Boiling bones under pressure, whereby their gelatine is dissolved away, and the inorganic matter left in an available condition, from its softness, is a very good way of rendering them useful; but, as it requires, among other things, a steam boiler, it is hardly probable that it will be largely adopted by farmers of limited means.
Any or all of these methods are good, but bones cannot be used with true economy, except by changing their inorganic matter into
SUPER-PHOSPHATE OF LIME.
Super-phosphate of lime is made by treating phosphate of lime, or the ashes of bones, with sulphuric acid.
Phosphate of lime, as it exists in bones, consists of one atom of phosphoric acid and three atoms of lime. It may be represented as
| Phosphoric acid | { | Lime |
| Lime | ||
| Lime |
By adding a proper quantity of sulphuric acid with this, it becomes super-phosphate of lime; that is, the same amount of phosphoric acid, with a smaller proportion of lime (or a super-abundance of phosphoric acid), the sulphuric acid, taking two atoms of lime away from the compound, combined with it making sulphate of lime (plaster). The changes may be thus represented.
| Phosphate of lime | Phosphoric acid | Super-phosphate of lime. | ||||
| Lime | ||||||
| Lime | Sulphate of lime. | |||||
| Lime | ||||||
| Sulphuric acid | ||||||
Super-phosphate of lime may be made from whole bones, bone dust, bone-black, or from the pure ashes of bones.
How should sulphuric acid be applied to whole bones?