Published online by Cambridge University Press: 27 March 2009
1. Two basic slags differing widely in solubility and phosphate content have been treated for long periods with boiling ammonium chloride solution.
2. The low-grade slag lost 70 per cent. of the total lime and very little phosphoric acid; a residue with nearly 40 per cent. phosphate was obtained from an 18 per cent. slag.
3. The high-soluble slag also lost a large percentage of the total lime but large amounts of phosphoric acid were also found in solution. The residue from the 30 per cent. slag after 24 hours' treatment contained nearly 46 per cent. phosphate.
4. It is shown that a silico-phosphate is present in the high-soluble slag, but not in the low-grade slag.
5. The solubility in citric acid of the phosphates in the various residues has been determined.
6. The value of basic slags in supplying exchangeable calcium is discussed.
7. The effect of hydrofluoric acid on the slag residues has been investigated.
8. Experiments with fluorspar slags are described which confirm the view that the phosphate present is fluorapatite of very low solubility in citric acid.