An interally consistent analysis of the available data on the conditions of the equilibrium of phases and thermodynamic properties of Si-B alloys based on silicon is performed. Phase equilibria in the Si-B-Ti system in the temperature and concentration regions of the existence of solid solution based on silicon are calculated using the obtained data. Conditions for the precipitation of titanium diboride from Si-B-Ti solid solution at 1523 K are found.Keywords: phase equilibria, solid solution of boron in silicon, thermodynamic properties, impurities in silicon.