Solving ODEs in quasi steady state

Solving ordinary differential equations (ODEs) with solutions in a quasi steady state has been studied by computational chemists, applied mathematicians, and numerical analysts. This paper first discusses what stiffness is for model problems arising in chemical kinetics. Chemists and applied mathematicians have made use of quasi-steady-state approximations (singular perturbation theory) to alter the problem so as to avoid stiffness. The approach is described and some difficulties are noted. Numerical analysts have developed methods to solve general stiff ODEs. How they relate to the problem at hand is described and some difficulties are pointed out. Finally, ideas from both approaches are combined. The new combination deals effectively with stiffness when the quasi steady state hypothesis is valid