The determination of the piezo-electric moduli of ammonium seignette salt

Abstract
In a former paper the author compared the elastic properties of the two Seignette salts. It was shown that these properties were changed considerably on replacing the atom of potassium by the ammonium group. The ammonium salt, when subjected to tensile and torsional forces, was less elastic than the potassium salt, so that its deformation values were considerably increased. Other known differences were referred to, including the sizes of the unit cells, the change in optic-axial angles, with change in composition of the salts in “solid solution,” and the dextro- and lævo-rotation of polarised light for the two dextro salts in the directions of the optic axes. The potassium salt has pronounced piezo-electric properties. When a prism is pressed in certain directions with a pressure of one dyne per square centimetre, an electric moment of the abnormally large value of 1000. 10 -8 E. S. U. per unit volume is developed. It was therefore decided to determine the piezo-electric moduli of the ammonium salt and see the effect of the chemical change in the molecule and the associated piezo-electric change.

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