Organic materials such as hydrophobic substances containing oils, fats or waxes, such as edible oils or fats, candles, floor polishes, floor stains or other wood stains, furniture polishes, dyed and natural soaps are protected against ultra-violet light by the incorporation of a hydroxy mono-ketone of the formula R2 CO R1, where R1 is a residue of the benzene series containing a hydroxyl group ortho to the -CO-group, and R2 is a pyridine ring, which may be substituted, attached directly to the -CO- group, or a salt thereof (see Group IV(b)).  In an example, a lacquer consisting of a stabilized polyvinyl chloride, dioctyl phthalate, methylethyl ketone and toluene is mixed with a solution of a lightscreening agent as above and copper phthalocyanine-tetramethoxy-propylsulphonamide in acetone, and tin foil is coated with the composition.ALSO:Organic materials are protected from ultraviolet light by incorporating or treating with a hydroxy monoketone of formula R2COR1, where R1 is a residue of the benzene series containing a hydroxyl group ortho to the -CO-group, and R2 represents a pyridine ring, which may be substituted, attached directly to the -CO-group, or a salt thereof (see Group IV(b)).  Organic materials specified include textile materials of semi-synthetic or synthetic type, such as regenerated cellulose, e.g. viscose rayon, and polyacrylonitrile, polyesters and polyamides; lacquers and films, e.g. of acetyl cellulose, cellulose propionate, cellulose butyrate and mixed cellulose esters, nitro cellulose, vinyl acetate, polyvinyl chloride, copolymers of vinyl chloride and vinylidene chloride, alkyd resins, polyethylene, polyamides, polyacrylonitrile, and polyesters; natural and synthetic resins, e.g. epoxy resins, polyester resins, vinyl resins, polystyrene resins, alkyd resins and aldehyde resins, such as condensation products of formaldehyde with phenol, urea or melamine, and emulsions of synthetic resins; synthetic resins reinforced with glass fibres and laminates made therefrom; natural rubber-like materials, such as rubber, balata, and guttapercha; and synthetic vulcanizable materials such as polychloroprene, olefinic polysulphides, polybutadiene, and copolymers of butadiene with styrene or acrylonitrile.  The rubber-like materials may contain fillers, pigments, vulcanisation accelerators and other products. The light-screening agents may be added to spinning masses, e.g. polyamide melts or polyacrylonitrile spinning masses, and may be added before, during or after the polymerization.  In an example, a lacquer consisting of a stabilized polyvinyl chloride, dioctylphthalate, methylethyl ketone and toluene is mixed with a solution of a light-screening agent as above and copper phthalocyanine-tetramethoxy-propyl-sulphonamide in acetone, and the composition is used to coat tin foil.ALSO:The invention comprises hydroxy monoketones of formula R2COR1, where R1 is a residue of the benzene series containing a hydroxyl group ortho to the-CO-group, and R2 is a residue containing the structure <FORM:0880549/IV (b)/1> this ring being bound directly to the-CO-group; salts of such compounds; and their manufacture by reacting an acyl halide R2CO halogen in the presence of a Friedel-Crafts catalyst, or an acid R2COOH in the presence of a boron fluorine compound, with a compound of the benzene series containing at least one hydroxyl group (which may be etherified); or a hydroxyl compound of the benzene series is esterified with the acyl halide R2CO halogen and the ester is rearranged to the hydroxy-ketone by treatment with a Friedel-Crafts catalyst.  The basic compounds may be converted into salts, and/or treated to introduce sulphonic acid, sulphonic acid amide or tertiary amino methyl groups by known methods, e.g. treatment with oleum to obtain sulphonic acids, which can be converted to halide and treated with ammonia or primary or secondary amines to form sulphonic acid amides; or by treatment with an aldehyde or an agent yielding an aldehyde and a secondary amine such as dimethylamine, diethylamine, piperidine or morpholine.  The hydroxyketones may also be nitrated, the nitro groups reduced to amino groups, and the latter alkylated or acylated.  Preferred compounds have the formulae <FORM:0880549/IV (b)/2> where m and n are 1, 2 or 3 and m + n is at most 4; and <FORM:0880549/IV (b)/3> Specific examples and lists of suitable starting materials are given.  The compounds of the invention are of use as ultra-violet screening agents.ALSO:Textile materials are protected from ultraviolet light by incorporating or treating with an hydroxy monoketone of formula R2COR1, where R1 is a residue of the benzene series containing a hydroxyl group ortho to the -CO- group, and R2 represents a pyridine ring, which may be substituted, attached directly to the -CO- group, or a salt thereof (see Group IV(b)). Materials specified are wool, silk, cotton, hemp, flax, linen, jute and ramie; semi-synthetic materials such as viscose rayon, and synthetic materials such as polyacrylonitrile, polyesters and polyamides.  The materials may be in the form of fibres, filaments, yarns, woven or knitted fabrics or felt, or the finished products made therefrom.  The compounds may be incorporated in coating and dressing agents for textiles, e.g. those based on starch, casein, vinyl acetate or derivatives of acrylic acid.ALSO:Butter and other edible fats can be preserved against ultra-violet light by incorporating a hydroxy monoketone of formula R2CO R1, where R1 is a residue of the benzene series containing a hydroxyl group ortho to the- CO- group, and R2 represents a pyridine ring, which may be substituted, attached directly to the- CO- group, or a salt thereof (see Group IV(b)).ALSO:Fibrous materials, edible oils and fats, and cosmetics are protected from ultra-violet light by treatment with or incorporation of an hydroxy monoketone of formula R2COR1, where R1 is a residue of the benzene series containing an hydroxyl group ortho to the -CO- group, and R2 represents a pyridine ring, which may be substituted, attached directly to the -CO-group, or a salt thereof (see Group IV (b)).  Specified materials for protection include feathers, hairs, pelts, hides, straw, wood, woodpulp; and perfumes, bath salts, dyed or natural soaps, skin and face creams, powders and repellents.  The cosmetic preparations are antisunburn compositions, and examples prepare compositions containing, in addition to the screening agent, adipic acid isopropyl tetrahydrofurfuryl ester, glycerine monostearate and ethanol; ethanol, perfume oils, trichlorofluoromethane and dichlorodifluoromethane; adipic acid isopropyl tetrahydrofurfuryl ester, benzoic acid diethylamide, dimethylphthalate, ground nut oil and paraffin oil; and glycerine monostearate, cetyl alcohol, sodium cetyl sulphate, stearic acid, glycerine and water.