File:Transactions and proceedings and report of the Philosophical Society of Adelaide, South Australia (1911) (14577703208).jpg

Identifier: transactionsproc3536phil (find matches)
Title: Transactions and proceedings and report of the Philosophical Society of Adelaide, South Australia
Year: 1878 (1870s)
Authors: Philosophical Society of Adelaide, South Australia
Subjects: Philosophical Society of Adelaide, South Australia Science
Publisher: Adelaide : The Society
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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rough a Faraday tube (fig. 5a), which serve respectively tomeasure the total ionization of a given sign or mobility of theions and the total charge. The outline, P, in fig. 5a representsa plug of cotton wool. The height of the vessel, ^4, and thematerial of the target can be varied at will. The first experiments with this apparatus were directedto a confirmation of the law that the ionization is propor-tional to the energy of impact, i.e., in this case, to the heightof fall. The accuracy with which this law holds for the impactof a stream of leaden shot on a brass target is shown by fig. 6. The mobility of the ions was determined by Zelenysmethod (J. J. Thomson, Conduction of Electricity throughGases, 2nd Ed., p. 58). The saturation curves for the positiveand negative ions respectively are shown in fig. 7, a and b.The values of the mobilities when the abscissae of the pointsX and Y were used in calculating were 1*6x10-^ cm./sec.per volt/cm. for both positive and negative ions, but the
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1520^-5 \ i ——^ —^ —B— r ^ . 1 5 X e> » < 1 < ^ c 50 100 150 ZOO 250 300 350 400 10 nature of tlie curves shows that they are produced by a mix-ture of ions of varying mobility, the mean mobilities, how-ever, being the same for positive and negative ions. No point of inflexion could be found in the mobilitycurves, even when the field reached a value of 400 volts/cm. The shot used in these experiments and in the precedingweighed 0392 gm. per shot. When glass beads (diameter036 in.) were substituted for the shot and allowed to fallthrough a glass tube on a glass target the saturation curvesshown in fig. 8 were obtained. The character of these curvesshows that the variety of ions is still greater than in thecase of those produced by lead shot. Calculating for thepoints r and Q as the elbows of the curves the mobilities arefound to be 1*0 x 10 ^ for both positive and negative ions. The sign of the total charge on the air drawn over thetarget was determined by drawing i

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