Abstract: Purification of haloaldehydes in a process that consists essentially of a first stage of purification in which the haloaldehydes are brought into contact with an absorbent solid, basic in nature, in the presence of water or free alcohols, and of a second stage of purification in which the halo-aldehydes thus treated are brought into contact with a solid absorbent carrying sulphonic, phosphonic or carboxylic acid groups in the form of salts of alkali or alkaline earth metals.

Abstract: Process for the separation of trioxane from aqueous solutions containing it together with formaldehyde, which comprises subjecting the said solutions to evaporation at temperatures of 100.degree. C or lower, at pressures lower than atmospheric, and with residence times of less than 1 minute under the evaporation conditions, with vaporization of a quantity of from about 5 to about 15% by weight of the solution introduced, and recovering the trioxane from the products evaporated in this way.

Abstract: A process for purifying a polymerisable monomer selected from the group consisting of cyclic ethers, hydrocarbon olefins, vinyl compounds, aldehydes, lactams of the formula: ##EQU1## wherein x is an integer from 3 to 13 and lactones of the formula: ##EQU2## wherein n is an integer of from 1 to 4 and wherein R represents an hydrogen atom, an alkyl group or an aryl group; said process comprising contacting a liquid consisting of said monomer at a temperature of not greater than 130.degree. centigrade and at a pressure sufficient to keep said monomer in liquid form, with a solid absorbent consisting essentially of a porous reticulated macromolecular alkali metal or alkaline earth metal salt of a cationic exchange resin containing carboxylic, sulfonic or phosphoric acid groups, said cationic exchange resin having a specific surface area of at least one square meter per gram and a pore diameter of from 10.sup.1.3 to 10.sup.5 angstroms and recovering the purified monomer.