  In primordial gas, molecular hydrogen forms primarily through associative
detachment of H- and H, thereby destroying the H-. The H- anion can also be
destroyed by a number of other reactions, most notably by mutual neutralization
with protons. However, neither the associative detachment nor the mutual
neutralization rate coefficients are well determined: both may be uncertain by
as much as an order of magnitude. This introduces a corresponding uncertainty
into the H2 formation rate, which may have cosmological implications. Here, we
examine the effect that these uncertainties have on the formation of H2 and the
cooling of protogalactic gas in a variety of situations. We show that the
effect is particularly large for protogalaxies forming in previously ionized
regions, affecting our predictions of whether or not a given protogalaxy can
cool and condense within a Hubble time, and altering the strength of the
ultraviolet background that is required to prevent collapse.
