(1) The relationship between phosphate soluble in 2 per cent, citric acid and total phosphate present has been investigated in the following cases:
(a) Phosphates of known composition.
(b) Basic Slags.
(c) Mineral Phosphates.
(2) The relationship is best shown graphically and in nearly all the above cases is a straight line passing through the origin.
For each of three basic slags of widely differing citric solubility, the graphis a straight line showing that citric solubility is a definite constant, independent of the weight taken in the test, when allowance is made for a small constant error in the determination.
(3) The ratio soluble phosphate/total phosphate in the case of the mineral phosphates Gafsa, Ephos, Nauru, and a West Indian phosphate, depends on the weight taken in the test, the graphs are not straight lines.