em _always wet_. If they become too dry they
will throw off an offensive odor, accompanied by the escape of ammonia,
and consequent loss of value. In about one year, the whole mass of bones
(except, perhaps, those at the top) will be softened, so that they may
be easily crushed, and they are in a good condition for manuring. The
ashes are, in themselves, valuable, and this compost is excellent for
many crops, particularly for Indian corn. A little dilute sulphuric
acid, occasionally sprinkled on the upper part of the matter in the
cask, will prevent the escape of the ammonia.

[What is the effect of boiling bones under pressure?

How is super-phosphate of lime made?

Describe the composition of phosphate of lime, and the chemical changes
which take place in altering it to super-phosphate of lime.]

_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

{ Lime
Phosphoric acid { 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.

{Phosphoric acid} Super-phosphate
Phosphate of lime {Lime } of lime.
{Lime}
{Lime} Sulphate of 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?

What is the necessity for so large an amount of water?]

The process of making it f