had heated obsidian in the presence of water, and relatively large amounts, as much as 30 per cent, apparently went into the obsidian powder at approximately 500°C. and 30,000 psi.). As we had no knowledge of the effect of water on equilibrium relations in such compositions we decided to direct our efforts toward a study of the system NaAlSi3O8–KAlSi3O8–SiO2–H2O.). It was apparent that we would have to develop new experimental methods if we were to make progress in water-silicate mixtures. The hydrothermal quenching apparatus was therefore developed after many unsuccessful experiments with various types of pressure vessels then available.
Once the hydrothermal quenching apparatus was perfected we were able to begin studies on the granite-water system. As the three bounding binary systems were unknown we had first to study these. The NaAlSi3O8–KAlSi3O8–H2O) system was the first, and results of this and various papers dealing with polymorphism in the feldspars, which came as by-products of these studies, have been published. . . .