... pile. Indexes Premium grade First class grade Qualified gradeSodium nitrate(based on dried basis),%≥ 99.7 99.3 98.5 Water ... content,% ≤ 1.0 1.5 2.0 Water insoluble(based on dried basis),%≤ 0.03 0.06 ------ Sodium nitrite ... .01 0.02 0.15 Chloride(based on dried basis),% ≤ 0.25 0.30 ----- Sodium carbonate(based on dried basis),%≤ 0.05 0 ...