Press Bulletin No. 5.
July 1, 19o1.
Florida Experiment Station.
Basic slag is obtained as a by-product from the man-
ufacture of steel by the Bessemer process. It contains
from 15 to 25 per cent. of phosphoric acid in a form not
found in other materials containing phosphoric acid.
In acid phosphate the phosphoric acid which is regarded
available is present as monocalcium phosphate and as di-
calcium phosphate; the first being soluble in water, and
the second soluble in amonium citrate. The phosphoric
acid in the untreated Florida rock is in the form of tri-
calcium phosphate and is supposed to be only very slowly
available to plants, On the other hand, the greater por-
tion of the phosphoric acid in basic slag is in the form of
tetracalcium phosphate. In this form the phosphoric
acid is largely available oi certain soils.
In Eglaind, Franco and G(rimany this material has
been used for a nitumber of years as a p1)h1sphatic manure
with very satisfactory results. In Germany such great
success has attended its use that at present the amount
consumed is probably greater than that of acid phosphate.
In America basic slag has been used somewhat extensively
in Canada with fair prospects of its use becoming much
more general in the immediate future. A great deal of
the slag has not been used in the United States up to the
present time, but it is beginning to find its way into the
markets and it will unquestionably soon become an article
of great agricultural value with ,us as it now is with the
Germans. The slag produced in tlhi country is made at
Pottstown, 'Pennsylvania, under the patents of Jacob
Reese and is known on the market as odorless phosphate.
The process of nainufacture in brief is as follows:
The molten pig iron which is to be made into stool is run
into the converter and a suitable quantity of lime added.
A blast of air is forced through the ironl which burns out
the carbon and converts the phosphorus into phosphoric
acid. The heat becomes so intense that the lime melts
and unites with the phosphoric aci(d and other impurities
forming the ,I-:. while the iron is converted into steel.
The slag is poured ot' and ground to a very fine powder
and' is ready for market. As might be expected from the
process of manufacture, the composition" of the slag is
variable. But it nearly always contains a considerable
amount of free lime.
It is expected that the prepared slag will soon be
made in Birmingham, Alabama. In this case it can be
placed in Florida at less cost than at present. According
to the German estimates, more than half the phosphoric
acid is available, .and at present the slag is quoted at
about half the price of acid.phosphate.
A number of oxporiments.have been made with Basic
slag in this country by the experiment statiofis, and in
many cases the results obtained with it were better than
those from any other phosphatic material. I do not
think it would be advisable to use the slag on our poor
sandy soils, devoid of vegetable matter, but there is no
reason why it will not yield good results on our hammock
lands and muck soils. One thing which commends it for
such soils is the free lime it contains, which will aid ma-
terially in neutralizing 'the free acid present in these
soils. The slag-may prove a valuable fertilizer for pine-
apples. We are in great need of a cheap phosphatic ma-
terial for this fruit since acid phosphate cannot be used
without injury to the crop.
The station is preparing to undertake some experi-
ments with the slag on pineapple plots, the results of
which will be awaited with interest. H. K. MILLER.