The following substances are used as disinfecting or preserving agents: (1) quaternary pyridines of the formula <FORM:0479925/IV/1> (ii) a - or g -amino-pyridines of the formula <FORM:0479925/IV/2> <FORM:0479925/IV/3> (iii) pyridonimides of the formula <FORM:0479925/IV/4> <FORM:0479925/IV/5> In these formulae Y represents hydrogen or any desired residues which may be the same or different, R any desired organic residue, X any desired organic or inorganic anion and R1, R2, hydrogen or the same or different organic residues. The compounds may be used in pure or crude state, as the free bases or their salts, in solution in water or organic solvents, e.g. in alcoholic solution, or in admixture with one another. The mixtures may be prepared from admixtures of the parent materials. They may also be used in the form of mixtures or emulsions with other indifferent or active substances. Many of the compounds have a wetting, foaming and emulsifying capacity. The following quaternary pyridines are mentioned: the addition products of alkyl halides and pyridine, for example, do-, tetra- and octadecyl pyridinium chloride, and cetyl pyridinium chloride; the addition products of alkyl halides and pyridine homologues, for example, cetyl-a -picolinium chloride, cetyl-g -n propylpyridinium chloride, tetradecyl-g -isoamylpyridinium chloride; compounds produced by combining pyridine or its homologues with a compound containing an oxy-group such as ethylene chlorhydrin or a -chlorhydrin, and then esterifying the oxy-group, for example, with lauric, myristic, stearic or oleic acid; compounds produced by combining a pyridine with an amide produced by conversion of an amine such as dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, or a 2-alkoxy-5-aminopyridine into an amide of a halogen carboxylic acid such as chloracetic acid. In the case of the a - and g -amino pyridines, the residues R1, R2 may be linked to the nitrogen atom in the manner of an amine in the case of alkyl, cycloalkyl, aralkyl, aryl or heterocyclic groups, or in the manner of an amide in the case of radicals of saturated or unsaturated fatty acids or cycloaliphatic, aromatic-aliphatic, aromatic or hetero-cyclic acids. The residues R, R1, R2, may be substituted by halogen atoms, ether, thioether or amino-groups, or their carbon atoms may be interrupted by other atoms. The amino-pyridines may be formed from the following reactants: (i) a quaternary a - or g -halogen pyridine or other suitable pyridine derivative and an amine derivative; (ii) a compound R--X and an a - or g -amino pyridine; (iii) a compound R2--X (for example, an alkyl or aralkyl halide or an acid halide) and an a - or g -pyridonimide. If R1 and/or R2 is hydrogen, the pyridonimides are formed from the amino-pyridines with loss of water or acid. Other examples of suitable compounds are:--N-methyl - a - pyridone stearoylimide hydrochloride; N - methyl - a - pyridone cetylimide hydrochloride; a - cetylbenzylamino - N-methyl - pyridinium bromide (prepared by reacting N - methyl - a - pyridone - cetylimide with benzyl bromide); a -phenyl-stearoylamino N-methyl pyridinium chloride (obtained by reacting stearic acid chloride with N-methyl-a -pyridone phenylimide, dissolving in water and precipitating with dilute hydrochloric acid); a -naphthyl - nonylamino - N - methyl-pyridinium chloride (obtained by reacting n-nonylic acid chloride with N-methyl-a -pyridone-naphthylimide and purifying with ether); N cetyl pyridinium chloride; N cetyl-a -picolinium chloride; reaction product of cetyl chloride and g -piperidino-pyridine (apparently g -piperidino-N-cetyl pyridinium chloride) reaction product octadecyl chloride and g -diethylamino-pyridine (apparently g -diethylamino-N-octadecylpyridinium chloride); addition product of dimethyl sulphate and 3-stearoylamino pyridine (apparently 3-stearoylamino-N-methyl - pyridinium metho-sulphate).ALSO:The following substances are used as disinfecting or preserving agents: (1) quaternary pyridines of the formula <FORM:0479925/III/1> (ii) a - or g -amino-pyridines of the formula <FORM:0479925/III/2> or <FORM:0479925/III/3> (iii) pyridonimides of the formula <FORM:0479925/III/4> or <FORM:0479925/III/5> In these formulae Y represents hydrogen or any desired residues which may be the same or different, R any desired organic residue, X any desired organic or inorganic anion and R1, R2, hydrogen or the same or different organic residues. The compounds may be used in pure or crude state, as the free basis or their salts, in solution in water or organic solvents, e.g. in alcoholic solution, or in admixture with one another. The mixtures may be prepared from admixtures of the parent materials. They may also be used in the form of mixtures or emulsions with other indifferent or active substances. Many of the compounds have a wetting, foaming and emulsifying capacity. The following quaternary pyridines are mentioned: