| Release of zinc and phosphate ions from glasses has been studied in
aqueous medium (pH-5.7, 6.5 and 8.0). Zinc phosphate glasses of
five different compositions corresponding to ZoO: P20 5 molar ratio
1.1, 1.3, 1.4, 1.7 and 2.0 were used. Keeping particle size constant for
all glasses, leaching time, temperature and pH were chosen as variables.
Chemical analyses of the glasses showed an appreciable
amount of water in the glass compositions which varied with the
mole ratio of glass modifier to glass former (soaking time at the
melting temperature ~emaining constant). The release of zinc during
48 hours from different mole ratio compositions of glasses under
study has been found to be in the order of 150-420 lgfml, 20-310
lg/ml and 100-380 lg/ml at pH 5.7, 6.5 and 8.0 respectively.
The results of the above study clearly indicated that the release of
ZnO and P20 5 from such glasses can be controlled for agricultural
use only by taking care of the ratio of ZoO: P20 5 and P20s: H20
in the glass composition. The field trial results in sample Sa (ZnO:
P20 5-1.4) are quite promising and are presented in the paper. |
