Page:Radio-activity.djvu/386

 A table of the transformation products of thorium is shown below, with some of their physical and chemical properties.

+-+-+-++-+ +-+-+-++-+ +-+-+-++-+
 * Product | Time to be half  |λ (sec)^{-1}|   Radiations   |   Physical and    |
 * |   transformed    |                   |                |chemical properties|
 * Thorium |                   |                   |  α rays  |Insoluble in       |
 * [v]   |                   |                   |                |  ammonia          |
 * Th. X   |   4 days          |  2·00 × 10^{-6}   |  α rays  |Soluble in ammonia |
 * [v]   |                   |                   |                |                   |
 * Emanation| 54 secs.         |  1·28 × 10^{-2}   |  α rays  |Inert gas,         |
 * [v]   |                   |                   |                |  condenses 120° C.|
 * Thorium A| 11 hours}        |  1·75 × 10^{-5}   |    no rays     |} Soluble in       |
 * |    |         }         |                   |                |} strong acids.    |
 * |    |         } Active  |                   |                |} Volatile at a    |
 * |    |         } deposit |                   |                |} white heat.      |
 * [v]   |         }         |                   |                |} B can be         |
 * Thorium B| 55 mins.}        |  2·1 × 10^{-4}    |α, β,|} separated from A |
 * |    |                   |                   |  γ rays  |} by electrolysis  |
 * |    |                   |                   |                |} and by difference|
 * [v]   |                   |                   |                |} of volatility.   |

211. Transformation products of Actinium. It has previously been pointed out (sections 17 and 18) that the actinium of Debierne and the emanium of Giesel contain the same radio-active constituent. Both give out a short-lived emanation which imparts activity to the surface of bodies. Recently, thanks to Dr Giesel of Braunschweig, preparations of "emanium" have been placed on the market, and most of the investigations that are described later have been made with this substance.

Actinium X. Actinium and thorium are very closely allied in radio-active properties. Both emit an emanation which is rapidly transformed, but the rate of change of the actinium emanation is still more rapid than that of thorium, the activity decreasing to half value in 3·7 seconds. Miss Brooks has analysed the active deposit from the emanation of actinium, and has shown that two successive changes occur in it, very similar in character to those observed in the active deposit of thorium. It thus seemed