Volumetric Standards for Standardization

Cerium (IV) sulfate solution 0.1 mol/l (0.1 N) (Catalog No. 109092)

• Reaction type: Redox titration/cerimetry
• Kind of titration: Direct titration
• Volumetric standard:
  Iron(II) ethylenediammonium sulfate (Catalog No. 102402).
  Arsenic (III) oxide should not be used as volumetric standard because of the high toxicity and the difficult handling.
  Atmospheric oxygen soxidizes the alkaline solution of As2O3 very easily.
• Method of initial introduction: Direct weighing

Indication

1. Visual: with ferroin indicator solution (Catalog No. 109161); color change from orange to faint blue
2. Potentiometrical: with platinum single rod measuring chain and automatic titrator.

Analytical procedure

Approx. 700–750 mg of iron (II) ethylenediammonium sulfate (Volumetric Standard), dried for 24 h over silica gel, are exactly weighed into a titration vessel of approx. 150–200 ml, dissolved in 50 ml of sulfuric acid 0.5 ml/l and titrated to the color change with the cerium (IV) sulfate solution 0.1 mol/l to be tested.

Calculation

di-Sodium EDTA Solution 0.1 mol/l (Catalog No.108431)

• Reaction type: Complexation
• Kind of titration: Direct titration
• Volumetric standard: Zinc metal (Catalog No.102409)
• Method of initial introduction: Division into aliquots by gravimetry

Indication

1. visual: indicator buffer tablet (Catalog No. 108430); color change from red to green (mixed color),
2. potentiometrical: ion selective copper electrode with reference electrode and automatic titrator using 1 ml of copper EDTA solution 0.1 mol/l per determination instead of the indicator buffer tablet.

Analytical procedure

1. Preparation of a zinc chloride solution 0.1 mol/l volumetric standard: Approx. 6.54 g of zinc (Volumetric Standard) are analy tically exactly weighed, transferred to an exactly weighed 1-l volumetric flask and dissolved in approx. 70 ml of hydrochloric acid 25 % GR for analysis overnight. The volumetric flask is then made up to approx. 1 l and the total weight is determined to the second decimal.

   Calculation of the mass fraction w (Zn) introduced in mg/g solution:

   

   Cf = correction factor, calculated from the effective content of the volumetric standard acc. to the certificate divided by 100.

   * via back-titration with copper nitrate solution 0.1 mol/l
2. Titration:
   In a titration vessel of about 150–200 ml, approx. 19 g of zinc chloride volumetric standard solution are analytically exactly weighed per difference weighing using a plastic syringe. The solution is diluted to approx. 100 ml with water GR for analysis, one indicator buffer tablet and 10 ml of ammonia solution 25 % GR for analysis are added and the solution is titrated with the Na2EDTA solution to be tested.
   Calculation
   
   t = titer
   w (Zn) = mass of zinc in 1 g of zinc chloride volumetric standard solution
   f = stoichiometric factor (volumetric equivalent in mg/ml)

Standard solutions which can be tested with the standardized Na2EDTA solution:

• Barium chloride solution 0.05 mol/l*
• Barium perchlorate solution 0.05 mol/l*
• Copper nitrate solution 0.1 mol/l
• Copper sulfate solution 0.1 mol/l
• Mercury(II) nitrate solution 0.05 mol/l
• Zinc chloride solution 0.1 mol/

Hydrochloric acid 0.1 mol/l (0.1N)(Catalog No. 109060)

• Reaction type: Acid-base titration/acidimetry
• Kind of titration: Direct titration
• Volumetric standard: Tris(hydroxymethyl)-aminomethane (TRIS)
• Method of initial introduction: Division into aliquots by gravimetry

Indication

1. Visual: mixed indicator 4.5 acc. to Mortimer; color change from blue to red (mixed color).
2. Potentiometrical: pH electrode like e.g. single-rod measuring chain and automatic titrator.

