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1、INTERNATIONAL STANDARD 2460 INTERNATIONAL DRGANlZATlON FOR STANDARDlZATlON MEXAYHAPOAHAX OPTAHHSAUHX n0 CTAH ,“, * . ,2 i., ;.d. r”si j, _ %, .,ir11 .- . ,. .:.A. , ,. i, ii-=- . _ ,;j;q .;r Lk+ hd= UDC 661.833.623 : 546.72 : 543.42 Ref. No. IS0 2460-1973 (E) Descriptors : sodium carbonates, chemica
2、l analysis, determination of content, iron, photometry. Price based on 2 pages Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/25/2007 22:42:07 MDTNo reproduction or networking permitted
3、 without license from IHS -,-,- FOREWORD IS0 (the international Organization for Standardization) is a worldwide federation of national standards institutes (IS0 Member Bodies). The work of developing International Standards is carried out through IS0 Technical Committees. Every Member Body interest
4、ed in a subject for which a Technical Committee has been set up has the right to be represented on that Committee. International organizations, governmental and nongovernmental, in liaison with ISO, also take part in the work. Draft International Standards adopted by the Technical Committees are cir
5、culated to the Member Bodies for approval before their acceptance as International Standards by the IS0 Council. International Standard IS0 2460 was drawn up by Technical Committee ISO/TC 47, Chemistry, and circulated to the Member Bodies in September 197 1. It has been approved by the Member Bodies
6、 of the following countries : Austria Hungary Belgium India Chile Ireland Czechoslovakia Israel Egypt, Arab Rep. of Italy France Netherlands Germany New Zealand Poland Romania South Africa, Rep. of Switzerland United Kingdom U.S.S.R. No Member Body expressed disapproval of the document. Internationa
7、l Organization for Standardization, 1973 l Printed in Switzerland Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/25/2007 22:42:07 MDTNo reproduction or networking permitted without lice
8、nse from IHS -,-,- INTERNATIONAL STANDARD IS0 2460-1973 (E) Sodium hydrogen carbonate for industrial use - Determination of iron content - 1 ,I 0-phentinthroline photometric method 1 SCOPE This international Standard specifies a l,lO-phenanthroline photometric method for the determination of the iro
9、n content of sodium hydrogen carbonate for industrial use. 2 FIELD OF APPLICATION The method is applicable to products having iron contents equal to or greater than 0,l mg/kg. 3 PRINCIPLE Reduction of the trivalent iron by hydroxylammonium chloride, followed by the formation of a bivalent iron/l, IO
10、-phenanthroline complex in a buffered system. Photometric measurement of the coloured complex at a wavelength of about 510 nm. 4 REAGENTS Distilled water, or water of equivalent purity, shall be used in the test. 4.1 Hydrochloric acid, p approximately 1.19 g/ml, about 38 % (m/m) solution or approxim
11、ately 12 N. 4.2 Ammonia solution, p approximately 0.91 g/ml, about 25 % (m/m) NH, solution or approximately 13 N, with a maximum iron content of 0.2 mg/kg. 4.3 Hydroxylammonium chloride (NH,OH.HCI), 10 g/l solution. 4.4 Buffer solution, pH 4.9. Dissolve 272 g of sodium acetate trihydrate (CH,COONa.3
12、H,O) in about 500 ml of water. Add 240 ml of glacial acetic acid (p approximately 1,05 g/ml, 99 to 100 % (m/m) solution or approximately 17,4 N) to the solution and dilute to 1 000 ml. 4.5 Bromine water, saturated at room temperature. 4.6 l,lO-Phenanthroline hydrochloride monohydrate (C, 2 Ha N,.HCI
13、.H,O), 2,5 g/l solution. This product may be replaced by 1 ,lO-phenanthroline monohydrate (C,H,N,.H,O). 4.7 Iron standard solution, corresponding to 0,200 g of Fe per litre. Dissolve 1,404 3 g of ammonium iron sulphate hexahydrate (NH,),Fe(SO,),.6H,O, weighed to the nearest 0,OOOl g, in 200 ml of wa
14、ter. Add 20 ml of sulphuric acid, p approximately I,84 g/ml, cool to room temperature, dilute to the mark in a 1 000 ml one-mark volumetric flask and mix. 4.8 Iron standard solution, corresponding to 0,010 g of Fe per litre. Transfer 25,0 ml of the iron standard solution (4.7) to a 500 ml one-mark v
15、olumetric flask, dilute to the mark and mix. Prepare this solution immediately before use. 1 ml of this standard solution contains 0,010 mg of Fe. 4.9 Methyl orange, 0.5 g/l solution. 5 APPARATUS Ordinary laboratory apparatus and 5.1 Spectrophotometer, or 5.2 Photoelectric absorptiometer, fitted wit
