The Penguin dictionary of science by E.B. Uvarov & Alan Isaacs 6th
edition 1986 ELBS edition ISBN 0140711260 has described basic slag on
page 36 as follows :-
?An impure mixture of Ca4P2O9, CaSiO3, CaO & Fe2O3. A byproduct of
steel manufacture, its high Phosphorus content makes it a valuable
fertilizer.?
      We have got basic slag locally tested & found that it contains
18% w/w Phosphorus as (P2O5) & wish to use it as a substitute for
imported Rock Phosphate for the manufacture of Phosphoric Acid
(H3PO4).
      Normal process for manufacture of  Phosphoric Acid using
imported Rock Phosphate having 30% P2O5 is to dissolve Rock Phosphate
in 98% H2SO4 and get Phosphoric Acid as the filtrate.
      However, the problem is that Basic slag doesnot dissolve in 98%
H2SO4, may be due to the fusion & bonding of Ca4P2O9 with CaSiO3 in
the high temperature zone of the Bessemer Converter!
      Is there any economically viable process to manufacture
Phosphoric Acid (H3PO4) on commercial scale using BASIC SLAG as a
substitute for imported Rock Phosphate?

Actually in Colombia, ACERIAS PAZ DEL RIO S.A, become a program for
increase P2O5 in the basic slag, (10% Soluble Neutral Amoniumm
Citrate) to 30% P2O5 Soluble in NAC, follow the proceed of mix the
colombian rock phosphate (25% P2O5 total) with basic slag of the
converters LWS (1.200°C) and CaSiO3, we expect the increase of the
P2O5 soluble in N.A.C.

Ricardo Florez Escobar
Agronomy