VERFAHREN ZUR HYDROTHERMALEN HERSTELLUNG VON NATRIUMSILIKATLOESUNGEN

1. A process for the hydrothermal production of sodium silicate solutions having a ratio by weight of SiO2 to Na2 O of from 1 to 2.8:1 by reacting sand with aqueous sodium hydroxide solution under pressure and at elevated temperatures, followed by filtration, characterised in that a. aqueous sodium hydroxide solution having a concentration of from 10 to 50% by weight is reacted with b. an excess of sand of up to 300%, based on the molar ratios of SiO2 to Na2 O in the mixture c. at temperatures in the range from 150 to 250 degrees C and under the saturated steam pressures corresponding to these temperatures and d. the unreated excess of sand is used wholly or in part as filter medium for the sodium silicate solution formed.