text: 4 
  
  of the BIMSA3 appears to be negligible compared to the 
  1. The 
  reference term for concentrations less than 1 mol l− 
  perturbation can then be omitted to obtain a fully ana- 
  lytical theory, determined by the hard sphere diameters 
  and the pair fraction given by LPT; with the free energy 
  and the RDF given in terms of the BIMSA and MSA so- 
  lutions, as described above. While the procedure we have 
  followed uses two diﬀerent approximations for the refer- 
  ence and perturbation terms (MSA vs BIMSA), these are 
  known to be accurate for the systems under consideration 
  and do not appear to be inconsistent with each other. 