Analytical Procedure

1. Preparation of a tris(hydroxymethyl)aminomethane solution 0.1 mol/l (0.1 N) (Volumetric Standard solution):
   Approx. 12.114 g of tris(hydroxymethyl)aminomethane (volumetric Standard), stored for 24 h over a neutral drying agent in a desiccator and exactly weighed, are transferred to a dry, weighed 1-l volumetric flask, dissolved in water GR for analysis and made up to approx. 1 l. The total weight is determined to two decimals.
   Calculation of the mass fraction w (TRIS) in mg/g solution:
   
   Cf = correction factor, calculated from the effective content of the volumetric standard acc. to the certificate divided by 100.
2. Titration:
   Approx. 19 g of tris(hydroxymethyl)aminomethane solution (Volumetric Standard solution) are weighed exactly into a beaker or titration vessel of approx. 150–200 ml using difference weighing of a plastic syringe, diluted to approx. 100 ml with water GR for analysis and titrated to the color change with hydrochloric acid 0.1 mol/l to be tested.
   Calculation
   
   t = titer
   w (TRIS) = mass of TRIS in 1 g of volumetric standard solution
   f = stoichiometric factor (volumetric equivalent in mg/ml).

Standard solutions which can be checked with the standardized hydrochloric acid 0.1 mol/l:

All strong and weak bases in the concentration range of 0.01 to 0.25 mol/l considering the choice of the suitable indicator resp. the pH range. For the titration of the content of the total alkali of strong bases it is recommended to use methyl orange with an end point in the pH range of approx. 4.5. The exact determination of the carbonate content requires a boiling just before the end of the titration, as described in the analytical procedure. Here the mixed indicator 4.5 acc. to Mortimer is recommended. For the determination of the hydroxide only, methyl red with a transition range of pH 4–6 or, better, phenolphthalein with a transition range of pH 8–10 can be utilized. For the titration of weak bases, the use of indicators with a transition range of between pH 4 and 6 is recommended. For specific ranges mixes indicators are available like, e.g. mixed indicator 5 for ammonia titrations.

Hydrochloric acid 1 mol/l (1 N)(Catalog No. 109057)

• Reaction type: Acid-base titration/acidimetry
• Kind of titration: Direct titration
• Volumetric standard: Tris(hydroxymethyl)aminomethane (TRIS) (Catalog No. 102408)
• Method of initial introduction: Direct weighing

Indication

1. Visual: mixed indicator 4.5 acc. to Mortimer (Catalog No. 101359); color change from blue to red (mixed color).
2. Potentiometrical: pH electrode like single-rod measuring chain and automatic titrator.

Analytical procedure

Approx. 2.3 g of tris(hydroxymethyl)aminomethane (Volumetic Standard), stored for 24 h over a neutral drying agent in a desiccator,are exactly weighed in a 150 ml beaker or titration vessel and dissolved in approx. 100 ml of water GR for analysis. The solution is titrated to the color change resp. the end point with hydrochloric acid 1 mol/l to be tested

Calculation

t = titer
m = mass of TRIS
f = stoichiometric factor (volumetric equivalent in mg/ml)
Cf = correction factor, calculated from the effective content of the volumetric standard acc. to the certificate divided by 100.

Important standard solutions which can be checked with the standardized hydrochloric acid 1 mol/l:

All strong and weak bases in the concentration range of 0.5 to 2 mol/l considering the choice of the suitable indicator resp. the pH range. For the titration of the content of the total alkali of strong bases it is recommended to use the mixed indicator 4.5 acc. to Mortimer or methyl orange with a pH transition point of abt. 4.5. For the determination of the hydroxide portion of the base, methyl red with a transition range of pH 5–6 or phenolphtalein with a pH transition range of 8–10 can also be used. For the titration of weak bases, the use of indicators with a transition range of between pH 4 and 6 is recommended. Here mixed indicators are available for specific ranges like e.g. mixed indicator 5 for ammonia titrations.

Iodine Solution 0.05 mol/l (0.1 N) (Catalog No. 109099)

• Reaction type: Redox titration/iodometry
• Kind of titration: Direct titration
• Volumetric standard:
  Sodium thiosulfate solution 0.1 mol/l (Catalog No. 109147) (standardized with the initial burette),
  Arsenic (III) oxide should not be used as volumetric standard because of the high toxicity and the difficult
  handling. Atmospheric oxyen oxidizes the alkaline solution of As₂O₃ very easily.
• Method of initial introduction: Using the measurement of volume(under consideration of the temperature)

Indication

1. Visual: with starch solution 1 %; color change from colorless to blue
2. Potentiometrical: with platinum single rod measuring chain and automatic titrator.