the addition products of alkyl halides and pyridine, for example, dotetra- and octadecyl pyridinium chloride, and cetyl pyridinium chloride; the addition products of alkyl halides and pyridine homologues, for example, cetyl-a -picolinium chloride, cetyl-g -n propylpyridinium chloride tetradecyl-g -isoamylpyridinium chloride; compounds produced by combining pyridine or its homologues with a compound containing an oxy-group such as ethylene chlorhydrin or a -chlorhydrin, and then esterifying the oxy-group, for example, with lauric, myristic, stearic or oleic acid; compounds produced by combining a pyridine with an amide produced by conversion of an amine such as dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, or a 2-alkoxy-5-aminopyridine into an amide of a halogen carboxylic acid such as chloracetic acid. In the case of the a - and g -amino pyridines, the residues R1, R2 may be linked to the nitrogen atom in the manner of an amine in the case of alkyl, cycloalkyl, aralkyl, aryl or heterocyclic groups, or in the manner of an amide in the case of radicals of saturated or unsaturated fatty acids or cycloaliphatic, aromatic-aliphatic, aromatic or hetero-cyclic acids. The residues R, R1, R2, may be substituted by halogen atoms, ether, thioether or amino-groups, or their carbon atoms may be interrupted by other atoms. The aminopyridines may be formed from the following reactants: (i) a quaternary a - or g -halogen pyridine or other suitable pyridine derivative and an amine derivative; (ii) a compound R--X and an a - or g -amino pyridine; (iii) a compound R2--X (for example, an alkyl or aralkyl halide or an acid halide) and an a - or g -pyridonimide. If R1 and/or R2 is hydrogen, the pyridonimides are formed from the aminopyridines with loss of water or acid. Other examples of suitable compounds are:--N-methyl - a - pyridone stearolyimide hydrochloride; N - methyl - a - pyridone cetylimide hydrochloride; a - cetylbenzylamino - N-methyl - pyridinium bromide (prepared by reacting N - methyl - a - pyridone - cetylimide with benzyl bromide); a -phenyl-stearoylamino-N-methyl pyridinium chloride (obtained by reacting stearic acid chloride with N-methyl-a -pyridone phenylimide, dissolving in water and precipitating with dilute hydrochloric acid); a -naphthyl - nonylamino - N - methylpyridinium chloride (obtained by reacting n-nonylic acid chloride with N-methyl-a -pyridone-naphthylimide and purifying with ether); N-cetyl pyridinium chloride; N-cetyl-a -picolinium chloride; reaction product of cetyl chloride and g -piperidino-pyridine (apparently g -piperidino-N-cetyl pyridinium chloride) reaction product octadecyl chloride and g -diethylamino-pyridine (apparently g -diethylamino-N-octadecylpyridinium chloride); addition product of dimethyl sulphate and 3-stearoylamino pyridine (apparently 3-stearoylamino-N-methyl - pyridinium metho-sulphate).ALSO:The following substances are used as disinfecting or preserving agents: (1) quaternary pyridines of the formula <FORM:0479925/VI/1> (ii) a - or g -amino-pyridines of the formula <FORM:0479925/VI/2> (iii) pyridonimides of the formula <FORM:0479925/VI/3> In these formulae Y represents hydrogen or any desired residues which may be the same or different, R any desired organic residue, X any desired organic or inorganic anion and R1, R2, hydrogen or the same or different organic residues. The compounds may be used in pure or crude state, as the free bases or their salts, in solution in water or organic solvents, e.g. in alcoholic solution, or in admixture with one another. The mixtures may be prepared from admixtures of the parent materials. They may also be used in the form of mixtures or emulsions with other indifferent or active substances. Many of the compounds have a wetting, foaming and emulsifying capacity. The following quaternary pyridines are mentioned: the addition products of alkyl halides and pyridine, for example, dotetra- and octadecyl pyridinium chloride, and cetyl pyridinium chloride; the addition products of alkyl halides and pyridine homologues, for example, cetyl-a -picolinium chloride, cetyl-g -n propyl-pyridinium chloride, tetradecyl-g -isoamylpyridinium chloride; compounds produced by combining pyridine or its homologues with a compound containing an oxy-group such as ethylene chlorhydrin or a -chlorhydrin, and then esterifying the oxy-group, for example, with lauric, myristic, stearic or oleic acid; compounds produced by combining a pyridine with an amide produced by conversion of an amine such as dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, or a 2-alkoxy-5-aminopyridine into an amide of a halogen carboxylic acid such as chloracetic acid. In the case of the a - and g -amino pyridines, the residues R1, R2 may be linked to the nitrogen atom in the manner of an amine in the case of alkyl, cycloalkyl, aralkyl, aryl or heterocyclic groups, or in the manner of an amide in the case