  Any one measurement with polarized light makes it possible to fix the Mueller
matrices of the Lorentz type with up to four arbitrary numeric parameters (x,
u; z, w). These parameters are subject to the quadratic condition. It is
demonstrated that the quadratic form can be diagonalized; in the case of
partially polarized light four diagonal coefficients turn out to benon-zero and
positive; in the case of completely polarized light two diagonal coefficients
equal to zero.
