Calcium carbonate precipitation was investigated in the gas-slurry system in the reaction of calcium hydroxide and carbon dioxide. The precipitation process was occurred in the presence of ethylene glycol (EG). The used organic additive changed the viscosity of reactive mixture, the solubility of carbon dioxide and the solubility of calcium carbonate which influence CaCO3 precipitation conditions. The course of reaction was monitored by conductivity probe. The increase concentration of ethylene glycol in the reactive mixture caused higher CO2 usage to achieve the end point of reaction. Calcium carbonate was precipitated as calcite and produced CaCO3 particles formed agglomerates in all experiments. The size of obtained CaCO3 particles decreased when the EG concentration increased from 0% to 15% (by vol.). The further increase of EG concentration in solution up to 20% resulted in an increase of the size of CaCO3 particles. (C) 2011 Elsevier B.V. All rights reserved.