... 68.0% min. (2) Inactive phosphate, as P2O5: 7.5% max. (3) PH of 1% water solution: 5.8-7.3 ... : Qualified (5) Water insoluble: 0.05% max. (6) Iron, as Fe: 0.05% max. Usage: Used in industries of oil fields ... .0% min. (2) Inactive phosphate, as P2O5: 7.5% max. (3) PH of 1% water solution: 5.8-6.5 ... ) Heavy metal, as Pb: 0.001% max. (9) Iron, as Fe: 0.05% max.Usage: Mainly used as additive agent,PH adjusting ...