Abstract
Since water and phosphoric acid content seem to be important conditions in manufacturing "serpentine superphosphate", their effects on the conversion to available magnesium in the reaction between superphosphate and serpentine were studied. Sixteen-mesh commercial superphosphate (Table 1,a) was mixed with 100-mesh serpentine (Table 1,b) in the 3 : 1,4 : 1,6 : 1,and 8 : 1 proportions; and water was added to these four mixtures to 15% content, respectively (Table 2), or three phosphoric acid solutions were added to 4 : 1 mixtures, respectively (Table 2). Total, 2% citric acid soluble, and water soluble magnesias were determined after 1,7,14,and 21 days curings at 29℃, while being compared with the change of pH value. From results obtained, the effects of water and free phosphoric acid were discussed, referring to the chemical reaction (cf. Equation : 1〜5). It was concluded that water and free phosphoric acid are important factors of the conversion to available magnesium, and the presence of about 15% water and several per cent free phosphoric acid increases largely both amount and speed of this conversion.