Analytical Procedure

In a titration vessel of about 150–200 ml exactly 19.00 ml of sodium thiosulfate solution 0.1 mol/l (standardization see 5.4.4.2) are transferred from the initial burette, diluted to approx. 100 ml with water GR for analysis and titrated to the end point with the iodine solution to be tested.

Calculation

Standard solution which can be checked with the standardized iodine solution

• Sodium arsenite solution 0.05 mol/l.

Further applications: Determination of sulfur dioxide, arsenium compounds.

Perchloric acid 0.1 mol/l in anhydrous acetic acid (Catalog No. 109065)

• Reaction type: Acid-base titration in non-aqueous medium
• Kind of titration: Direct titration
• Volumetric standard:
  Tris(hydroxymethyl)aminomethane (TRIS) (Catalog No. 102408).
  Alternative: Potassium hydrogen phthalate using the same analytical procedure. Tris(hydroxymethyl)aminomethane does not require drying, avoids the precipitation of potassium perchlorate and shows identical results when used for the potentiometric titration.
• Method of initial introduction: Direct weighting

Indication

1. Visual: with Oracet blue 2R (Catalog No. 101487); color change from pink to blue, with 1-naphtholbenzein (Catalog No. 106202); color change from yellow to green.If for the following application of perchloric acid a different indicator is used, this indicator must also be utilized for the calibration.
2. Potentiometrical: pH electrode.

Analytical procedure

Approx. 220–230 mg of tris(hydroxymethyl)aminomethane (Volumetric Standard), stored for 24 h over silica gel, are exactly weighed into a titration vessel of approx. 150–200 ml, dissolved in 80 ml of acetic acid anhydrous GR for analysis and titrated to the color change with the perchloric acid 0.1 mol/l to be tested.

Calculation

Potassium permanganate solution 0.02 mol/l (0.1 N) (Catalog No. 109122)

• Reaction type: Redox titration/manganometry
• Kind of titration: Direct titration
• Volumetric standard: Sodium oxalate (Catalog No. 102407)
• Method of initial introduction: Division into aliquots by gravimetry

Indication

1. Visual: without indicator using the intrinsic color; first visible pink coloration.
2. Potentiometrical: with platinum single-rod measuring chain and automatic titrator.

Analytical Procedure

1. Preparation of a sodium oxalate solution 0.05 mol/l (Volumetric Standard solution):
   Approx. 6.70 g of sodium oxalate (Volumetric Standard), dried at 110 °C to constant weight, are exactly weighed and transferred to a weighed 1-l volumetric flask, dissolved in water GR for analysis and made up to 1 l. The total weight is determined to two decimals.
   Calculation of the mass fraction w (sodium oxalate) in mg/g solution:
   
   Cf = correction factor, calculated from the effective content of the volumetric standard acc. to the certificate divided by 100.
2. Titration: Approx. 19 g of sodium oxalate solution (Volumetric Standard) are weighed exactly into a beaker or titration vessel of 300 ml, using the difference weighing of a plastic syringe. To this solution 10 ml of sulfuric acid 96 % (attention: heating!)and approx. 170 ml of water GR for analysis, warmed to 80–85 °C, are added and the solution is titrated at this temperature with the potassium permanganate solution 0.02 mol/l to be tested under permanent stirring until the color change. The pink coloration appearing immediately must disappear after the addition of a few ml of the titrant. The decolorized solution is titrated carefully and slowly until again a noticeable faint pink coloration appears.
   
   Calculation
   
   
   t = titer
   w (sodium oxalate) = mass of sodium oxalate in 1 g of volu metric standard solution
   f = stoichiometric factor (volumetric equivalent in mg/ml).

Standard solution which can be checked with the standardized potassium permanganate solution

• Oxalic acid solution 0.05 mol/l.

