1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-24321-0 SANS 5220:2010Edition 2.2SOUTH AFRICAN NATIONAL STANDARD Water Oxygen absorption Published by SABS Standards Division 1 Dr Lategan
4、 Road Groenkloof Private Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS SANS 5220:2010 Edition 2.2 Table of changes Change No. Date Scope Amdt 1 2005 Amended to change the designation of SABS standards to SANS standards, to update referenced standards and to corr
5、ect the concentration of the potassium permanganate solution. Amdt 2 2010 Amended to update referenced standards. Foreword This South African standard was approved by National Committee SABS SC 147A, Water Water sampling and analysis, in accordance with procedures of the SABS Standards Division, in
6、compliance with annex 3 of the WTO/TBT agreement. This document was published in April 2010. This document supersedes SANS 5220:2005 (edition 2.1). A vertical line in the margin shows where the text has been technically modified by amendment No. 2. SANS 5220:2010 Edition 2.2 1 Water Oxygen absorptio
7、n 1 Scope and field of application This standard specifies a method of determining the oxygen absorption value of water and wastewater. The method is an empirical measure of both organic and inorganic matter that can be oxidized by an acidified permanganate solution over a period of 4 h at 27 C 2 C.
8、 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. Information on currently
9、valid national and international standards can be obtained from the SABS Standards Division. Amdt 1 SANS 111/ISO 835, Laboratory glassware Graduated pipettes. Amdt 1; amdt 2 SANS 112/ISO 648, Laboratory glassware Single volume pipettes. Amdt 1 SANS 115/ISO 385, Laboratory glassware Burettes. Amdt 1;
10、 amdt 2 SANS 128/ISO 1042, Laboratory glassware One-mark volumetric flasks. Amdt 1 SANS 3696/ISO 3696, Water for analytical laboratory use Specification and test methods. 3 Principle The test portion is incubated for 4 h at 27 C 2 C in an acidified permanganate solution. The permanganate is partiall
11、y reduced by the oxidizable material present in the sample. The remainder of the permanganate is titrated with sodium thiosulfate and the oxygen absorption value calculated from the amount of permanganate reduced. The half-reaction for the reduction of permanganate is: MnO4 + 8H+ 5e= Mn2+ 4H2O The r
12、emaining permanganate is titrated with a standard thiosulfate solution: 2MnO4+ 10S2O32+ 16H+= 2Mn2+ 5S4O62+ 8H2O The equivalence point is indicated by the disappearance of the blue starch-iodine complex by reduction of the iodine to iodide with the excess thiosulfate. SANS 5220:2010 Edition 2.2 2 4
13、Reagents NOTE Unless otherwise specified, only use water that complies with the requirements of SANS 3696 and reagents of analytical grade. 4.1 Potassium permanganate solution, c(1/5 KMnO4) = 0,0125 mol/L Amdt 1 Dissolve 4,0 g of potassium permanganate in 1 L of hot water and heat to just under boil
14、ing-point for approximately 2 h. Allow the solution to cool and dilute with water to 10 L. Cover and store overnight in the dark to allow the oxidation of any organic matter and precipitation and settling of manganese dioxide. Carefully decant or siphon off the supernatant or filter through a sinter
15、ed glass funnel or glass wool. Store this solution in a glass stoppered bottle in the dark. 4.2 Potassium dichromate, standard reference solution, c(1/6 K2Cr2O7) = 0,025 mol/L Dissolve 1,226 g of potassium dichromate, previously dried at 105 C 2 C for 2 h and cooled in a desiccator, in water and dil
16、ute to 1 000 mL in a volumetric flask. 4.3 Sodium thiosulfate, stock volumetric solution, c(Na2S2O35H2O) = 0,25 mol/L Dissolve 62 g of sodium thiosulfate pentahydrate in freshly boiled and cooled water. Add 0,1 g of sodium carbonate (Na2CO3) and 10 mg of mercuric iodide (HgI2) and dissolve. Dilute t
