Photoelectrons and Negative Ions.

A SUMMARY of the results of an experimental research concerning the formation of negative ions from electrons may prove of interest. The electrons were generated by means of light emitted from a quartz mercury vapour lamp (`Home Sun' D.C. type) and incident upon a gold-plated electrode distant 2 cm. from a similar electrode. Between these two electrodes an alternating potential difference of `square' wave form was established. During a fraction (ƒ) of the time of a complete cycle the electric carriers advance to the receiving electrode; in the remainder of the cycle their motion is reversed, and they are withdrawn from the gas. The gas contained in the measuring vessel was air at various pressures; no purification of the air was attempted other than careful drying.