def FF_critical_pressure_ratio_l(Psat, Pc):
    """Calculates FF, the liquid critical pressure ratio factor,
    for use in IEC 60534 liquid valve sizing calculations.

    .. math::
        F_F = 0.96 - 0.28\\sqrt{\\frac{P_{sat}}{P_c}}

    Parameters
    ----------
    Psat : float
        Saturation pressure of the liquid at inlet temperature [Pa]
    Pc : float
        Critical pressure of the liquid [Pa]

    Returns
    -------
    FF : float
        Liquid critical pressure ratio factor [-]

    Examples
    --------
    From [1]_, matching example.

    >>> FF_critical_pressure_ratio_l(70100.0, 22120000.0)
    0.9442375225233299

    References
    ----------
    .. [1] IEC 60534-2-1 / ISA-75.01.01-2007
    """
    return 0.96 - 0.28 * (Psat / Pc) ** 0.5
