On the production of transparent metallic film by the electrical discharge in exhausted tubes
1877; Yale University; Volume: s3-13; Issue: 73 Linguagem: Inglês
10.2475/ajs.s3-13.73.49
ISSN1945-452X
Autores Tópico(s)Vacuum and Plasma Arcs
ResumoTHE spectra of gases contained in vacuum-tubes, which have .beenprepared by the use of the mercury pump, usually exhibit lines caused by the presence of the vapor of this metal.In some cases this is no disadvantage, since they serve as convenient reference points in fixing the position of the othtlr lines or bands observed.As the mercury vapor is naturally an excellent, cond uctor of electricity, however, there is often reason to suspect tIl at its presence may affect the character of the discharge somewhat, and its removal becomes desirable.In some recent experiments hy the writer this end was obtained by placing in each tube a few pieces of clean gold foil loosely rolled into small pellets.As this metal is readily amalgamated it will, after a time, take up the mercul'Y vapor, clausing the disappearallce of its characteristic lines from the spectrum.A still better method is to wrap a small piece of the foil about the end of the electmde, 01' to attach to it a short gold wire.The gold will be volatilized and deposited upon the walls of the tube in a vel'y thin layer, thus exposing a much larger surface to the action of the mercury vapor, in the manner described below.In some of these expel'iments the tube nnder examination .wasso placed that the gold lay at the bottom of the upper portion, at the point w here the capillary part is attached.In this position it was exposed to the action of the more intense dischal'ge through the narrow part, and after a time it was found that a lustrous and coherent film was deposited upon the glass, the gold having evidently been volatilized by the electricity ann condensed upon the walls of the tube.In order to study more conveniently the conditions under which the best effects might be produced, a loose roll of the foil was placed in the middle of a tube about five millimeters in caliber, having a branch near one end for the purpose of withdl'awing the air, and with platinum electl'Odes inserted into the ends.This was exhausted until a diRchal'ge from an induction coil passed readily, when it was found that the gold was speedily deposited upon the tube as before, and by shaking the foil along, a considerable area was covered with it in a short time.It appeared, even under the microscope, as a perfectly continuous film, forming a brilliant mirror, and showing the characteristic green
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