closed vessel. On removing the uranium no residual activity, however, was observed. They consider that this effect may be due to a very short-lived emanation emitted by uranium.
206. Effect of crystallization on the activity of uranium.
Meyer and Schweidler[1] recently observed that uranium nitrate,
after certain methods of treatment, showed remarkable variations
of its activity, measured by the β rays. The α ray activity, on the
other hand, was unaltered. Some uranium nitrate was dissolved
in water and then shaken up with ether, and the ether fraction
drawn off. The early experiments of Crookes showed that, by this
method, the uranium in the ether portion was photographically inactive.
This is simply explained by supposing that the uranium X is
insoluble in ether, and consequently remained behind in the water
fraction. The ether fraction gradually regained its β ray activity
at the normal rate to be expected if Ur X was produced by the
uranium at a constant rate, for it recovered half its final activity in
about 22 days. Some of the uranium in the water fraction was
crystallized and placed under an electroscope. The β ray activity
fell rapidly at first to half its value in the course of four days. The
activity then remained constant, and no further change was
observed over an interval of one month. Other experiments were
made with crystals of uranium nitrate, which had not been treated
with ether. The nitrate was dissolved in water and a layer of
crystals separated. The β ray activity of these crystals fell rapidly
at first, the rate varying somewhat in different experiments, but
reached a minimum value after about five days. The β ray
activity then rose again at a slow rate for several months.
The rapid drop of activity of the crystals seemed, at first sight, to indicate that crystallization was able in some way to alter the activity of uranium.
Dr Godlewski, working in the laboratory of the writer, repeated the work of Meyer and Schweidler, and obtained results of a similar character, but the initial drop of activity was found to vary both in rate and amount in different experiments. These results were at first very puzzling and difficult to explain, for the mother liquor, left behind after removal of the crystals, did not show the
- ↑ Meyer and Schweidler, Wien Ber. 113, July, 1904.
