VERFAHREN ZUM HERSTELLEN VON HYDROTHERMALEN WASSERGLAESERN.

摘要

In hydrothermal prodn. of Na silicate solns. (I) with a SiO2: Na2O wt. ratio of 1.95-1.6:1 by reacting sand, NaOH and water, the novel features are that sand is used in less than the stoichiometric amt. w.r.t. the 2:1 wt. ratio and the reaction temp. is 190-240 deg.C. Pref. the SiO2:Na2O ratio=1.9+/-0.05:1, the reaction temp. is 200-230 deg.C, the pressure that of satd. steam at this temp. and the NaOH concn. 36.5-48.5% and reaction is continued to at least 99.7% conversion w.r.t. sand. Pref. sand and aq. NaOH soln. are mixed in a SiO2:Na2O ratio of 8:4.45 +/-0.3, more water is added if necessary, and the mixt., with a SiO2:Na2O molar ratio=1.927-1.68:1, pref. 1.8:1 and a max. molar concn. of SiO2:H2O=1:3 and Na2O:H2O=1:6 is heated in an autoclave for 35+/-5 min. at 215 +/- 5 deg.C. The soln. obtd. is purified by sedimentation esp. in an inclined clarifier.