17、o 1 000 mL with freshly boiled and cooled water in a volumetric flask. Transfer to an amber stoppered bottle and store in the dark. Allow solution to stand for at least 5 d before use. Discard this solution if it becomes turbid or within three months of the date of preparation. 4.4 Sodium thiosulfat
18、e, standard volumetric solution, c(Na2S2O35H2O) = 0,025 mol/L 4.4.1 Preparation Pipette 100,0 mL of the sodium thiosulfate stock solution (see 4.3) into a 1 000 mL volumetric flask. Add 10 mg of mercuric iodide (HgI2) and dilute to the mark with freshly boiled and cooled water. Standardize this solu
19、tion as described in 4.4.2. 4.4.2 Standardization Dissolve 1 g of potassium iodide (see 4.7) in 70 mL of water in a conical flask and add 10 mL of the sulfuric acid solution (see 4.5). Pipette 20,0 mL of the potassium dichromate solution (see 4.2) into the flask. Mix and allow to stand for 5 min in
20、the dark. SANS 5220:2010 Edition 2.2 3 Titrate with the sodium thiosulfate standard solution (see 4.4.1) until a pale straw colour is obtained. Add 2 mL of the starch solution (see 4.6) and complete the titration to the equivalence point, which is indicated by the disappearance of the blue colour. T
21、he concentration, expressed in moles per litre, of the sodium thiosulfate solution is given by the formula V0,02520,0 = V0,5where 20,0 is the volume of potassium dichromate solution used, in millilitres; 0,025 is the concentration of potassium dichromate, c(1/6 K2Cr2O7), solution, in moles per litre
22、; V is the volume of sodium thiosulfate solution consumed, in millilitres. 4.5 Sulfuric acid solution (25 % (V/V) Slowly add, while stirring, 250 mL of sulfuric acid (d at 25 /25 C = 1,84) to approximately 600 mL of water. Allow to cool and dilute to 1 L. 4.6 Starch solution Add between 0,2 g and 0,
23、3 g of soluble starch to about 5 mL of water and stir. Pour into 100 mL of boiling water and heat until the solution clears. Prepare daily. 4.7 Potassium iodide (KI) 5 Apparatus 5.1 Waterbath, provided with the means for water circulation and capable of maintaining a temperature of 27 C 2 C. 5.2 Gla
24、ssware. Where applicable, only use burettes, pipettes and volumetric flasks that comply with the requirements for class A items as specified in SANS 111, SANS 112, SANS 115 and SANS 128, as relevant. Amdt 1; amdt 2 SANS 5220:2010 Edition 2.2 4 6 Procedure NOTE Unless otherwise specified, only use wa
25、ter that complies with the requirements of SANS 3696. 6.1 Transfer 10 mL of the sulfuric acid solution (see 4.5) and 20,0 mL of the potassium permanganate solution (see 4.1) to a flask of capacity approximately 250 mL. 6.2 Add 100 mL of the sample, or an aliquot diluted to 100 mL, and mix by gentle
26、rotation of the flask. 6.3 Repeat steps 6.1 to 6.2, using 100 mL of water in place of the sample (as a blank). 6.4 Place the flasks in a waterbath that is capable of maintaining the temperature at 27 C 2 C. Place a cover over the waterbath to exclude light, and leave for 4 h. 6.5 Remove the flasks,
27、add 0,5 g of potassium iodide (see 4.7) to each and swirl to dissolve. 6.6 Titrate with the sodium thiosulfate standard volumetric solution (see 4.4) until a pale straw colour is obtained. Add 2 mL of the starch solution (see 4.6) and complete the titration to the equivalence point, which is indicat
28、ed by the disappearance of the blue colour. 7 Expression of results The oxygen absorbed, expressed as O2in mg/L, is given by the formula 50,012)(21cVV where V1 is thevolumeof sodium thiosulfate solution used in blank titration, in millilitres; V2is thevolumeof sodium thiosulfate solution used in sam
29、ple titration, in millilitres; c is the exact concentration, after standardization of the sodium thiosulfate solution, in moles per litre; 0,012 5 is the nominal concentration of the KMnO4solution, in moles per litre. SABS SABS Standards Division The objective of the SABS Standards Division is to de
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