  The decay of the Standard Model Higgs boson in the intermediate-mass range
into gluons is considered where special emphasis is put on the influence of the
leading electroweak corrections proportional to G_F m_t^2. An effective
Lagrangian approach is used where the top quark is integrated out. The
evaluation of the coefficient function is performed using two different
methods. The first one is concerned with the direct evaluation of the vertex
diagrams and the second method is based on a low-energy theorem. In a first
step the tools needed for the computation are provided namely the
renormalization constants of the QCD Lagrangian are computed up to O(\alpha_s^2
G_F m_t^2). Also the decoupling constants for the strong coupling constant
\alpha_s and the light quark masses relating the quantities of the full theory
to the corresponding quantities of the effective one are evaluated up to order
\alpha_s^2 G_F m_t^2.
