BS EN 890-2004 pdf download.Chemical used for treatment of water intended for human consumption — Iron (III) sulfate liquid.
B.3.7 Precision
Under the repeatability conditions the coefficient of variation is 18 % with 10 measurements.
B.4 Determination of free acid
B.4.1 General
This method is applicable to the determination of acidity in iron based coagulants,
The measuring range shall be between a mass fraction of 0,05 % and 10 %.
The limit of determination is a mass fraction of 0.1 %.
B.4.2 Principle
Dilution of a test sample with water. Addition of an excess of sulfuric acid in order to depolymerize the sample.
The depolymerisation is accelerated by heating.
Fluoride ions are added in excess. These form a strong complex with femc ions, and thereby remove their acidic properties, The number of hydrogen ions is determined by titration with sodium hydroxide to pH 9,0 or using phenolphthalein as an indicator.
B.4.3 Interferences
Aluminium and silica interfere with fluoride.
Silicon containing sample gives wrong results.
B.4.4 Reagents
8.4.4.1 Deionised water.
8.4.4.2 Sodium hydroxide solution, c(NaOH) = 0,2 molii.
8.4.4.3 Sulfuric acid solution, c(H2S04) = 0.1 mol/l.
B.4.4.4 Potassium fluoride, KF.2 H20.
B.5.2 Principle
Arsenic (As), antimony (Sb) and selenium (Se) are reduced to the elemental hydrides AsH3, SbH3 and SeH4 by sodium tetrahydroborate. The gaseous hydrides are conveyed with argon gas to a heated quartz cuvette and thermally decomposed. The absorption of the atoms is measured in the light path of an atomic absorption spectrometer at a wavelength specific to the element. The concentrations are calculated by means of calibration curves,
B.5.3 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to the grade 3 in accordance with EN ISO 3696.
8.5.3.1 Hydrochloric acid (HCI), solution, mass fraction 30 %.
B.5.3.2 L-ascorbic acid, solution 100 gil.
8.5.3.3 Oxalic acid, solution 100 gIl.
8.5.3.4 Potassium iodide, solution 100 gil.
B.5.3.5 Sulfuric acid solution, c(H2S04) = 1 molil.
8.5.3.6 Sodium tetrahydroborate solution, mass fraction of 5 % NaBH4 in NaOH solution of a mass fraction of
B.5.3.7 Element stock solutions, (As, Sb, Se) = 1 g/l.
B.5.3.8 Standard element solutions. c1 (As, Sb, Se) = 10 mg/i, to be prepared by dilution of B.5.3.7.
8.5.3.9 Standard element solutions, c2 (As, Sb, Se) = 0,1 mg/I, to be prepared by dilution of B.5.3.8.
8.5.3.10 Element reference solutions, prepared by pipetting 1 ml, 2 ml, 4 ml, 8 ml and 10 ml of each of the standard element solutions (8.5.3.9) into a series of 100 ml volumetric flasks (B.5.4.3), adding 30 ml oxalic acid (B.5.3.3), 10 ml potassium iodide (B.5.3.4), 5 ml L-ascorbic acid (B.5.3.2) and 5 ml hydrochloric acid (B.5.3.1) for As and Sb. Then fill the volumetric flasks up to the mark with water. The concentrations of the reference solutions will be 1 pg/i, 2 pg/I. 4 pg/I, 8 pg/i and 10 pg/I.
B.5.3.11 Sample blank solution.
B.5.4 Apparatus
B.5.5 Procedure
B.5.5.1 Spectrometer settings
The atomic absorption spectrometer (8.5.4.4) and the hydride generator unit (B.5.4.6) are adjusted in accordance with the operating manual issued by the manufacturer. The spectrometer is operating at the wavelength for each element:
— As:193,7nm;
— Sb:217,6nm;
— Se:196,Onm.
The quartz cuvette is heated to 900 C.
B.5.5.2 Measurement of arsenic and antimony
Take 20 ml of the sample solution (5,2.3.1.5) with a pipette (8.5.4.1) and transfer to a 100 ml volumetric flask (8.5.4.3). Add with a graduated cylinder (B.5.4.2) 30 ml oxalic acid (B.5.3.3), 10 ml potassium iodide (B.5.3.4). 5 ml ascorbic acid (B.5.3.2) and 5 ml hydrochloric acid (B.5.3.1), then make up to the mark with water, The prepared solution shall be allowed to stand for 3 h to ensure complete reaction. Then transfer 5 ml of the solution with a pipette (B.5.4.1) to the reduction vessel, add 10 ml sulfuric acid (B.5.3.5) and start the hydride control unit. The solution is reduced with NaBH4 and immediately AsH3 and SbH3 are transferred with the argon gas (8.5.4.7) to the 900 °C heated quartz cuvette. Measure the absorption of arsenic with an arsenic specific lamp (B.5.4.5) at wavelength 193,7 nm. Measure the absorption of antimony with an antimony specific lamp (B.5.4.5) at wavelength 217.6 nm.
8.5.5.3 Measurement of selenium
Transfer 20 ml of the sample solution (5.2.3.1.5) with a pipette (B.5.4.1) to a 100 ml volumetric flask. Add 30 ml oxalic acid (B.5.3.3) and 5 ml hydrochloric acid (8.5.3.1), then make up to the mark with water. Transfer 5 ml of the solution with a pipette to the reduction vessel, add 10 ml sulfuric acid (B.5.3.5) and start the hydride control unit. The solution is reduced with NaBH4 and immediately SeH4 is transferred with the argon gas (B.5.4.7) to the 900 °C heated quartz cuvette. Measure the absorption of selenium with a selenium specific lamp (B.5.4.5) at wavelength 196,0 nm.
B.5.5.4 Calculation and expression of results
The As, Sb and Se concentrations Ce in the sample solution expressed In micrograms per litre are read out from the calibration function or regression function:BS EN 890-2004 pdf download.