The diëlectric constant measurement of powdered regular crystalline solids

Abstract 1. In measuring the D.C. of a powder a grain‐size effect must be taken into account. 2. For ε 1 /ε 2 ratio's up to 3 special precautions will not be necessary, for ratio's up to 6 the effect may be eliminated by using a large condenser (500 cm 3 ) and a powder of fine grain‐size (0.02 mm). 3. Former measurements of several authors cannot be relied upon, the grain‐size effect not having been taken into account. 4. Measurements of the D.C. of NaCl and KCl powder at different filling‐fractions under ideal conditions of powder‐sizes and of NH 4 Cl and KCl floating in CCl 4 ‐C 6 H 6 prove that the Böttcher and Wiener‐Bruggeman powder‐formulae give good results.