16、h filters giving maximum transmission between 500 and 520 nm. 6 PROCEDURE 6.1 Test portion Weigh, to the nearest 0.1 g, 100 g of the test sample. 6.2 Blank test Pour 25 ml of water and a volume of the hydrochloric acid solution (4.1) identical to that used to neutralize the test portion (see 6.4.1)
17、into a 600 ml beaker. Add 75 ml of the ammonia solution (4.2). 5 drops of the methyl orange solution (4.9) and then neutralize with the ammonia solution (4.2). Add the hydrochloric acid solution (4.1) drop by drop until the colour changes to red, and then an excess of 2 ml of this acid. Add 5 ml of
18、the bromine water (4.5) to remove the colour of the indicator, boil for 5 min. a Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/25/2007 22:42:07 MDTNo reproduction or networking permitt
19、ed without license from IHS -,-,- is0 2460-1973 6) cool to room temperature, transfer the solution quantitatively to a 250 ml one-mark volumetric flask dilute to the mark and mix. Proceed as described in 6.4.2. 6.3 Preparation of the calibration curve 6.3.1 Preparation of the standard matching solut
20、ions, for photometric measurements with a 5 cm cell. Into a series of five 100 ml one-mark volumetric flasks, transfer the quantities of the iron standard solution (4.8) indicated in the following table : Iron standard solution (4.8) Corresponding mass of Fe I ml w I o* 0 2,5 0,025 5,O 0,050 10.0 0,
21、100 I 15.0 I 0,150 I * Compensation solution. Add to each flask 0,5 ml of the hydrochloric acid solution (4.1) and the amount of water necessary to make up the volume to about 50 ml. Then add 5 ml of the hydroxylammonium chloride solution (4.3). 5 ml of the l,lO-phenanthroline hydrochloride solution
22、 (4.6) and 25 ml of the buffer solution (4.4). Dilute to the mark, mix and wait for 10 min. 6.3.2 Photometric measurements Carry out the photometric measurements with the spectrophotometer (5.1) at a wavelength of about 510 nm, or with the photoelectric absorptiometer (5.2), fitted with suitable fil
23、ters, after having adjusted the instrument to zero absorbance against the compensation solution. 6.3.3 Plotting the calibration curve Prepare a chart having, for example, the iron (Fe) contents in milligrams per 100 ml of standard matching solution as abscissae and the corresponding values of absorb
24、ance as ordinates. 6.4 Determination 6.4.1 Preparation of the test solution Transfer the test portion (6.1) to a 1 000 ml beaker. Add 120 ml of water and neutralize cautiously with the hydrochloric acid solution (4.1) in the presence of 5 drops of the methyl orange solution (4.9). Add an excess of 2
25、 ml of this acid, then 5 ml of the bromine water (4.5). Boil for 5 min, cool to room temperature, transfer quantitatively to a 250 ml one-mark volumetric flask, dilute to the mark and mix. 6.4.2 Colour development Transfer 50,O ml of the test solution (6.4.1) to a 100 ml one-mark volumetric flask. A
26、dd 5 ml of the hydroxylammonium chloride solution (4.3), 5 ml of the l,lO-phenanthroline hydrochloride solution (4.6) and 25 ml of the buffer solution (4.4). Dilute to the mark, mix and wait for 10 min. 6.4.3 Photometric measurement Measure the absorbance of the solution (6.4.2) as described in 6.3.
27、2 after having adjusted the instrument to zero absorbance against the blank test solution (6.2). 7 EXPRESSION OF RESULTS By reference to the calibration curve (6.3). determine the quantity of Fe corresponding to the value of the absorbance measured. The iron content (Fe) is given, in milligrams per
28、kilogram, by the formula 250 1 000 5 OOOml “ X=Xm,= m0 m, is the mass, in grams, of the test portion. ml is the mass, in milligrams, of Fe found in the aliquot portion of the test solution. 8 TEST REPORT The test report shall include the following particulars : a) the reference of the method used; b
29、) the results and the method of expression used; cl any unusual features noted during the determination; d) any operation not included in this International Standard, or regarded as optional. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/25/2007 22:42:07 MDTNo reproduction or networking permitted without license from IHS -,-,-