Abstract: Oligoglycerol mixtures having a high diglycerol content are prepared by a process in which glycerol is condensed in the presence of zeolites corresponding to formula (I)M.sub.2/z O * Al.sub.2 O.sub.3 * x SIO.sub.2 * y H.sub.2 O (I)in which M is an alkali metal or alkaline earth metal having a valency of z, x is a number of 1.8 to 12 and y is a number of 0 to 8. The water of condensation which is formed during the reaction, is continuously removed from the reaction mixture and the reaction is terminated when the quantity of water theoretically necessary for the formation of diglycerol has been separated.

Abstract: Method for producing alkali metal silicates from crystalline siliceous material and aqueous alkali metal hydroxide solution at high temperature and normal pressure, characterized in that cristobalite and/or tempered quartz sand are used as the siliceous material, and this material is reacted with aqueous, 20 to 50 wt. % sodium or potassium hydroxide solution at temperatures of 100.degree. to 150.degree. C. and normal pressure, the molar ratio of SiO.sub.2 to Na.sub.2 O or K.sub.2 O in the reaction mixture being between 2:1 and 1:7.