Prepare 0.05 mol/l Iodine Solution

General Information:

    One liter of this solution contains 12.690 g of iodine (I, atomic weight: 126.90).

Procedure:
    Weigh about 14 g iodine, dissolve in 100 ml of potassium iodide solution and add 3 drops of hydrochloric acid and water to make 1,000 ml. Store in a bottle with a ground-glass stopper, and restandardize frequently.
 

Standardization:  

    Weigh accurately about 0.15 g of arsenic trioxide (standard reagent), previously powdered and dried at 100ˆ to constant weight, and dissolve it in 20 ml of 1 mol/l sodium  hydroxide by heating if necessary. Add about 40 ml of water and 2 drops of  methyl orange TS, and add diluted hydrochloric acid (1 ˠ 4) until the yellow color of the solution changes to light pink. Add 2 g of sodium hydrogen carbonate, about 50 ml of water, and 3 ml of
starch TS, and titrate with 0.05 mol/l iodine until a blue color persists.

  1 ml of 0.05 mol/l Iodine = 4.946 mg As2O3

Prepare Molar Solution of Hydrochloric Acid

General Information:

One liter of this solution contains 36.461 g of hydrochloric acid (HCl).

 Procedure:
    Measure 95 ml of hydrochloric acid, and add water to make 1,000 ml.

Standardization: 

  Weigh accurately about 1.5 g of sodium carbonate (standard reagent), previously dried at about 270ˆ for 1 hour, dissolve it in 100 ml of water, and titrate with 1 mol/l hydrochloric acid (indicator: 2 drops of bromophenol blue TS). Near the end point, boil to expel carbon dioxide, and immediately continue the titration.

  1 ml of 1 mol/l hydrochloric acid = 52.99 mg of Na2CO3

0.5 mol/l Hydrochloric Acid
    Prepare and standardize as directed under 1 mol/l Hydrochloric Acid, using
47.5 ml of Hydrochloric Acid.

0.2 mol/l Hydrochloric Acid
    Dilute 1 mol/l hydrochloric acid with water to 5 times its original volume, or
prepare as directed under 1 mol/l Hydrochloric Acid, using 19 ml of hydrochloric
acid. Standardize as directed under 1 mol/l Hydrochloric Acid.

0.1 mol/l Hydrochloric Acid
    Dilute 1 mol/l hydrochloric acid with water to 10 times its original volume, or
prepare as directed under 1 mol/l Hydrochloric Acid, using 9.5 ml of hydrochloric
acid. Standardize as directed under 1 mol/l Hydrochloric Acid.

0.02 mol/l Hydrochloric Acid
    Dilute 0.1 mol/l hydrochloric acid with water to 5 times its original volume,
and standardize as directed under 1 mol/l Hydrochloric Acid.

0.01 mol/l Hydrochloric Acid
    Dilute 0.1 mol/l hydrochloric acid with water to 10 times its original volume,
and standardize as directed under 1 mol/l Hydrochloric Acid.

Prepare 0.1 mol/l Ferrous Ammonium Sulfate Solution

General Information:

One liter of this solution contains 39.214 g of ferrous ammonium sulfate (Fe(NH4)2(SO4)2ŋ6H2O, molecular weight: 392.14).

Procedure:
    Weigh 40 g of ferrous ammonium sulfate, dissolve in 100 ml of cooled, diluted sulfuric acid and add water to make 1,000 ml.
 

Standardization:  

    Measure exactly 25 ml of 0.1 mol/l ferrous ammonium sulfate, and titrate with 0.1 mol/l ceric sulfate (indicator: 2 drops of o-phenanthroline TS) until the red color of the solution changes to light blue.

Prepare 0.1 mol/l Ferric Ammonium Sulfate Solution

General Information:

       One liter of this solution contains 48.22 g of ferric ammonium sulfate (Fe(NH4) (SO4)ŋ12H2O, molecular weight: 482.19).

