  We present the Bjorken integral extracted from Jefferson Lab experiment EG1b
for $0.05<Q^{2}<2.92$ GeV$^2$. The integral is fit to extract the twist-4
element $f_{2}^{p-n}$ which appears to be relatively large and negative.
Systematic studies of this higher twist analysis establish its legitimacy at
$Q^{2}$ around 1 GeV$^{2}$. We also performed an isospin decomposition of the
generalized forward spin polarizability $\gamma_{0}$. Although its isovector
part provides a reliable test of the calculation techniques of Chiral
Perturbation Theory, our data disagree with the calculations.
