Hot water was passed over the feldspars contained in closed bombs, the total amount of solution weighed and analyzed, and the material remaining in the bomb studied with x-rays and the petrographic microscope. At 350°C, 5000 psi, the solution obtained from orthoclase and from albite contained over 90per thousand of the dissolved material in the feldspar ratio. At lower temperatures and pressures, 200°C, and 2000 psi, and 100° and 40 psi, albite was decomposed in greater proportion. At 350° and 2000 psi a large amount of analcime was found in the albite experiment, but none at the lower temperatures.