def CellAbsorption(ElList, Volume):
    """Compute unit cell absorption

    :param dict ElList: dictionary of element contents including mu and
      number of atoms be cell
    :param float Volume: unit cell volume
    :returns: mu-total/Volume
    """
    muT = 0
    for El in ElList:
        muT += ElList[El]['mu'] * ElList[El]['FormulaNo']
    return muT / Volume
