The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1882-02-25
GIlt @arnler.
Lime and Limestone.


An Agricultural Engineer writes to the
Country Geatlenea as follows Consider
able interest is Just now manifested in re-
gard to ground raw limestone as fertilizer.
It is claimed that it is equally as effective
as lime, and some remarkable statements
have been made as to the results in the
shape of large crops grown by Its use.
Now while have no reason to doubt the
truth of these statements, and dc not pro-
fess to impugn them in the least, yet it Is
right that some one shonld explain to your
readers why raw limestone cannot possibly
be as effective as lime, or even as air slaked
lime unless the latter has been exposed for
sufficient time to have completely lost its
causticity and become thoroughly carbonat-
ed again.
Limestone is carbonate of lime, and is
insoluble in water unless the latter contains
some carbonic acid, when it is only slightly
soluble. But as all water in the soil takes
up some carbonic acid from decaying vege
table matter into solution, limestone Is
nearly always dissolved to small extent in
the water, sufficient at least to make the
water hard or refuse to dissolve soap.
When limestone is burned, the carbonic
acid contained in it is driven off, the stone
losing nine-twentieths or 40 per cent. of
its weight. The lime is an acrid, burn
ING, caustic substance which has some, pc
culiar properties upon which its agricul-
tural value depends.
These are, first, that it has great af6-
nifty for carbonic acid, a great eagerness to
recover what it has lost, and to return to
its first and stable condition again. Sec
ond, that it has also a great ayidity of water,
of which it will absorb about one-third of
its weight, and yet remain perfectly dry.
Third, that in thus absorbing water It falls
to am exceedingly fine powder, by which its
action upon organic substances is greatly
assisted II is then called "air-slaked, If
this water is absorbed from the atmosphere.
Fourth. that in this condition it is soluble
in 7eA times its volume Of water, and when
thus dissolved its chemical action is still
further assisted. Fifth, that eaustie lime
exerts very active decomposing effect
upon organic matter, depriving it of car
bonic acid and nitrogen, absorbing the one
and driving off the other, or entering into
some complicated combination with it, and
in effect rapidly reducing it to final decom-
position and its mineral elements. Sixth,
that it also has the property Of dissolving
silica, and thus freeing potash from its
combination as silicate Of potash in the soil,
and leaving it free to be dissolved in water
and taken up as food by the roots Of plants.
Lastly, it exerts favorable effect upon
both clay and sandy soils, looseniRg the one
and compacting the other in texture, both
mechanically, and by its chemical action.
Now these most important eifectsof lime
give it very great value, and render i
one Of the most indispensable aids to the
farmer. But on the other hand limestone
being chemically inert and only slightly so
lnble. can have but very feeble effect, If
any; and, as must be obvious, none at all
where the soil is already charged with lime;
while lime BY its varied chemical action has
rs great an effect upon limestone soils as
upon peaty, mueky or alluvial soils. Some
confusion Of ideas exists as to the term ''air
slake4l, This really means that the lime
has been exposed to the moist air, until it
has absorbed sufficient water % fall 70 a
fine powder, and become hydrate Of lime
But this hydrated lime is still caustic, and
retains all its chemical activity, unless the
exposure has been 50 long that the lime has
also regained its caTbouie acid, But this
required very long time-years in fact
and the lime sold under the name of ''agri-
cultural lime, and really the small broken
waste lime Of the lime kilns, yet retains the
most Of its caustic quality after il has lain
about the kilns for several months So
that there is fresh air slaked lime, which
is pure hydrate Of lime and old air slaked
lime. which has become carbonsted or
mild to a less or greater extent.