  We report the charge doping of KCr$_3$As$_3$ via H intercalation. We show
that the previously reported ethanol bath deintercalation of K$_2$Cr$_3$As$_3$
to KCr$_3$As$_3$ has a secondary effect whereby H from the bath enters the
quasi-one-dimensional Cr$_6$As$_6$ chains. Furthermore, we find that - contrary
to previous interpretations - the difference between non-superconducting
as-grown KCr$_3$As$_3$ samples and superconducting hydrothermally annealed
samples is not a change in crystallinity but due to charge doping, with the
latter treatment increasing the H concentration in the CrAs tubes effectively
electron-doping the 133 compound. These results suggest a new stoichiometry
KH$_x$Cr$_3$As$_3$, that superconductivity arises from a suppressed magnetic
order via a tunable parameter and pave the way for the first charge-doped phase
diagram in these materials.
