A self-sustaining controlled acid–base reaction between oxalotitanic acid [H 2TiO(C 2O 4) 2] (HTO) and barium hydroxide [Ba(OH) 2·8H 2O] at room temperature is utilized for the quantitative precipitation of barium titanyl oxalate (BTO). For this purpose, an intermediate soluble oxalotitanic acid precursor is generated by reacting 0.1 M solution of titanium tetrabutoxide in isopropanol (IPA) with 0.2 M solution of oxalic acid in IPA. Equimolar suspended Ba(OH) 2 particles in IPA were mixed with the above-mentioned oxalotitanic acid solution. The self-sustaining acid–base reaction between Ba(OH) 2 and H 2TiO(C 2O 4) 2 was initiated only when necessary amount of water was added. This shift from non-aqueous to semi-aqueous condition allows a required solubility of Ba(OH) 2, which makes Ba 2+ ions available for the exchange reaction. The solubility of Ba(OH) 2 and its dissociation governs the kinetics of the reaction leading to the precipitation of BTO with yield ≥99%. The controlled pyrolysis of BTO at 750 °C/4 h in air-produced agglomerated cubic BaTiO 3 powders having spherical particles with size ≈100 nm. These powders are sintered in the form of pellets at 1300 °C/4 h to obtain compacts with density ≈95%. These compacts showed dielectric constant ε RT=1680 (tan δ≤2%), ε max≈7780 at T C=121 °C.