Abstract: A mixture of short-chain polysulfide silanes having the formula: (RO).sub.3 SiC.sub.3 H.sub.6 S.sub.n C.sub.3 H.sub.6 Si(OR).sub.3 wherein R is methyl or ethyl and n is a positive number having a distribution in the average range of 2.1.ltoreq.n.ltoreq.2.9, is prepared by reacting one mole of an anhydrous sulfide of the formula: M.sub.2 S or NS wherein M is an alkali metal or ammonium and N is an alkaline earth metal or zinc, with (n-1) mole of sulfur in an inert gas atmosphere and in a polar solvent, thereby forming polysulfide compounds, and reacting the polysulfide compounds with a halogenopropyltrialkoxysilane of the formula: (RO).sub.3 SiC.sub.3 H.sub.6 X wherein R is as defined above and X is a halogen atom. The method is simple to produce polysulfide silanes in high yields.

Abstract: A water soluble water absorption preventing agent mainly comprising an organic silicon compound and/or its partial hydrolytic condensate, represented by the following general formula: ##STR1## wherein R.sup.1 denotes an alkyl group with 1-20 carbon atoms and with a linear chain or branched chain for which a halogen can substitute for part or all of the hydrogen atoms, R.sup.2 denotes a hydrogen atom or an alkyl group with 1-10 carbon atoms and with a linear chain or branched chain, R.sup.3 denotes a hydrogen atom or an alkyl group with 1-8 carbon atoms and with a linear chain or branched chain, m denotes an integer 1-2 and n denotes an integer 1-3 where m+n=3 or 4, p denotes an integer 1-50, and q denotes an integer 0-25.