def get_rxn_params_dt(rxn, rev=False):
    """Write evaluation of the forward/reverse reaction rate constant

    Parameters
    ----------
    rxn : `ReacInfo`
        The reaction to consider
    rev : bool, optional
        If true, get the reverse constant rate constant derivative

    Returns
    -------
    jline : str
        String containing evaluation of forward/reverse reaction rate constant

    """
    jline = ''
    if rev:
        if (abs(rxn.rev_par[1]) > 1.0e-90
            and abs(rxn.rev_par[2]) > 1.0e-90):
            jline += ('{:.16e} + '.format(rxn.rev_par[1]) +
                      '({:.16e} / T)'.format(rxn.rev_par[2])
                      )
        elif abs(rxn.rev_par[1]) > 1.0e-90:
            jline += '{:.16e}'.format(rxn.rev_par[1])
        elif abs(rxn.rev_par[2]) > 1.0e-90:
            jline += '({:.16e} / T)'.format(rxn.rev_par[2])
    else:
        if (abs(rxn.b) > 1.0e-90) and (abs(rxn.E) > 1.0e-90):
            jline += '{:.16e} + ({:.16e} / T)'.format(rxn.b, rxn.E)
        elif abs(rxn.b) > 1.0e-90:
            jline += '{:.16e}'.format(rxn.b)
        elif abs(rxn.E) > 1.0e-90:
            jline += '({:.16e} / T)'.format(rxn.E)
    return jline