Downy Precipitate appeared in several aqueous solutions under ambient condition for some time.These solutions were orgsnic acids contained in glass vessels and experimental aqueous samples gotten with silicate rock gtains dissolved in organic acid solution. The main compeition of the Precipitate was known as cement of silica after analysis. The research results show that the stability of silica in the liquid increases with the increase of acidity of the liquid

and some low-molecular-weight organic acids which could form stable ring complexes with silica could stop the cementation of silica in liquid.