The degree of separation achieved by a single stage is known as the stage separation factor, or amply the separation factor a. This is defined as the weight, mole, or atom ratio in the heads stream divided by the corresponding ratio in the tails. For a two-component mixture,

_ t) у/(1-у) a~ t x/(l-x)

The separation factor defined in this way is useful because in many isotope separation processes, it is independent of composition. The ratio y/x, on the other hand, may vary strongly with composition.

Other useful measures of the degree of separation effected by a stage are the heads separation factor /3, defined by

n y/O-y)

І x/(i-*)

and the tails separation factor y, defined by

f x/(l-i) 7 І */(!-*)

The composition differences measured by a, /3, and у are indicated in Fig. 12.9 by the curved lines. From the definitions of a, (3, and y, it follows that

_ flz = ax
y~ Pz+l-z~ax+l-x

ax________ У

ax+ (3(1 — x)~y + /3(1 — y)

У _ i
y + a(l — y) z+y(l—z)

A relation between /3, a, and в may be obtained from (12.12), (12.15), and (12.16):

(a-1X1-0)

1 +0(a-lXl -У)