Silver nitrate solution 0.1 mol/l (0.1 N) (Catalog No. 109081)

• Reaction type: Precipitation titration/argentometry
• Kind of titration: Direct titration
• Volumetric standard: Sodium chloride (Catalog No. 102406)
• Method of initial introduction: Division into aliquots by gravimetry

Indication

1. Potentiometrical: combined silver electrode and automatic titrator.
2. Visually possible with potassium chromate (Catalog No. 104952): color change from yellow to red-brown; this indication is only possible after change of the analytical procedure corresponding to the determination acc. to Mohr in neutral solution.

Changes in connection with the visual indication:

• closeable titration vessel (Erlenmeyer flask),
• Barium perchlorate solution 0.05 mol/l*
• no nitric acid present,
• the titration vessel must be shaken vigorously after each addition of the titrant.

Analytical procedure

1. Preparation of a sodium chloride solution approx. 0.1 mol/l (Volumetric Standard solution) (Catalog No. 102406)
   Approx. 5.85 g of sodium chloride (Volumetric Standard), dried at 150 °C to constant weight, are exactly weighed and transferred to a weighed 1-l volumetric flask, dissolved in water GR for analysis and made up to 1 l. The total weight is determined to two decimals.
   Calculation of the mass fraction w (NaCl) in mg/g solution:
   
   Cf = correction factor, calculated from the effective content of the volumetric standard acc. to the certificate divided by 100.
2. Titration: Approx. 19 g of sodium chloride solution (Volumetric Standard) are weighed exactly into a titration vessel of 150–200 ml (e.g. beaker), using the difference weighing of a plastic syringe, and diluted to approx. 100 ml with water GR for analysis, 5 ml of nitric acid 25 % are added and the solution is titrated with the silver nitrate solution to be tested with vigorous stirring.

Calculation

t = titer
w (NaCl) = mass of NaCl in 1 g of volumetric standard solution
f = stoichiometric factor (volumetric equivalent in mg/ml).

Sodium Thiosulfate Solution 0.1 mol/l (0.1 N) (Catalog No. 109147)

• Reaction type: Redox titration/iodometry
• Kind of titration: Back-titration based on substitution
• Volumetric standard:Potassium iodate should be preferred to the toxic potassium di chromate which is suspected to be carcinogenic.
• Method of initial introduction: Division into aliquots by gravimetry

Indication

1. Visual: with starch solution 1 %; color change from blue to colorless
2. Potentiometrical: with platinum single rod measuring chain and automatic titrator.

Analytical procedure

1. Preparation of a potassium iodate solution 1/60 mol/l (0.1 N) (Catalog No. 102404)
   Approx. 3.57 g of potassium iodate (Volumetric Standard), dried for 2 h at 130 °C, are exactly weighed, transferred to a 1-l volumetric fl ask, dissolved in water GR for analysis and made up to 1 l with water. The total weight is determined to the second decimal.
   Calculation of the mass fraction w (KIO3) in mg/g solution:
   
   
   Cf = correction factor, calculated from the effective content of the volumetric standard acc. to the certificate divided by 100.
2. Titration:
   In a titration vessel of about 300 ml, approx. 19 g of potassium iodate volumetric standard solution are analytically exactly weighed per difference weighing using a plastic syringe. 150 ml of water GR for analysis, 3 g of potassium iodide and 5 ml of hydrochloric acid 25 % are added and the iodine liberated is titrated immediately with the sodium thiosulfate solution to be tested.
   Calculation
   
   

   t = titer
   w (KIO₃) = masse KIO₃ in 1 g volumetric standard solution
   f = stoichiometric factor (volumetric equivalent in mg/ml)

Standard solutions which can be checked with the standardized sodium thiosulfate solution:

• Bromate solution 1/60 mol/l
• Bromide-bromate solution 0.05 mol/l
• Iodide-iodate solution 1/64 mol/l
• Iodine solution 0.05 mol/l
• Potassium dichromate solution 1/60 mol/l
• Potassium iodate solution 1/60 mol/l
• Potassium permanganate solution 0.02 mol/l (for use in iodometry

