I. On electrostriction

Abstract

If the bulb of an ordinary thermometer be coated chemically with silver, and then electrically with a metallic deposit, the mercury will traverse some portion of the scale, and finally take up a definite posi­tion, independently of temperature. To this phenomenon I have given the name electrostriction . Of the metals hitherto worked with, copper, silver, iron, and nickel constrict the bulb; zinc and cadmium distend it. The general conditions under which the experiments were made were as follow:—A thermometer coated with silver by immersion in a solution of ammoniacal argentic tartrate was placed vertically near a bare ther­mometer at one side of a depositing cell; the anode stood at a distance of 11 centimetres. The bulbs of the thermometers were about their own depth below the surface of the electrolyte; the covered one was turned half round at every comparison. The source of electricity was a pint Daniell’s cell, having a porous diaphragm, and the circuit included a galvanoscope. Observations were made at definite intervals of time, imme­diately after stirring the liquid; and the difference between the two scales, after suitable reduction, was registered as electrostrictive effect. The temperature was in all cases the unrestricted temperature of the labo­ratory.