AbstractA comparative study of the hydrolysis of the symmetrical orthosilicates, tetra‐ethyl,‐ tetra‐butyl, tetra‐hexyl, tetra‐2,6‐dimethyl‐heptyl‐4‐silicate, and of the unsymmetrical orthosilicates, diethyl‐dihexyl, diethyl‐di‐2‐methylpentyl‐4, diethyl‐diheptyl‐2, diethyl‐di‐2,6‐dimethyl‐heptyl‐4‐silicate, has been undertaken. A mechanism of the hydrolysis and of the polycondensation reaction of the silicols formed is proposed. Methods of preparation of some polyalkoxysiloxanes are described and the boiling points, melting points and densities determined. The higher polymers obtained by hydrolysis of alkoxy silicates are always highly cross‐linked siloxane networks. Attempts to obtain linear polyalkoxysiloxanes of high molecular weights by the hydrolysis of unsym