Abstract: A process is described for producing high purity phosphoric acid of 40% P.sub.2 O.sub.5 concentration from phosphate rock. The process is controlled to achieve the desired results by monitoring and controlling the sulfuric acid content at various processing stations resulting in the control of gypsum formation and the minimization of freed impurities in the phosphate rock.

Abstract: A process is described for highly efficient recovery of phosphate values from a wide range of phosphate rock including low grade phosphate rock material by leaching with a dilute sulfuric acid and precipitating phosphate values as dicalcium phosphate. Water savings are accomplished in the process by the use of sea water instead of fresh water.

Abstract: A method of making phosphoric acid and gypsum through a precipitated phosphate intermediary which comprises mixing a precipitated dicalcium phosphate with a highly dispersed reaction admixture of sulfuric acid and phosphoric acid, at a temperature between about 25.degree. and 80.degree. C; and withdrawing and separating phosphoric acid containing up to about 45% or more P.sub.2 O.sub.5 and gypsum containing generally less than 0.25% P.sub.2 O.sub.5. The resultant gypsum is highly filterable and very low in occluded phosphate value. Preferably, the process involves first obtaining a weak phosphoric acid solution from and by leaching as-mined phosphate mineral containing material to obtain the precipitated dicalcium phosphate; and then converting the precipitated phosphate by the process to the strong phosphoric acid solution.

Abstract: A process is described for producing high purity phosphoric acid from phosphate rock including low grade phosphate rock material such as Idaho phosphate ores having P.sub.2 O.sub.5 contents as low as 20 percent. Finely divided phosphate rock, sulfuric acid, phosphoric acid and water are charged to a mixing zone in proportions such that the pH of the resultant slurry is in the range 0.8 to 1.2 and the calcium ion content of the liquid phase of the slurry is in the range 3 to 4 percent by weight. Sulfuric acid is charged to the mixing zone in a quantity sufficient to convert the nonphosphate calcium compounds in the rock to calcium sulfate plus the quantity required to convert the contained calcium phosphate to monocalcium phosphate, phosphoric acidis charged to the mixing zone in quantities such that it is, on a molar basis, from about 1.2 to about 1.4 times the P.sub.2 O.sub.