  The absolute value of the electrical conductivity sigma of elemental metals
even at the room temperature range is not well theoretically understood. This
is particularly true in multivalent metals. This paper empirically found that
sigma=n_{atom}e^2tau0/mG with tau0=hbar/k_{B}T reproduces the observations
rather well for many metals as in Fig.1(b)-upper, if G is taken, by guessing to
be a summed number of electric bands counted from outer most orbitals. We find
by comparative study at the same time n_{atom}=n, namely Z=1 and m=m^* for
majority of metals for sigma. Thus the only quantity remained is tau. The
Bardeen's tau is found equal to tau0 if the deformation potential is equal to
Fermi energy, using the observationally ascertained fact that thermal acoustic
energy=the Fermi energy. Since electrons behave nearly as free electrons, the
wave function should show the minimum uncertainty relation of Delta p_{x}
Delta_{x}=hbar/2, which following the classical Fluctuation-Dissipation-Theorem
shows in fact tau0=hbar/k_{B}T.
