Patent GB-458163-A (GB)
Title: Improvements in or relating to the cleansing of metal articles
IPC: C23G1/02
Filed: 1935-06-12
Abstract: Wetting-agents, for example, naphthalene sulphonic acids, alkylized naphthalene sulphonic acid, or alkylized tetrahydro-naphthalene sulphonic acid, are added to cleansing compositions for removing deposits or incrustations, for example, beer scale or milk scale, from apparatus used in the foodstuffs and table luxuries industries. The cleansing compositions comprise aqueous solutions of acid-reacting stable nitric acid salts of organic compounds containing an NH2 group, for example, solutions of urea nitrate or thiourea nitrate, or nitric acid solutions to which have been added organic compounds containing an NH2 group.  The solutions may be made into pastes by the addition of inert substances such as infusorial earth or kieselguhr, and may contain other neutral or acid constituents, for example, salts such as potassium sulphate or anti-corrosion agents.ALSO:Deposits and incrustations, e.g. beer scale, milk scale, &c., on apparatus used in the foodstuffs and table luxuries industry are removed by treating the affected surface with an aqueous solution of one or more acid-reacting stable nitric acid salts of organic compounds containing an NH2 group, for example the nitrates of urea and thiourea.  The nitric acid liberated reacts with the incrustations and the organic bases react with the decomposition products of the acid and prevent the liberation of oxides of nitrogen.  Instead of using solutions of preformed salts, organic compounds containing an NH2 group may be added to nitric acid solutions, the amount added being determined by the amount and nature of the deposit to be removed.  The solutions may be made into pastes by the addition of inert agents such as infusorial earth or kieselguhr and may contain other substances having a neutral or acid reaction, for example salts such as potassium sulphate, anti-corrosion agents, and wetting agents such as naphthalene-sulphonic acids, alkylized naphthalene-sulphonic acid or alkylized tetrahydronaphthalene - sulphonic acid.  Organic compounds which may be added to nitric acid to form the cleaning solutions include primary aliphatic, cycloaliphatic, aromatic, and heterocyclic amines, substances having a plurality of amino groups, such as ethylene diamine, amino compounds with other substituents such as taurin, amino acids such as glycocoll, alanine, and leucine, and amino compounds of dicarboxyclic acids, for example asparagic acid. Acid amides and sulphonamides, for example formamide, acetamide, benzoic acid amide, benzene or toluene sulphonamide, urea, thiourea, and guanidine, may be used and also substances such as dinitrosodiphenylamine.  Salts and additive compounds of any of the above substances may be employed.  All the compounds react with oxides of nitrogen to form innocuous substances, for example with the evolution of nitrogen, diazo compounds being formed as intermediate products in some cases.  Examples of specific cleansing compositions are given.ALSO:Deposits and incrustations, e.g. beer scale, milk scale, &c., on apparatus used in the foodstuffs and table luxuries industry are removed by treating the affected surface with an aqueous solution of one or more acid-reacting stable nitric acid salts of organic compounds containing an NH2 group, for example the nitrates of urea and thiourea.  The nitric acid liberated, reacts with the incrustations and the organic bases react with the decomposition products of the acid and prevent the liberation of oxides of nitrogen.  Instead of using solutions of pre-formed salts, organic compounds containing an NH2 group may be added to nitric acid solutions, the amount added being determined by the amount and nature of the deposit to be removed.  The solutions may be made into pastes by the addition of inert agents such as infusorial earth or kieselguhr and may contain other substances having a neutral or acid reaction, for example salts such as potassium sulphate, anti-corrosion agents, and wetting agents such as naphthalene-sulphonic acids, alkylized naphthalene-sulphonic acid or alkylized tetrahydronaphthalene-sulphonic acid.  Organic compounds which may be added to nitric acid to form the cleaning solutions include primary aliphatic, cycloaliphatic, aromatic, and heterocyclic amines, substances having a plurality of amino groups, such as ethylene diamine, amino compounds with other substituents such as taurin, amino acids such as glycocoll, alanine, and leucine, and amino compounds of dicarboxylic acids, for example asparagic acid. Acid amides and sulphonamides, for example formamide, acetamide, benzoic acid amide, benzene or toluene sulphonamide, urea, thiourea, and guanidine, may be used and also substances such as dinitrosodiphenylamine.  Salts and additive compounds of any of the above substances may be employed.  All the compounds react with oxides of nitrogen to form innocuous substances, for example with the evolution of nitrogen, diazo compounds being formed as intermediate products in some cases.  Examples of specific cleansing compositions are given.