The Robertson biochemical reactions in DAE form

\[\frac{dy₁}{dt} = -k₁y₁+k₃y₂y₃\]

\[\frac{dy₂}{dt} = k₁y₁-k₂y₂^2-k₃y₂y₃\]

\[1 = y₁ + y₂ + y₃\]

where $k₁=0.04$, $k₂=3\times10^7$, $k₃=10^4$. For details, see: Hairer Norsett Wanner Solving Ordinary Differential Equations I - Nonstiff Problems Page 129 Usually solved on $[0,1e11]$