Division 4 REAGENTS United Kingdom Original text. Later amendments are not shown. 4.1Sodium carbonate-bicarbonate buffer solution. 4.2Buffer substate. 4.3Division 4.3 4.3.1Zinc sulphate solution. 4.3.2Potassium hexacyanoferrate (II) solution. ← Division 3 Division 4 Division 4.1 →