The experiments of the author have been principally directed to the
alterations in shape and color produced in a flame when under the
influence of positive or negative electricity. The flames were arranged
so as to form one electrode of a frictional machine. When charged with
positive electricity the flame became more blue, narrower, and pointed
at the top, while little or nothing of the result was observed in
negative flames.
A peculiar result is that the end of a negative flame returns to its own
conductor, and that, according to the intensity of the electricity, and
also depending on the width of the burner, this turning back of the
flame is either intermittent or constant. Most noticeable are these
results:
When the flame rises from a circular burner, or when burning round a
metallic cylinder, in the latter case it returns to the metallic surface
according to the intensity of electricity in an arc or angle, while the
point of the flame divides into two branches, which separately perform
more or less equal movements. If a body connected to the earth by a
conducting wire is held opposite the flame at some distance, the flame
will in all cases bend toward it; as the body is brought closer,
the flame, if negative, will be repulsed, and, if positive, will be
attracted, at least the upper luminous part of the flame, while the
lower dark body of flame is also repulsed.
This phenomenon explains why a positive flame will burn through wire
gauze, while a negative flame remains below the gauze. The positive
flame becoming pointed explains the fact that this will drive a small
fan wheel, while a negative flame will only just move it.
All these results are most prominently obtained with a pure gas flame, a
stearine, wax, or tallow candle, very indifferently with a spirit flame,
and least from a Bunsen flame rich in oxygen. They may not only be
obtained with flames electrified direct, but also when placed under the
influence of a long "Holtz" machine.
A flame placed between two small disks on the machine bends toward the
negative pole, becomes widened, and, at a certain point of electric
intensity, commences to vibrate and oscillate, exhibiting a peculiar
stratification. Since these phenomena are also least observed in flames
rich in oxygen, it appears to be a general law that carbon and hydrogen
are more strongly attracted by the negative pole, while oxygen is
more attracted by the positive pole, probably like in all polar
differentially attractions, in consequence of a peculiar unipolar
conductivity of the substances.
The return motion of the flame the author explains thus: The point
of the flame loses more electricity by influence than it receives by
conductivity. A paper strip fixed at one end to a large ball shows
similar movements when its free end is pointed and made conductive.
Why principally the negative flame returns may be explained in two
ways--either the point of the flame loses much by radiation, or the base
of the flame is a bad conductor. The former explanation would agree with
the experiments made by Wiedemann and Ruhlmann, the latter with Erdman's
theory of unipolar conductivity of flames. This theory is still further
supported by the resistance on the negative electrodes noticed by
Hittorf, which almost explains Erdman's experiments, because if negative
electricity enters a flame with greater difficulty, then positive
electricity must leave a flame with difficulty.--_W. Holtz, in
Wiedemanris Beiblätter to Poggendorfs Annalen._
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