oward that end.

Most limestones contain some percentage of magnesium, and in the case of
a pure dolomite over 45% carbonate is present in combination with
calcium carbonate. A stone rich in magnesium slakes less readily than
one high in calcium, and therefore is preferred by manufacturers
shipping pulverized burnt lime to reach its destination before slaking.

CHAPTER XV

WHAT SHALL ONE BUY?

_Relative Values._ The relative strengths of the various materials
containing lime may be known and yet doubt continue respecting the
choice to be made. The conflicting claims of dealers, and inaccurate
deductions from a single test made by some individual, aid the
confusion. If there were always the single purpose of correcting soil
acidity, and if there were the same ease of application in case of all
the materials, the choice would present much less difficulty.
Notwithstanding this, most land now has a lime requirement, or will have
one as leaching, crop removal and chemical change within the soil
continue, and the puzzle is no worse than a score of others that present
themselves continuously in farming.

_Destroying Acids._ The cost of liming to improve the physical condition
of land is prohibitive for most farms remote from supplies of stone that
can be burned and put upon the land at a low price per ton. Where stone
is at hand, and soils are intractable, lime burned on the farm should
be used. Some slight benefit to a stiff soil may be obtained from the
light application that is deemed practicable where all forms are costly,
but this benefit is not usually marked in case of an application of a
ton or less of burned lime. It is a safe statement that most buyers of
lime in some form or other will profit chiefly through the correction of
soil acidity and promotion of bacterial life. This renders the situation
more simple as any carbonate, hydrate or oxide of lime will accomplish
these purposes.

_Composition._ The first consideration is the actual content of calcium
and magnesium. A guaranteed analysis is the only safe basis of purchase.
The unstable nature of fresh burned and hydrated forms makes an exact
statement of percentages impossible for goods not wholly fresh, but at
least the purity of the original limestone can be judged.

_Equivalents._ One ton of fresh burned lime, made from pure stone, is
equivalent to 2640 pounds of the hydrate, and to 3570 pounds of
pulverized limestone or of air-slaked lime. It