Fig. 42.
The complex character of the radium curves are more clearly brought out by a careful examination of a portion of the curve at distances between 2 and 5 cms. from the radium, using an ionization vessel of depth only 2 mms. The results are shown in [Fig. 42], where the curve is seen to consist approximately of four straight lines of different slopes represented by PQ, QR, RS, ST.
Such a result is to be expected, for it will be shown later that four distinct α ray products exist in radium when in radio-active equilibrium. Each of these products of radium emits an equal number of α particles per second, but the range of each is different. If a1 is the range of one stream, a2 of another, the ionization in the vessel AB, when two streams enter the vessel, should be
nb nb
---- (a1-h-b/2) + ----- (a2 – h – b/2),
ρ ρ
i.e.
nb
---- (a1 + a2 – 2h – b) .
ρ