The invention comprises aluminium organic complexes of the Werner type which comprise negative ions which are anions of strong inorganic acids and positive complex ions in which nuclear aluminium atoms covalently linked to oxygen atoms in hydroxyl groups and/or to oxygen atoms linked also to other aluminium atoms, the numerical ratio of the oxygen atoms to aluminium atoms being greater than 1 : 1 but not exceeding 2,5 : 1, are co-ordinated with acyloxy groups of monocarboxylic acids of solubility in water at 20 DEG C. less than 1% by wt., the complexes being capable of forming with water a liquid composition in which individual particles of the complexes of molecular or colloidol size are dispersed and from which the particles do not settle on standing, and being obtainable by reacting the mono carboxylic acid in a liquid organic medium with a basic ionisable salt of aluminium in which the aluminium is bound partly to hydroxy groups and optionally also to oxygen-aluminium linkages and for the rest to radicals of strong inorganic acids, the basic ionisable salt having a basicity greater than 33 1/3 % but not exceeding 83 1/3 % (the salt AlX2OH has a basicity of 33 1/3 %). Reaction is suitably effected at from room temperature up to 100 DEG C with an alcohol or chlorinated hydrocarbon as organic medium. Water may be present in amount such that the total number of water molecules, hydroxyl ions, strong acid anions and carboxylic acid ions combined is less than 6 per aluminium atom. The strong inorganic ions may be those of hydrochloric, hydrobromic, hydroiodic, nitric or chloric acid. Numerous suitable monobasic carboxylic acids are listed including saturated and unsaturated aliphatic and carbocyclic carboxylic acids some of which bear as substituents chlorine and/or fluorine atoms or hydroxy amino, nitro or methoxy groups. The complexes, which may be partially neutralised if desired, are used in aqueous solution as waterproofing or sizing agents (see Groups III and VIII). In Examples: (1) Solutions of a basic aluminium chloride Al(OH)2.3Cl0.7 in propanol are warmed with various amounts of stearic acid yielding stearato-aluminium chloride complexes having a numerical ratio of stearic acid: metal of 1 : 1-4; (2) the same basic salt is similarly reacted in propanol/isopropanol solution with myristic acid; (3) propanolic solutions of Al(OH)2Cl are reacted with palmitic acid yielding complexes having a palmitic acid: metal ratio of 1 : 2-4. Other similar complexes are described. Methods for preparing the basic ionizable salt starting materials are also described. Specification 784,727 and U.S.A. Specifications 2,273,040, 2,519,983, 2,559,628, 2,559,629 and 2,567,011 are referred to.ALSO:Aqueous colloidal solutions of organic aluminium complexes of the Werner type which comprise negative ions, which are strong inorganic acid anions, and positive complex ions in which nuclear aluminium atoms covalently linked to oxygen atoms in hydroxyl groups and/or to oxygen atoms linked also to other aluminium atoms, the numerical ratio of the oxygen atoms to aluminium atoms being greater than 1:1 but not exceeding 2.5:1, are coordinated with acyloxy groups of monobasic carboxylic acids having a water solubility at 20 DEG C. of less than 1% by weight, the complexes being obtainable in specified manner (see Group IV(b)) may be used to impart water-repellency to inter alia wood, metals, clays, fillers, glass, masonry and other ceramic materials. The dissolved complexes may be partially neutralised and, to facilitate their solution, there may be present low molecular weight organic compounds such as C3-C11 aliphatic ketones and aliphatic alcohols having up to 5 carbon atoms. The complexes may comprise anions of hydrochloric, hydrobromic, hydroiodic, nitric or chloric acid. Numerous suitable carboxylic acids are listed to provide the acyloxy group components including saturated and unsaturated aliphatic and carbocyclic acids some of which are substituted by chlorine and/or fluorine atoms or hydroxy, amino, nitro or methoxy groups. Specified complexes are prepared by reaction of the basic salts Al(OH)2Cl or Al(OH)2,3Cl0,7 with stearic, palmitic or myristic acid and have a numerical ratio of carboxylic acid to metal of 1:1-4. Kaolin clay treated with an aqueous solution of the myristo-aluminium chloride complex and then dried is rendered hydrophobic and dispersible in toluene. Basic ionizable aluminium salts, in which the aluminium is bound partly to hydroxyl groups, and optionally also to oxygen-aluminium linkages and for the rest to strong inorganic acid anions, which have a basicity greater than 33 1/3 % but not more than 83 1/3 % (the salt Al(OH)Cl2 has a basicity of 33 1/3 %) and are used to prepare the complexes, may be obtained by one or other of these methods: (i) reacting an aluminium alcoholate with predetermined amounts of water and the inorganic acid preferably in the presence of an organic solvent; (ii) reacting the aluminium alcoholate with an aluminium salt of the inorganic acid, preferably in an organic solvent, to yield a basic salt Al(OH)2X; (iii) azeotropically dehydrating a hydrated aluminium salt of the inorganic acid with an alcohol; (iv) treating an alcoholic solution of an aluminium salt of the inorganic acid with an anhydrous base or an anion-exchange resin in the hydroxyl form; (v) reacting an aluminium oxide or hydrous aluminium oxide with an anhydrous strong inorganic acid or aluminium salt thereof. The basic salt Al(OH)2,3Cl0,7 is made by azeotropic dehydration of aluminium chloride hexahydrate or by converting the latter into Al(OH)2Cl by reaction with aluminium in water at 90 DEG C. followed by azeotropic dehydration with propanol.