A non-aqueous process for deacidifying and preserving cellulosic materials by means of a solution of an alkali or alkaline earth alkoxide, or mixtures thereof, in an organic solvent therefor. Also disclosed are nonaqueous deacidification processes employing other alkali and alkaline earth compounds, and processes which employ a liquefied gas and /or halogenated hydrocarbon solvent. Also disclosed are processes for deacidifying and preserving cellulosic aggregates such as whole books, and cellulosic plastics. -- AATA