Superphosphate is a fertilizer produced by the action of concentrated sulfuric acid on powdered phosphate rock.

Ca3(PO4)2 + 2H2SO4 → Ca(H2PO4)2 + 2CaSO4

History and development

In the 1840s, scientists found that coprolites could be dissolved in sulfuric acid to produce what became known as superphosphate.

In 1840, Justus Von Liebig wrote, "The crops on the field diminish or increase in exact proportion to the diminution or increase of the mineral substances conveyed to it in manure." Von Liebig was the first to discover that phosphate of lime in bone meal could be rendered more readily available to plants by treatment with sulfuric acid. Sir John Bennett Lawes about the same time discovered that phosphate rock underwent the same reaction and could be used as a source ingredient.

Simply put, insoluble tricalcicphosphate is converted to soluble monocalcicphosphate by reaction with sulphuric acid.

Bennett Lawes was the first to manufacture superphosphate at his factory in Deptford, England in 1842. A large market for superphosphate was created in the second half of the 20th century by the development of aerial topdressing in New Zealand which allowed superphosphate to be spread economically over large areas.

References

• Yara corporate History Accessed May 2007

External links