Rays of positive electricity and their application to chemical analyses / [Sir J.J. Thomson].

  • Thomson, J. J. (Joseph John), 1856-1940.
Date:
1921
Catalogue details

Licence: In copyright

Credit: Rays of positive electricity and their application to chemical analyses / [Sir J.J. Thomson]. Source: Wellcome Collection.

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    between two points AB situated on the same vertical line will be twice the vertical deflection due to either magnetic field. As these arcs are much finer than the central spot, the distance AB can be measured with greater accuracy than either deflection separately. If, as is very often the case, we can recognize two parabolas as due to atoms, or molecules of known atomic weight, we can eliminate any uncertainty arising from the position of the zero without reversing the magnetic field. For if Tx, T2, T3 are the vertical displacements corresponding to particles with charge e and masses tnlf mz h Tc At = . rh and Ai = A / As T, 'm, in hence T< in. m* L + la sjmx + Ta =L{ -Tit V m2 s/m -L) s/mXJ Since T3 — Tx and T2 — Tx are independent of the position of the zero, any indeterminateness in that point will not affect the values of mz obtained by this equation. When the values of mv in2> mz are so close together that a horizontal line cuts within the limits of the plate the three parabolas corresponding to them, it is better to measure the horizontal rather than the vertical displacements. When we measure the displacements along a horizontal line, y is constant, so that from the equation B2 'm A we get, if xv x2, are the values of x where the horizontal line cuts the three parabolas, in2 in 3 •Xi or