BS EN 973-2002 pdf download.Chemicals used for treatment of water intended for human consumption — Sodium chloride for regeneration of ion exchangers.
B.3.2 Principle
Ferrocyanide (hexacyanoferrate (II)] and iron (II) form in acid solution, the iron(ll) hexacyanoferrate (II) complex
which, in presence of iron(lll) oxidizes immediately to iron (Ill) hexacyanoferrate Fe4[Fe(CN)6J3 Prussian Blue. The absorbance of this complex is measured at a wavelength around 700 nm.
The Prussian Blue can be filtered on a membrane filter. After redissolution with potassium hydroxide, the Prussian Blue is reformed in a greatly reduced volume.
B.3.3 Reagents
All reagents shall be of recognized analytical grade and the water used shall conform to grade 3 in accordance with
EN ISO 3696.
B.3.3.1 Sodium chloride, hexacyanoferrate-free.
8.3.3.2 Sulfuric acid solution, c(HSO4) 0,5 moUl.
B.3.3.3 Potassium hydroxide solution, c(KOH) 0,05 mol!l.
B.3.3.4 Fe(ll) – Fe(lll) solution
Add 200 g of ammonium iron (II) sulfate L(NH4)2S04. FeSO4. 6H20j and 259 of ammonium iron (Ill) suLfate [(NH4)2S04. Fe2(S04)3 24H20J into a 1 000 ml volumetric flask. Dissolve with water, add 100 ml of sulfuric acid solution (8.3.3.2), dilute to the mark and mix.
Filter the solution and store in a dark bottle.
8.3.3.5 Potassium hexacyanoferrate (II), stock standard solution (I), c(K4[Fe(CN)6). 3H20) = 1,000 gIl,
Transfer 1.000 g of potassium hexacyanoferrate (II) K4(Fe(CN)6J 3H20 to a 1000 ml volumetric flask. Dissolve with water, add 5 ml of potassium hydroxide solution (B.3.3.3), dilute to the mark and mix.
Store in a dark bottle for a maximum of one month.
8.3.3.6 Potassium hexacyanoferrate (II), standard solution (II), c(K4(Fe(CN)6J. 3H20) = 50,0 mgIl.
Transfer 50,0 ml of the stock solution (I) (B.3.3.5) and 5 ml of potassium hydroxide solution (8.3.3.3) to a 1 000 ml volumetric flask. Dilute to the mark and mix.
Prepare this solution just before use.
B.3.4 Apparatus
Ordinary laboratory apparatus and glassware together with the following.
B3.4.1 Spectrometer or,
B.3.4.2 Photocolorimeter, fitted with a fitter ensuring maximum transmission between 690 nm and 710 nm.
NOTE The type of apparatus used (spectrometer or photocolorimeter), the path length and the wavelength (or type of filter) should be specified.
B.3.4.3 Membrane fitter about 50 mm diameter, 0,3 pm maximum porosity.
B.3.5 Procedure
B.3.5.1 Test portion
Weigh, to the nearest 0,1 g, about 100 g (m) of the laboratory sample.
B.3.5.2 Test solution
Transfer the test portion (B.3.5.1) and water to a 500 ml volumetric flask. Dilute to the mark and mix.
B.3.5.3 Blank test solution
Prepare a solution containing 100 g of sodium chloride (B.3.3.1) per litre.
B.3.5.4 Calibration
B.3.5.4.1 Calibration solutions
Transfer 10,09 of sodium chloride (6.3.3.1) and the volumes of standaro souuon jil) Lb..JO) given in tne Table B,8 to a series of 100 ml one-mark volumetric flasks. Dilute to about 50 ml with water and add 10 ml of potassium hydroxide solution (B.3.3.3).
B.3.5.4.3 Spectrometric measurements
Adjust the apparatus to zero absorbance against water.
Carry out the spectrometric measurements using a spectrometer (B.3.4. 1) set up at the maximum of absorbance (wavelength around 700 nm) or a photocolorimeter (8.3.4.2) fitted with the appropriate filter in cells of 4 cm to 5 cm optical path length.
B.3.5.4.4 Calibration curve
Subtract the absorbance of the zero calibration solution from that of each of the other calibration solutions and plot a graph showing the quantities of potassium ferrocyanide, in micrograms. on the abscissa and the corresponding absorbances on the ordinate.
8.3.5.5 Determination
8.3.5. 5.1 Direct method
Transfer 50,0 ml of the blank test solution (8.3.5.2) or of the blank test solution (8.3.5.3) to a 100 ml one-mark
volumetric flask and continue as described in B.3.5.4.2.
B.3.5.5.2 Filtration method
Transfer the 500 ml of test solution (B.3.5.2) or of the blank test solution (8.3.5,3) to a 600 ml beaker,
Add, mixing after each addition, 10 ml of sulfuric acid solution (B.3.3.2) and 25 ml of Fe(ll)- Fe(lll) solution (B.3.3.4). Allow to stand for 15 mm.
Filter under vacuum through a membrane filter (8.3.4.3) and wash twice with 15 ml of water (pH <7).
Transfer the filter into a beaker containing 10 ml of the potassium hydroxide solution (8.3.3.3) and dissoLve the precipitate.
Transfer the solution to a 100 ml one-mark volumetric flask, add 10.09 of sodium chloride (B.3.3.1), dilute to 60 ml, mix and continue as described In B.3.5.4.2.
8.3.5.5.3 Spectrometnc measurements
Carry out the spectron,etnc measurements of the two solutions obtained in B.3.5.5.1 or 8.3.5.5.2 according to the instructions given in B.3.5.4.3.
NOTE I Hexacyanoferrate (II) is determined simultaneously with hexacyanoferrate (Ill).BS EN 973-2002 pdf download.