  Two theories for associating fluids recently used to study clustering in
models for self-assembling patchy particles, Wertheim's and
Bjerrum-Tani-Henderson theories, are carefully compared. We show that, for a
fluid allowing only for dimerization, Wertheim theory is equivalent to the
Bjerrum-Tani-Henderson theory neglecting intercluster correlations.
Nonetheless, while the former theory is able to account for percolation and
condensation, the latter is not. For the Bjerrum-Tani-Henderson theory we also
rigorously prove the uniqueness of the solution for the cluster's
concentrations and the reduction of the system of equations to a single one for
a single unknown. We carry out Monte Carlo simulations of two simple models of
dimerizing fluids and compare quantitatively the predictions of the two
theories with the simulation data.
