The complete or partial removal of polar and/or readily polarisable constituents from admixture with constituents of comparable or lesser polarity and of differing molecular dimensions is effected by contacting the mixture with dehydrated crystalline zeolites, natural or synthetic, the constituents removed having a polarity comparable with or greater than the components remaining and molecular dimensions such that in the pure state they are occluded by the dehydrated crystals at rapid or finite rates, and the other constituents having a polarity comparable with or less than those removed and molecular dimensions such that in the pure state they either are not occluded by the crystals or are occluded by the crystals considerably more slowly. The separation may be either complete or partial, in the gas and/or vapour and/or liquid phases by either flow or static methods. The following separations are specifically claimed: hydrogen chloride from paraffins, cycloparaffins, aromatic hydrocarbons, alkyl chlorides, alkylene chlorides and aryl chlorides; chlorine and/or methyl chloride from paraffins containing at least three carbon atoms in the molecule cycloparaffins, aromatic hydrocarbons, alkyl chlorides other than methyl chloride, alkylene chlorides and aryl chlorides; dichlor methane and/or ethyl chloride from branched chain paraffins, straight chain paraffins having more than four carbon atoms in the molecule, cycloparaffins and aromatic hydrocarbons, alkyl chlorides derived from these hydrocarbons, chlorides derived by substitution from cycloparaffins, aryl chlorides, secondary chlorides derived from straight chain paraffins containing less than five carbon atoms in the molecule, polychlorinated hydrocarbons containing from two to four carbon atoms in the molecule, chloroform and carbon tetrachloride; hydrogen bromide, bromine and methyl bromide from paraffins containing at least three carbon atoms in the molecule, cycloparaffins, aromatic hydrocarbons, bromides derived from these hydrocarbons, tribrom - methane, tetrabrom - methane and polybrom-ethanes; ethyl bromide and/or methylene dibromide from branched chain paraffins, cycloparaffins, straight chain paraffins having more than six carbon atoms in the molecule; bromides derived from these hydrocarbons, secondary bromides derived from straight chain hydrocarbons having less than seven carbon atoms in the molecule, tribrom-methane, tetrabrom-methane and polybrominated derivatives of straight chain hydrocarbons having at least two carbon atoms in the molecule; hydrogen iodide, iodine and methyl iodide from branched chain paraffins, cycloparaffins, straight chain paraffins having more than six carbon atoms in the molecule, aromatic hydrocarbons, alkyl iodides having more than one carbon atom in the molecule and aryl iodides; ammonia from paraffins, cycloparaffins, aromatic hydrocarbons and amines; methylamine from paraffins containing more than two carbon atoms in the molecule, cycloparaffins, aromatic hydrocarbons and amines other than methylamine; ethylamine from branched chain paraffins, cycloparaffins, aromatic hydrocarbons, straight chain paraffins having at least six carbon atoms in the molecule, amines derived from these hydrocarbons, amines of straight chain paraffins containing less than 5 carbon atoms in the molecule having an amino group attached to a secondary carbon atom and secondary and tertiary amines derived from straight chain hydrocarbons containing less than five carbon atoms in the molecule, except dimethylamine; methyl alcohol from paraffins, cycloparaffins, aromatic hydrocarbons, phenols, alcohols other than methyl alcohol, ketones, esters, ethers and heterocyclic compounds; ethyl alcohol from paraffins containing at least three carbon atoms in the molecule, cycloparaffins, aromatic hydrocarbons, phenols and alcohols derived from paraffins containing at least three carbon atoms in the molecule, cycloparaffins and aromatic hydrocarbons, ketones, ethers (except dimethyl ether) esters and heterocyclic compounds; one or more of the compounds carbon dioxide, formaldehyde and methyl alcohol from paraffins containing at least three carbon atoms in the molecule, cycloparaffins, aromatic