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BS EN 62021-2:2007 pdf free

BS EN 62021-2:2007 pdf free.Insulating liquids – Determination of acidity – Part 2: Colourimetric titration.
The test portion is dissolved in a specified solvent and titrated colourimetrically with alcoholic potassium hydroxide to a specified colour using Alkali Blue 6B indicator.
Only reagents of recognized analytical grade and de-ionized water or water of equivalent purity shall be used.
Standard alcoholic solution 005 mol/l potassium hydroxide.
Add 3,0 g of potassium hydroxide to 1 000 ml ± 10 ml of 2-propanol. Boil gently for 10 mm to effect solution. Cool and stopper the flask.
Allow the solution to stand in the dark for 2 days and then filter the supernatant liquid through a 5 im membrane filter. Store in a suitable amber glass bottle.
The concentration of this solution is approximately 005 mol/l and shall be standardized as described in 8.1. For periodic tests on equipment in service, faster titration may be achieved by the use of 0.1 molll potassium hydroxide by agreement between the laboratory and the equipment owner, although this may result in poorer precision and detection limit.
Commercial alcoholic potassium hydroxide solution may be used, if necessary diluting to 0,05 mol/l with 2-propanol. This shall be standardized as described in 8.1.
Store and use In such a manner that the solution is protected from atmospheric carbon dioxide and in such a way that it does not come into contact with cork, rubber or saponifiable stopcock grease. The solution may be protected by inert gas or by means of a guard tube containing soda-lime absorbent.
Titration solvent
2-propanol (isopropanol; IPA), pure.
PotassIum hydrogen phthalate, primary standard This should be dried before use for 2 h at 105 °C.
Standard hydrochloric acid solution
A 0,1 mol/l solution of hydrochloric acid in de-ionized water, prepared as in ISO 6619, may be used. Other acids may be used, provided they are certified against a primary standard.
Alkali blue 6B indicator solution
Dissolve 2 g ± 0.1 g of alkali blue BB in 100 ml of 2-propanol or azeotropic ethanol containing 1 ml of the hydrochloric acid solution. After 24 h, carry out a titration to check whether the indicator has been sufficiently sensitized. The indicator is satisfactory if the colour changes distinctly from blue to red comparable to that of a 10 % solution of cobalt nitrate. If sensitization is insufficient, repeat the addition of the hydrochloric acid solution and check again after 24 h. Continue until sensitization is satisfactory. Filter and store in a brown bottle in the dark.
Commercial alkali blue 68 solution may be used as an alternative if the concentration is within the range 0,05 % to 5 %. If the concentration is not 2 %, the amount added to the solvent in 8.2 and 8.3 should be adjusted to maintain the same ultimate concentration.BS EN 62021-2 pdf download.

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