Abstract: A process for producing KNO3 from polyhalite to is disclosed. In a preferred embodiment, the process comprises steps of (a) contacting polyhalite with HNO3; (b) adding Ca(OH)2 to the solution, thereby precipitating as CaSO4 at least part of the sulfate present in said solution; (c) precipitating as Mg(OH)2 at least part of the Mg2+ remaining in said solution by further addition of Ca(OH)2 to the remaining solution; (d) concentrating the solution, thereby precipitating as a sulfate compound at least part of the sulfate remaining in solution; (e) separating at least part of the NaCl from the solution remaining; and (f) crystallizing as solid KNO3 at least part of the K+ and NO3-contained in the solution. The process enables direct conversion of polyhalite to KNO3 of purity exceeding 98.5% and that is essentially free of magnesium and sulfate impurities.

Abstract: A method for the production of KNO3 from polyhalite is provided. The method comprises steps of decomposing said polyhalite into syngenite, gypsum, and soluble components, treating the solid decomposition products sequentially with HNO3 and Ca basic compound, precipitating the CaSO4 thus formed, and crystallizing the KNO3 from the solution remaining. The method recovers up to 75% of the potassium present in the raw polyhalite as KNO3 and substantially all of the remainder as a potassium magnesium sulfate salt.

Abstract: A method for the production of KNO3 from polyhalite is provided. The method comprises steps of decomposing said polyhalite into syngenite, gypsum, and soluble components, treating the solid decomposition products sequentially with HNO3 and Ca basic compound, precipitating the CaSO4 thus formed, and crystallizing the KNO3 from the solution remaining. The method recovers up to 75% of the potassium present in the raw polyhalite as KNO3 and substantially all of the remainder as a potassium magnesium sulfate salt.

Abstract: A process for producing KNO3 from polyhalite to is disclosed. In a preferred embodiment, the process comprises steps of (a) contacting polyhalite with HNO3; (b) adding Ca(OH)2 to the solution, thereby precipitating as CaSO4 at least part of the sulfate present in said solution; (c) precipitating as Mg(OH)2 at least part of the Mg2+ remaining in said solution by further addition of Ca(OH)2 to the remaining solution; (d) concentrating the solution, thereby precipitating as a sulfate compound at least part of the sulfate remaining in solution; (e) separating at least part of the NaCl from the solution remaining; and (f) crystallizing as solid KNO3 at least part of the K+ and NO3-contained in the solution. The process enables direct conversion of polyhalite to KNO3 of purity exceeding 98.5% and that is essentially free of magnesium and sulfate impurities.

Abstract: Compounds of the formula: ##STR1## wherein: n=0 or 1;R.sub.1 and R.sub.2 are C.sub.1 to C.sub.3 alkyl groups, or R.sub.2 may be H when n=0; and Y is selected from the group: ##STR2## wherein: m=1-6Z=SO.sub.2, S, C=O, CH.sub.2 or C(CH.sub.3).sub.2 ; and a process for their preparation are described.

Abstract: Diaminodiphenyl-compounds of the structure selected from: ##STR1## wherein R.sub.1 and R.sub.2 can be: H, --CH.sub.3, --C.sub.2 H.sub.5, --C.sub.3 H.sub.7, --C.sub.4 H.sub.9 or ##STR2## Y can be: C(CH.sub.3).sub.2, ##STR3## n=0; 1. are purified by distilling the crude product obtained under vacuum in one step, in the presence of one or more alkaline bases.