Abstract: Sol-gel process is a process of polymerization of chemical compounds (precursor) through hydrolysis and condensation in solution at low temperature. The pH precursor value can affect the solubility of the precursor and the soluble ion ratio of the ion. Fundamentally a sol solution having a pH at >7 would have a macroscopic morphology whereas at pH <7 has microscopic morphology. The purpose of this study was to determine the optimum conditions of the thin film produced from the sol-gel process to later be applied as a coating on the organo-silica membrane for saltwater desalination process. The method used in this research is sol-gel using two catalyst (base and organic acid), with ratio 1 : 38 : X : 5 : Y(molar ratio). X:Y is citric acid (C6H8O7):ammonia(NH3). Comparison molar ratio of citric acid : ammonia are 0.01 : (0.01; 0.0015; 0.001) and 0.001 : (0.01; 0.0015; 0.001) at 0OC. It will be characterized using FTIR test. The results of this study showed that the lower the molar catalyst ratio of citric acid, it be the higher the pH and the larger the pore size. In samples yielding a pH ranging from 5,32-8,56. At pH acid produces silanol (2.0) and siloxane (7.4) while at alkaline pH produces silanol (1.7) and and siloxane (6.2). So, the optimum sols as the thin films produced are pH 6.0 which has silanol (1.0) and siloxane (4.7). The optimum xerogel calcination is present at 175OC condensation temperature, it’s because of the remaining carbon bond content of silica carbon structure C=C-H (alkena) at peak 3750cm-1. Carbon bonds on the membrane can make the membrane stable. Keywords: ammonia, citrit acid, silica-carbon thin film, xerogel