Sodium hydroxide solution 0.1 mol/l (0.1 N) (Catalog No. 109141)

Determination of the NaOH content

• Reaction type: Acid-base titration/alkalimetry
• Kind of titration: Direct titration
• Volumetric standard: Potassium hydrogen phthalate
• Method of initial introduction: Direct weighing

Indication

1. visual: with phenolphthalein (Catalog No. 107227); color change from colorless to faint pink
2. potentiometrical: pH electrode like e.g. single rod measuring chain and automatic titrator

Analytical Procedure

Approx. 380 mg of potassium hydrogen phthalate (Volumetric Standard), dried at 120 °C to constant weight, are exactly weighed into a titration vessel of approx. 200 ml, dissolved in approx. 100 ml of water GR for analysis and titrated to the color change with sodium hydroxide solution 0.1 mol/l to be tested.

Calculation

Determination of the total content of alkali (hydroxide and carbonate)

• Reaction type: Acid-base titration/acidimetry
• Kind of titration: Direct titration
• Volumetric standard: Volumetric standard: Hydrochloric acid 0.1 mol/l tested against tris (hydroxymethyl)aminomethane (Volumetric Standard)(Catalog No. 109060)
• Method of initial introduction: Volumetric using the burette provided for the sodium hydroxide solution

Indication

1. Visual: with mixed indicator 4.5 acc. to Mortimer (Catalog No. 101359); color change from blue to red (mixed color)
2. Potentiometrical: pH electrode like e.g. single rod measuring chain and automatic titrator.

Analytical Procedure

Exactly 19.00 ml of sodium hydroxide solution to be tested, using a burette provided for the base, are initially introduced into a titration vessel of approx. 200 ml, diluted with approx. 80 ml of water GR for analysis and titrated to the color change with hydrochloric acid 0.1 mol/l just tested.For bases with an increased carbonate content – recognizable by the delayed color change – or for a very exact determination,it is recommended to boil the solution in order to remove the carbon dioxide dissolved after the addition of approx. 18.5 ml of hydrochloric acid.

Calculation

Sodium hydroxide solution 1 mol/l (1 N) (Catalog No. 109137)

Determination of the NaOH content

• Reaction type: Acid-base titration/alkalimetry
• Kind of titration: Direct titration
• Volumetric standard: Potassium hydrogen phthalate (Catalog No. 102400)
• Method of initial introduction: Direct weighing

Indication

1. Visual: with phenolphthalein (Catalog No. 107227); color change from colorless to faint pink
2. Potentiometrical: pH electrode like e.g. single rod measuring chain and automatic titrator.

Analytical Procedure

Approx. 3,800 mg of potassium hydrogen phthalate (Volumetric Standard), dried at 120 °C to constant weight, are exactly weighed into a titration vessel of approx. 200 ml, dissolved in approx. 100 ml of water GR for analysis and titrated to the color change with sodium hydroxide solution 1 mol/l to be tested.

Calculation

Determination of the total content of alkali (hydroxide and carbonate content)

• Reaction type: Acid-base titration/acidimetry
• Kind of titration: Direct titration
• Volumetric standard: Hydrochloric acid 0.1 mol/l (Catalog No. 109057) tested against tris (hydroxymethyl) aminomethane (Volumetric Standard) (Catalog No. 102408)
• Method of initial introduction: Volumetric using the burette provided for the sodium hydroxide

Indication

1. Visual: with mixed indicator 4.5 acc. to Mortimer (Catalog No.101359); color change from blue to red (mixed color)
2. Potentiometrical: pH electrode like e.g. single rod measuring chain and automatic titrator.

Analytical Procedure

Exactly 19.00 ml of sodium hydroxide solution to be tested are initially introduced into a titration vessel of approx. 200 ml using a burette provided for the base, diluted with approx. 80 ml of water GR for analysis and titrated to the color change with hydrochloric acid 0.1 mol/l just tested. For bases with an increased carbonate content – recognizable by the delayed color change – or for a very exact determination,it is recommended to boil the solution in order to remove the carbon dioxide dissolved after the addition of approx. 18.5 ml of hydrochloric acid.

Calculation