  Let us consider some Coulomb systems of several infinitely massive centers of
charge Z and one-two electrons: $(Z,e)$, $(2Z,e)$, $(3Z,e)$, $(4Z,e)$,
$(2Z,e,e)$, $(3Z,e,e)$. It is shown that the physical, integer charges
$Z=1,2,...$ do not play a distinguished role in total energy and equilibrium
distance of a system giving no indication to a charge quantization.
  By definition, a critical charge $Z_{cr}$ for a given Coulomb system $(nZ,e)$
or $(nZ,e,e)$ is a charge which separates a domain of the existence of bound
states from a domain of unbound ones (continuum). For all above-mentioned
systems critical charges $Z_c$ as well as equilibrium geometrical
configurations are found. For all studied systems there was obtained an
indication to a square-root singularity at $Z=Z_{cr}$.
