Source of a Continuous Ultraviolet Spectrum.

W. H. Fulweiler and J. Barnes. A Source of Light giving a continuous spectrum in the ultra-violet. Journ. of Francl. Inst., V. 194, No. 1, p. 83, 1922.

The authors use, for obtaining a continuous ultraviolet spectrum, a spark under water between tungsten electrodes. Electrodes of aluminum, brass, iron, nickel, carbon, and molybdenum had previously been tested, but tungsten electrodes gave much shorter rays in the ultraviolet region, require the simplest apparatus, and the spectrum obtained is completely homogeneous, without bright bands and lines. The $Wo$ electrodes had a diameter of 3.5 mm; the length of the spark gap was about $1/2$ mm. The spark passed in water flowing inside a glass vessel of about 500 cm³ capacity. The radiation emerged through a quartz plate inserted at the end of a brass tube entering the vessel and standing 1 cm from the spark.

The spark was supplied from a 1.6 kw. X-ray transformer with a mercury interrupter (110 V. and 15 amp.); the secondary winding was shunted by two Leyden jars of 0.001 mf, connected in series. In series with the spark between the $Wo$ electrodes there was inserted a spark gap between $Zn$ electrodes, blown with air. The $Wo$ electrodes disintegrated very slowly in comparison with $Al$ and seldom required adjustment.

The continuous spectrum obtained between the $Wo$ electrodes extends to 205 mμ.

C. Rzhevkin.