GB/T 41711-2022Determination of acid resistance, sulfur resistance and salt resistance of inner coating or laminated-film in metal containers used for food (English PDF)

5.1 Reagents

5.1.1 Water, GB/T 6682, Class III.

5.1.2 Glacial acetic acid.

5.1.3 Citric acid monohydrate (C6H8O7 · H2O): purity > 99 %.

5.1.4 L-cysteine hydrochloride monohydrate (C3H8NO2SCl · H2O): purity > 99 %.

5.1.5 Potassium dihydrogen phosphate (KH2PO4): purity > 99 %.

5.1.6 Disodium hydrogen phosphate dodecahydrate (Na2HPO4 · 12H2O): purity > 99 %.

5.1.7 Sodium sulfide nonahydrate (Na2S · 9H2O): purity > 99 %.

5.1.8 Sodium chloride (NaCl): purity > 99 %.

5.2 Preparation of reagents

5.2.1 Acetic acid solution (3 % volume fraction)

MEASURE 30 mL of glacial acetic acid in a 1000 mL volumetric flask, DILUTE to the mark with water.

5.2.2 Citric acid solution (20 g/L)

WEIGH 21.86 g of citric acid monohydrate (C6H8O7 · H2O), DISSOLVE it in water and DILUTE to 1000 mL.

5.2.3 Mixed solution of L-cysteine hydrochloride (0.56 g/L), potassium dihydrogen phosphate (3.6 g/L), disodium hydrogen phosphate (7.2 g/L)

WEIGH 0.56 g of L-cysteine hydrochloride monohydrate (C3H8NO2SCl · H2O), 3.60 g of potassium dihydrogen phosphate (KH2PO4) and 18.2 g of disodium hydrogen phosphate dodecahydrate (Na2HPO4 · 12H2O), DISSOLVE them in water respectively, MIX them and DILUTE to 1000 mL with water. The mixed solution shall be used within 4 hours after preparation.

5.2.4 Sodium sulfide solution (0.5 g/L)

WEIGH 1.54 g of sodium sulfide nonahydrate (Na2S · 9H2O), DISSOLVE it in water and DILUTE to 1000 mL, ADJUST the pH value to 5.5 ~ 6.0 with lactic acid.

5.2.5 Sodium chloride solution (30 g/L)

WEIGH 30 g of sodium chloride (NaCl), DISSOLVE it in water and DILUTE to 1000 mL. […]