Unequal-concentration second-order integration (source code)

= Unequal-concentration second-order integration
{title2=$\ln(hx_0/(xh_0))=k\Delta t$}

For a one-to-one <elementary reaction> with <concentrations> x and h, the difference $\Delta=h_0-x_0$ remains constant. Integration gives $\ln(hx_0/(xh_0))=k\Delta t$ when $\Delta\ne0$; the equal-initial-concentration limit is $1/x-1/x_0=kt$.