Abstract: A method for the treatment of phosphoric acid containing one or more impurities comprising the ions of at least one of the metals from the group magnesium, iron and aluminium, including the step of heating the acid under such conditions of temperature, pressure, time and concentration as to cause at least some of these impurities, (and in the case where magnesium is the major constituent among such impurities, more than 60% (mass/mass) of such magnesium) to precipitate as a pyrophosphate of the relevant metal ion.

Abstract: A water soluble mixed fertilizer composition in solid form and a method of producing the fertilizer composition. The fertilizer comprises a mixture of urea, phosphoric acid and at least one potassium salt selected from the class comprising potassium sulphate, potassium nitrate and potassium chloride. Ammonium salts selected from the class comprising ammonium nitrate and ammonium sulphate may optionally also be added to the mixtures. Solid fertilizer compositions possible according to this invention include compositions which contain between 5 and 42% nitrogen, between 2 and 15% phosphorus and between 1 and 38% potassium, these values being elemental mass as a percentage relative to the total mass of the composition.