Superphosphate of Lime: Bones Dissolved in Sulfuric Acid

Bones are mostly phosphate of lime, which hardly dissolves. Sulfuric acid turns part of it into a soluble biphosphate, with gypsum; dried with ashes, the mixture is superphosphate of lime, a fertiliser and a source of phosphorus. Muspratt's chemistry gives Pusey's small-farm method: a heap of crushed bones in a ring of ashes, wetted, acid turned in with a spade, left a week. The picture: a superphosphate works on the Zuid-Willemsvaart canal at Veghel, the Netherlands, from the air.