Gainesville daily sun. (Gainesville, Fla.) 190?-1938, 1908-01-11
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GROUND PHOSPHATE ROCK AS
A SOURCE OF PAOSPAOHIC ACID
BY A. BLAIR, Of Florida Agricultural Experiment station
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phosphate Rock and supsrphospha


NPhosphNts Rock and suPsrphOsphsts.
Tricalcium phosphate is the cheml-
cal name OF the phosphate rock Of
commerce. before It has been treated
with an acid. II Is found In Florida,
South Carolina, Tennessee, and to
some extent In other places in the
United States. When this rock Ia
ground very finely and placed on the
market without any further treatment,
Il is usually spoken Of rs ground phos-
plate rock, or floats" In this form
II has, by many, been regarded az
practically insoluble In the soil solu.
lions and therefore not available for
plant food. For this reason the great.
er portion Of the rock that Is used is
treated with a strong acid-sulphuric
acid-which converts the phosphoric
acid into a form that Is soluble In
water-the monocalcium phosphate,
The resulting material is placed upon
the market as acid phosphate" some
times called superphosphate, or su.
perphosphate of lime. Expressed In
the form OF an equation the reaction
Is as follows: Tricalcium phosphate
$40 parts plus sulphurlc acid 1876 parts,
equals monocalcium phosphate 234
parts plus calcium sulphate (land plas-
teri 272 parts,
Acid Phosphate Readily Available.
Acid phosphate usually contains
from IL to l6 per cent of phosphorlc
acid most OF which Is regarded as
available. But the treatment OF rock
phosphate with acid Is expensive. and
on this account lt becomes necessary
to sell the acid phosphate for con-
siderable more per ton than the
ground rock (hOats) would cost, al.
though the latter contains about
twice as much phosphoric acid per
ton as Is contained in the treated rock
(acid phosphate). Tho phosphoric
acid OF the treated rock has the Rd.
vantage OF being largely soluble, and
Ia therefore much more readily avail.
able than the phosphoric acid In the
floats
Ground Phosphate Rock Slowly Avail
able,
However, II IL a fact that the phos.
puoFlc acid OF floats does become
slowly available. the availability be-
ing somewhat proportional TO the fine
ness OF the material and the amount
Of organic matter In the soil. In a
soil containing much humus II will
become available more rapidly than
In one that IL deficient in this respect,
An acid soil also tends to hasten its
availability. the acid condition OF the
soil being gradually corrected At the
same time Ut shoHld be borne in
mind however. that this is a rather
slow way Of correcting an acid soil, II
the correcting Of acldity alone II tho
result to be attained.l Experiments
have shown that water charged with
carbon dioxide gas haS a solvent Of.
feet upon phosphate rock. and since
the ground waters OF Florida are
more or less charged with this Eas
(their solvent effect upon the lime
stone formation II . proof Of ~. Ws
might reasonably expect that some Of
the phosphoric acid Of the phosphate
rock would be- made available In this
way.
Many experiments have been con.
Quoted throughout the United States
which give evidence that the phoa.
phoric acid Of floats does become SLOW.
~ available. and a few places may b.
Rhode Island and Mary.
land--vhere this ground phosphate
rock has given results As good -. II
not better than. the other forms Of
acid
Ground Phosphate Rock . Permanent
Investment /
The application of . ton oF tuo I
Of HneIy ground phosphate rOck per
acre Nigh, BE- Ionked upon az . per
mancnt lnvestmont rather than an i'm
mediate fertilizer ., would ceFtAlaly
pot 30 easily boat. bot. on The other
haad would Ae' a. q sourcP a Tbos.
phoric acid FOR number q Year,
For the first tao % three years u