Procedure:
      Weigh 49 g of ferric ammonium sulfate, dissolve in cooled mixture of ̒ml of sulfuric acid and  300 ml of water, and add water to make 1,000 ml.
 

Standardization: 

       Measure exactly 25 ml of 0.1 mol/l ferric ammonium sulfate into an iodine-flask, add 5 ml of hydrochloric acid and shake. Add and dissolve 2 g of potassium iodide, stopper tightly, and allow to stand for 10 minutes. Add 50 ml of water, titrate liberated iodine with 0.1 mol/l sodium thiosulfate. When the color of the solution changes to light yellow near the end point, add 3 ml of starch TS as the indicator, and continue the titration until the blue color of the solution disappears. Perform a blank test in the same manner, and make any necessary correction. Store, protecting from light, and restandardize frequently.

Prepare 0.05 mol/l EDTA Solution

General Information:

      One liter of this solution contains 18.612 g of disodium
ethylenediaminetetraacetate (C10H14N2Na2O8ŋ2H2O, molecular weight: 372.24).

Procedure:
     Weigh 18.7 g of disodium ethylenediaminetetraacetate, and dissolve in
freshly boiled and cooled water to make 1,000 ml.

Standardization:   

     Measure exactly 20 ml of 0.05 mol/l EDTA, add 2 ml of ammoniaʵammonium chloride buffer (pH 10.7) and water to make about 100 ml, and titrate with 0.025 mol/l zinc chloride (indicator: 5 drops of eriochrome black T TS).

                                       Volume (ml) of 0.025 mol/l zinc chloride consumed
   Normality factor =   ----------------------------------------------------
                                                 Volume (ml) of 0.05 mol/l EDTA ʷ 2

Prepare 0.1 mol/l Ceric Sulfate Solution

General Information:

    One liter of this solution contains 33.224 g of ceric sulfate (Ce(SO4)2,
    molecular weight: 332.24).

Procedure:
    Weigh 55 g of ceric ammonium sulfate, transfer into a beaker, mix with 31 ml of sulfuric acid, and add carefully a few 20-ml portions of water to dissolve the mixture. Cover the beaker, allow to stand overnight, filter through a glass filter, and add water to make 1,000 ml.
 

Standardization: 

 Weigh accurately about 0.2 g of arsenic trioxide (standard reagent), previously dried at 100ˆ for 1 hour, add 25 ml of sodium hydroxide solution (2 ˠ 25), and dissolve while shaking. Add 100 ml of water, 10 ml of diluted sulfuric acid (1 ˠ 3), 2 drops of o-phenanthroline TS, and 2 drops of a solution of osmic acid in 0.05 mol/l sulfuric acid (1 ˠ 400), and titrate with 0.1
mol/l ceric sulfate until the red color of the solution changes to light blue.

                                                      Weight (g) of arsenic trioxide * 1,000 
   Normality factor =  ___________________________________________
                                            Volume (ml) of 0.1 mol/l ceric sulfate consumed * 4.946

Prepare 0.1 mol/l Ceric Ammonium Sulfate

General Information:

    One liter of this solution contains 66.858 g of ceric ammonium sulfate (Ce(SO4)2ŋ2(NH4)2SO4ŋ4H2O, molecular weight: 668.58). 

Procedure:
    Weigh 67 g of ceric ammonium sulfate, and dissolve in 0.5 mol/l sulfuric acid
to make 1,000 ml. Standardize before use.

Standardization:   

     Measure exactly 25 ml of 0.1 mol/l ceric ammonium sulfate, add 20 ml of water and 20 ml   

     of diluted sulfuric acid (1 ˠ 20), dissolve 1 g of potassium iodide, and titrate immediately   

     with 0.1 mol/l sodium thiosulfate. When the color of the solution changes to light yellow  

     near the end point, add 3 ml of starch TS as the indicator, and continue the titration until  

     the blue color of the solution disappears. Perform the  blank test, and make any necessary  

     correction.