Ca₃(PO₄)₂
by Fermento· from Recipe For Cremation
Bone dust, bone black,
Or phosphorite with sulphuric acid,
Whereby the insoluble neutral calcium
Phosphate, Ca₃(PO₄)₂, is changed to the primary or acid
Calcium phosphate Ca₃(PO₄)₂,
Which is soluble and therefore available for the soil.