Abstract: A layer of bare, untreated phosphate rock granules is applied to the soil, and concentrated sulfuric acid is supplied thereto. The sulfuric acid is sufficiently concentrated so as to be containable by cold-rolled carbon steel, and sufficiently viscous to cling to the granules to react therewith. Sulfuric acid in excess of the amount needed for reaction with the phosphate rock can be added to correct alkaline conditions in the underlying soil. The reaction of sulfuric acid with the phosphate rock produces substantial quantities of available phosphate and gypsum.

Abstract: A sulphur-burning and gaseous products absorption system incorporating control means to establish generation of sulphur dioxide at a rate which is compatible with the capacity of absorption means for absorption of the gases by water, together with controls which make the system fail-safe even when unattended. In order to provide an absorption efficiency compatible with clean air standards, a unique absorption tower is provided, together with pre-cooling means further to improve the absorption tower efficiency. Further, the control efficiency and the purity of the product are improved by ebullition control. A unique joint is provided for sealing the sulphur-burning tower against undesirable leakage which also enables this tower readily to be disassembled for maintenance and repair.

Abstract: Pulverized phosphate rock is spread onto or mixed into soil which is to be fertilized. The soil is then treated with a solution of sulfurous acid, usually the output of a device which burns sulfur in air to form sulfur dioxide and then dissolves the sulfur dioxide in water. The water may be irrigation water which thereupon both irrigates the soil and reacts with the phosphate rock to fertilize the soil. Common phosphate ores include a substantial amount of calcium, with which, and with oxygen, the sulfurous acid reacts to form gypsum (calcium sulfate). Gypsum is a widely-used corrective substance applied to croplands, and the gypsum formed by this treatment reduces the requirement to purchase gypsum as a product separate from the fertilizer. Substantially all of the phosphorus contained in the rock can ultimately be solubilized as "available phosphate", with the use of this process.