Abstract: A method for the manufacture of physically prepared slow-release fertilizer by coating fertilizer particles with at least one layer of a substantially water insoluble metal salt formed in-situ from an organic acid having between 6 and 30 carbon atoms and a metal oxide or carbonate. Optionally, the coating layer contains micronutrients and inert materials. In a preferred embodiment, an additional layer of paraffin is added on the coating of metal salt of organic acid. The method is applicable for most of the known fertilizers. The method enables to vary the rate of fertilizer release and the release period time according to specific requirements.

Abstract: The present invention relates to a process for the manufacture of monopotassium phosphate using solvent extraction technique. According to the invention, the reaction occurs between phosphoric acid and potassium chloride at a temperature between 0 and 100 degrees C. in the presence of an organic solvent comprising a long chain primary amine having between 6 to 28 carbon atoms. The lower phase containing monopotassium phosphate and dipotassium phosphate is acidulated with a solution of phosphoric acid to a pH in the range of between 2 to 6, whereby crystallized monopotassium phosphate is obtained and separated. The upper phase which contains the organic solvent, aminehydrochloric acid as well as most of the impurities originally present in the starting reagents, is treated with a base at a temperature in the range of 20 to 100 degrees C. whereby the amine is regenerated and recycled to the process. Typical examples of suitable bases are calcium oxide, calcium carbonate or mixtures thereof.

Abstract: The present invention relates to a process for the manufacture of potassium nitrate from potassium chloride and nitric acid. According to the invention, potassium chloride and nitric acid are reacted in an aqueous medium at a temperature in the range of between -25.degree. C. to +10.degree. C. From the brine solution obtained after the separation of the resulting potassium nitrate, nitric acid is extracted by an organic solvent solution containing at least one compound selected from the group consisting of ketones having five to ten carbon atoms, straight or cyclic polyethers having molecular weight in the range of 100 to 1000, polyalkylene glycols slightly miscible in water and having molecular weight in the range of 1000 to 3000, and organic esters of phosphoric acid, phosphonic acid and phosphinic acid, or mixtures thereof, in an organic diluent which does not substantially extract hydrochloric acid. The remaining aqueous solution consists of a substantially nitrate-free brine containing hydrochloric acid.

Abstract: The present invention relates to a process for the manufacture of potassium nitrate with co-production of relatively concentrated aqueous solution of hydrochloric acid.According to the invention, potassium chloride and nitric acid are reacted in the medium of an organic solvent selected from butanols and pentanols. The solution obtained after the separation of the resulting potassium nitrate, containing hydrochloric acid together with nitric acid and said organic solvent, is subsequently washed thus resulting an aqueous solution of hydrochloric acid which contains nitric acid. The nitric acid is extracted by an organic solvent selected from organic esters of phosphoric acid, ketones having five to ten carbon atoms and straight or cyclic polyethers having molecular weight in the range of 100 to 1000 and polyalkylene glycols which are slightly miscible in water and having molecular weight in the range of 1000 to 3000, or mixtures thereof, preferably in the presence of an organic diluent.