Abstract:According to the principles of simultaneous equilibrium and electronic charge neutrality, the thermodynamics of Sn(IV)-NH⁴⁺-Cl^--H₂O system under normal condition was calculated. Relation between all sorts of complex of Sn⁴⁺and pH was plotted. Based on thermodynamics analysis and calculation, some experiments were done to validate the relation between the total concentration of tin ion and pH in this system. The results suggest that the total concentration of
ammonium and pH are the most important factors which determine whether (NH₄)₂SnCl₆ or Sn(OH)₄exists in this system. Results further suggest when contnet of HCl is more than 6 mol/L, Sn⁴⁺in this system will be also precipitated in the form of (NH₄)₂SnCl₆. These results lay the solid theory foundation to prepare pure (NH₄)₂SnCl₆, a promising substitution for SnCl₄·5H₂O to prepare antimony doped tin oxide(ATO) and indium tin oxide(ITO), from the tinny material.

Key words: thermodynamic calculation; Sn(IV)-NH⁴⁺-Cl^--H₂O; (NH₄)₂SnCl₆