hydrocarbons, phenols and alcohols derived from these hydrocarbons, ketones, esters, ethers and heterocyclic compounds; water from aliphatic hydrocarbons, cycloparaffins, aromatic hydrocarbons, substitution derivatives of these hydrocarbons, heterocyclic compounds, ketones, ethers, thioethers, esters, secondary and tertiary amines; water from paraffins containing at least three carbon atoms in the molecule, cycloparaffins, aromatic hydrocarbons, substitution derivatives of these hydrocarbons, heterocyclic compounds, ketones, ethers, thio-esters, esters, secondary and tertiary amines, dibrom-methane, di-iodo-methane, methyl iodide, ethyl iodide, tri - halo - methanes, tetra - halo - methanes and poly-halo-ethanes; one or more of the compounds hydrogen sulphide, carbon disulphide, carbon oxysulphide and methyl mercaptan from paraffins containing at least three carbon atoms in the molecule, cycloparaffins, aromatic hydrocarbons, mercaptans derived from these hydrocarbons, alkyl and aryl sulphides; ethyl mercaptan from branched chain paraffins, cycloparaffins, aromatic hydrocarbons, straight chain paraffins having more than six carbon atoms in the molecule, mercaptans derived from these hydrocarbons, mercaptans derived from straight chain paraffins having less than seven carbon atoms in the molecule and having the mercaptan group attached to a secondary carbon atom, alkyl and aryl sulphides (except dimethyl sulphide); one or more of the compounds sulphur dioxide, nitric oxide, nitrogen dioxide and nitrogen trioxide from paraffins containing at least three carbon atoms in the molecule, cycloparaffins, aromatic hydrocarbons and nitro compounds derived from such hydrocarbons; hydrocyanic acid and/or aceto nitrile from paraffins containing at least three carbon atoms in the molecule, cycloparaffins, aromatic hydrocarbons, nitriles derived from these hydrocarbons and propionitrile; propionitrile from branched chain paraffins and cycloparaffins, straight chain paraffins having more than six carbon atoms in the molecule, nitriles derived from these hydrocarbons and those from straight chain hydrocarbons having less than seven carbon atoms in the molecule and having the nitrile group attached to a secondary carbon atom. In examples: (1) a mixture of CH3CN, CS2, CH3OH and C6H6 is filtered through de hydrated chabazite to obtain pure C6H6; (2) a mixture of C2H5OH and (CH3)3COH contacts dehydrated chabazite leaving a residue of (CH3)3C(OH); (3) a solution of bromine in carbon tetrachloride is contacted with dehydrated chabazite to remove the bromine; (4) a sample of crude ether containing water and ethyl alcohol is contacted with dehydrated chabazite leaving ether virtually free of water and ethyl alcohol; (5) a mixture of H2O and C2H5OH is contacted with dehydrated mordenite to obtain water-free alcohol; (6) a mixture of CH3OH and C2H5OH is contacted with mordenite leaving a liquid freed of CH3OH; (7) a mixture of CH3OH and aqueous ammonia is contacted through a quiescent layer of air via the vapour phase, with dehydrated barium base exchange mordenite to obtain CH3OH; (8) a mixture of dry HCl and C2H6 is contacted with dehydrated calcium base-exchange mordenite to remove the HCl. Many other examples are also disclosed including the drying of organic liquids, e.g. ethers, esters, or ketones; dehydration of aqueous alcohols; purification of acetone from methyl alcohol; purification of crude ether from ethyl alcohol and/or water; removal of CS2, CH3SH and C2H5SH and/or H2S from toluene or benzene; resolution of azeotropic mixtures such as are formed between methyl alcohol and pyridine or acetonitrile or between simple n-primary amines, alcohols or nitriles and hydrocarbons; separation of products of chlorination or bromination of methane; recovery of halogens and halogen hydracids from dry organic mixtures, e.g. during halogenation; separations of simple primary amines and/or ammonia from admixture with secondary and/or tertiary amines; removal of ethyl and methyl alcohols from admixture with any tertiary and/or secondary alcohols. All occluded solutes may be removed by either cold water, hot water or super-heated steam. Specifications 548,905, 574,911 and 600,465 are referred to.