IR spectra of small B...HCl (B = HCl, N₂, Xe, CO) complexes have been studied in solid phase at equilibrium conditions by using the technique of crystal growth from a liquid Kr solution. Triplet to doublet structure evolution of the v(HCl) fundamental band has been revealed at liquid to crystal state transition of the noble (Xe, Kr) gas solutions. Residual rotational structure observed at wings of the v(HCl) band and spectral moments analysis suggest that noncomplexed HCl molecules continue to rotate in solid solutions studied. Self-association of HCl molecules has been found in solid Kr, while this process was strongly suppressed in solid Xe. Spectral parameters of the v(c) fundamental bands and enthalpy of formation ΔH were estimated for B...HCl complexes in solid Kr. Comparative analysis of the v(c)(CO) and v(c)(HCl) bands shows that the v(c)(HCl) band is perturbed due to intermolecular H-bonding and the OC...HCl complex does not rotate in solid Kr. Relative changes of the integral intensity A of the fundamental v(c)(HCl) and v(c)(CO) bands due complex formation have been derived from the temperature dependence of the A value.