Add 10 g sodium azide (NaN 3) dissolved in 40 mL distilled water. Alkali-iodide-azide reagent: Dissolve 500 g NaOH or 700 g KOH and 135 g NaI or 150 g KI in distilled water and dilute to 1 litre.Manganous sulphate solution: Dissolve 480 g MnSO 4.4H 2O, 400 g MnSO 2.2H 2O or 364 g MnSO 4.H 2O in distilled water, filter and dilute to 1 litre.Preserve with 1.25 g salicylic acid/litre or by the addition of a few drops of toluene. Dilute to 1 litre, allow to boil for a few minutes and let settle overnight.
Starch indicator: Add cold water suspension of 5 g soluble starch to approximately 800 mL boiling water with stirring.Standardise this with 0.025 N potassium dichromate solution which is prepared by dissolving 1.226 g potassium dichromate in distilled water and diluted to 1 litre. Preserve by adding 5mL chloroform or 0.4 g NaOH/L or 4 g borax and 5 - 10 mg HgI 2/L. Standard sodium thiosulphate 0.025 N: Dissolve 6.205 g sodium thiosulphate (Na 2S 2O 3.5H 2O) in freshly boiled and cooled distilled water and dilute to 1litre.After the iodine has dissolved, dilute to 1 litre and standardise against 0.025 N sodium thiosulphate using starch as indicator. Standard iodine solution 0.025 N: Dissolve 20 - 25 g potassium iodide in a little water and add 3.2 g iodine.Hydrochloric acid: Prepare a 6 N solution.Dissolve 147.9 mg anhydrous Na 2SO 4 in 500 mL distilled water and dilute to 1 litre 1 mL = 100 µg SO 4. Standard sulphate solution: Prepare a standard sulphate solution such that 1 mL = 100 µg SO 4.Barium chloride: Barium chloride crystals.Conditioning reagent: Mix 50 mL glycerol with a solution containing 30 mL concentrated HCl, 300 mL distilled water, 100 mL 95% ethyl or isopropyl alcohol and 75 g NaCl.Standard iron solution: Pipette 50 mL stock solution into 1 litre volumetric flask and dilute to the mark with distilled water.Each 1 mL of this solution contains 200 µg Fe.
Dilute to 1litre with iron free distilled water. Add 0.1 N KMnO4 drop wise until a faint-pink colour persists. Stock iron solution: Add slowly 20 mL concentrated H2SO2 to 50 mL distilled water and dissolve 1.404 g ferrous ammonium sulphate.
1 mL of this reagent is sufficient for no more than 100 µg Fe. Heating is unnecessary if 2 drops of concentrated HCl are added to the distilled water.