horizontal lines so that each one would intersect the stable portion of its respective activity curve at the same mole fraction. The values of the mole fraction, Nh thus obtained are 0.835 and 0.352. These values represent the compositions at which unmixing should occur.Inspection of these curves shows that only one pair of horizontal lines will satisfy the above conditions.Experiments are now in progress applying these methods to other solid solutions. It is hoped that extending the temperature range, especially in the direction of lower temperatures, will yield a more thorough knowledge of the nature of these solutions. Certainly, we would expect to find that any tendency toward the formation of compounds would become intensified with a decrease in temperature. Summary 1.The technique of making precise potential measurements of galvanic cells containing solid electrolytes has been described.2. The energy changes of solid silver chloride upon a dilution with sodium chloride have been determined at mole fractions of silver chloride varying from 1 to 0.160, between the temperatures of 150 and 230°.3. The course of an activity curve for a supersaturated condition has been followed experimentally over its complete range of composition.4. It is pointed out that Tammann's "limits of resistance" can be explained on the basis of this type of activity function.5. The existence of a regular arrangement of sodium ions in the silver chloride-sodium chloride lattice is verified.

The Ternary System Na2C03-NaHC03-H20 43 compression the arbitrary equations found to fit these curves are (F + 0.15) (A + 36.6) = 452 (I) (F + 0.15) (A -32.2) = 556 (II)From the "b" term in these two dimensional van der Waals equations we note that the ease of partial immersion of the chains varies inversely as the chain length, whereas the ease of immersion is about equal for the acid and neutral succinates (IV and V) of nearly the same chain length. The maximum pressure withstood by the films before collapse sets in does not vary appreciably with the chain length and is in the neighborhood oi 2.5 dyne/cm.

1725 SummaryThe compressibility isotherms of helium have been measured a t -70, -35, 0, 50, 100 and 200" up to 1000 atmospheres pressure.