🚀 go-pugleaf

Ray Rogoway (rrogowa@CELLO.GINA.CALSTATE.EDU) wrote:

> Thorium nitrate was used in a Project Physics experiment, entitled Half-Life.

Here is what E. Rutherford, then at Montreal (1900), wrote about thorium
compounds. It is just an interesting story to share with students on the
occasion of the approaching anniversary of the discovery of radioactivity
(1897). The book edited by A. Romer, and published in 1964 by Dover, "The
Discovery of Radioactivity and Transmutations" is an excelent source of
original articles. I am quoting from page 38.

"Thorium compounds under certain conditions possess the property of producing
temporary radioactivity in all solid substances in their neighbourhood. The
substance made radioactive behaves, with regards to its electric and
photographis actions, as if it was covered with a layer of radioactive
substance like uranium or thorium. Unlike radiations from thorium and uranium,
which are given out uniformly for long periods of time, the intensity of the
excited radiation is not constant, but gradually diminishes. The intensity
falls to half of its value about eleven hours after the removal of the
substance from the neighbourhood of thorium"

That is how the hypothesis of radiactive decay (one relatively stable
substance produces another, less stable substance) was first formulated.
I have the article in front of me. Figure 1 shows the experimental setup;
an electrometer (CAPACITOR C1) connected in series with the ionization
chamber (ANOTHER CAPACITOR, C2) and with a source of constant voltage.

The second paragraph begins with the following sentence. "Attention was
first drawn to this phenomenon of what may be termed excited radioactivity
by the apparent failure of good insulators, like ebonite and paraffin, to
coninue to isolate in the presence of thorium compounds."

Roy, I like Frost's poem you quote:

     "The words are lovely dark and deep but I have promises to keep ..."