SKDSDX    SKDSDX    SKDSDX    SKDSDX    SKDSDX    SKDSDX    SKDSDX    
          **********************************************
                    **************************
                              ******

SUBROUTINE SKDSDX (P, T, X, ACT, SDEN, ISKWRK, RSKWRK, DSDX, KDIM,
                   SDOT, SITDOT)
Returns the partial derivative of the production rates of the
species with respect to the activity for each species.
It also returns the matching production rates.

INPUT
P         - Real scalar, pressure.
               cgs units, dynes/cm**2
T(*)      - Real array, temperature(s); dimension is determined by
            the application program to be the total number of
            species temperatures, nominally 1.
               cgs units, K
X(*)      - Real array, mole fraction (or its equivalent) of the
            species;
            dimension at least KKTOT, the total species count.
            The first KKGAS X are mole fractions,
            the next KKSURF X are site fractions
               (species density normalized by the site density;
                surface concentration in moles/cm**2 is
                X(K)*SITE_DENSITY / # sites per species),
            the next KKBULK X are bulk species mole fractions.
ACT(*)    - Real array, activities of the species;
            dimension at least KKTOT, the total species count.
            The first KKGAS activities are mole fractions,
            the next KKSURF activities are site fractions
               (species density normalized by the site density;
                surface concentration in moles/cm**2 is
                ACT(K)*SITE_DENSITY / # sites per species), and
            the next KKBULK activities for bulk phase species
            should be from 0 to 1, and should sum to 1 for each
            phase.
SDEN(*)   - Real array, site densities for the site types;
            dimension at least NPHASE, the total phase count,
            but the subroutine only uses site phase entries,
            NFSURF <= N <= NLSURF.
               cgs units, moles/cm**2.
ISKWRK(*) - Integer workspace array; dimension at least LENISK.
RSKWRK(*) - Real    workspace array; dimension at least LENRSK.
KDIM      - Integer scalar, actual first dimension of DSDX.

OUTPUT
DSDX(*,*) - Real matrix, partial derivatives of the production rates
            of the species with respect to the activity of species
            KSPEC;
            dimension at least KKTOT, the total species count, for
            both the first and second dimensions.
               cgs units, moles/(cm**2*sec) / (units of KSPEC)
SDOT(*)   - Real array, production rates of the species;
            dimension at least KKTOT, the total species count.
               cgs units, moles/(cm**2*sec)
            SDOT(K) is
            for 1,KKGAS, the production rate of gas-phase species,
            for KKGAS+1,KKGAS+KKSUR, the production rate of surface
            species,
            for KKGAS+KKSUR+1,KKTOT, the production rate of bulk
            species.
SITDOT(*) - Real array, production rates of the surface phases;
            dimension at least NPHASE, the total phase count, but
            subroutine only calculates entries for site phases.
               cgs units, moles/(cm**2*sec)