  The temperature dependence of the uniform susceptibility, chi, of diluted
two-dimensional Ising antiferromagnets Rb2Co1-xMgxF4,0<=x<=0.4, is investigated
in the limit of vanishing external field. Novel data for x = 0.15 are compared
with those obtained for x = 0 and 0.4 by Breed et al. (1969) and Ikeda (1983),
respectively. Whereas in the pure case, x = 0, Fishers (1962) "energetic
contribution" dominates, Aharony et al.s (1979,1986) "random contribution"
becomes increasingly important with increasing x. Taking into account both
terms not only with respect to the global ordering temperature, TN(x), but also
in relation to the "local" phase transition temperatures TN throughout the
Griffiths regime,TN(x)<=TN<=TN(0), a satisfactory quantitative description of
chi vs. T is deduced for any x above the percolation threshold.
