GB/T 8570.7-1988 Determination of iron content in liquid anhydrous ammonia - o-phenanthroline spectrophotometric method GB/T8570.7-1988 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Liquid anhydrous ammonia
Determination of iron content-o-phenanthrolintspectrophotometric method
UDC 661,518
GH8570.7-88
This standard refers to the international standard 1S06685-82 "1 Industrial chemical products-General method for determination of iron content-1.10-Phenanthrolin spectrophotometric method".
This standard specifies the o-phenanthrolin spectrophotometric determination method for iron content in liquid anhydrous ammonia (liquid ammonia). 1 Reference Standards
GB3049 Method for determination of iron content in chemical products, o-phenanthroline spectrophotometric method GB603 Method for preparation of chemical reagents and products GB8570.1 Sampling of liquid ammonia laboratory samples GB 8570.3 Determination of the content of anhydrous nitrogen residues by sub-quantitative method 2 Principle
After evaporating the liquid ammonia sample at room temperature, use hydrochloric acid to dissolve the iron in the evaporation residue, and use ascorbic acid to reduce the valence iron to monovalent iron. At pH 2-9: the valence iron and o-phenanthroline form an orange-red complex, and the H absorbance is measured at a wavelength of 510nm. 3 Reagents and Solutions
In the analysis, unless otherwise specified, only analytical reagents, distilled water or water of equivalent purity can be used. 3.1 Refrigerant solid - mixture of carbon monoxide (+ ice) and industrial alcohol, refrigeration temperature -35 to -40℃: 3.2 Sulfuric acid (GB 625-77); 3.3 Sulfuric acid (GH625-77): about 10% (m/m) solution; 3.4 Hydrochloric acid (GB622-77): about 10% (m/m) solution; 3.5 Ammonia water (GB631-77): about 2.5% (m/m) liquid; 3.6 Glacial acid (GH 676-78) 3.7 Sodium sulfate (GB 693-77); 3.8 Acetic acid-sodium acetate slow-induction solution: PH 4.5, prepared according to GB63. 3.9 Ascorbic acid: 2% (m/m) solution, expiration date 10 days 3.10 Oxyphenacyl sulfate (GB1293-77): 0.2% (m/m) solution, store in dark place, colorless solution for use: 3.11 Ammonium ferric sulfate [NH4Fc(SO+)2*12H4O) (GB 1279-77); 3.12 Iron standard solution: 1 ml contains 0.10) mg iron. Weigh 0.863 g of ammonium ferric sulfate (3.11), weigh to 0.001 K, place in a 200 ml beaker, add 100 ml water, 10 ml sulfuric acid (3.2), transfer all to a 1000 ml volumetric flask after dissolution, dilute with water to scale, shake well; 3.13 Standard solution of iron: 1 ml contains 0.010 mg iron. Take 50.0ml of standard iron solution (3.12) and put it into a 500ml volumetric flask, dilute it to the mark with water and shake it well. Preparation of the solution: Approved by the Ministry of Chemical Industry of the People's Republic of China on December 2, 1987 and implemented on September 1, 1988; GB 8570.7-88 3.14 Benzophenone red (HG3-958-76): 1g/L 95% (V/V) ethyl alcohol solution; 3.15 Silicone grease: For lubricating glass. 4 Instruments: Usual experimental instruments and: 4.1 Sample assembly: Assemble the instrument according to the provisions of 14.1 of GR8570.3 and its diagram. 4.2 Spectrophotometer: Equipped with a 3cm thick glass colorimetric diaphragm. 5 Sampling
Take the test sample according to GB8570.1. 6 Operating procedures
6.1 Sample collectionWww.bzxZ.net
Weigh the mass of two conical flasks A and B, each filled with about 500ml sulfuric acid solution (3.3) and 2 drops of methyl red solution (3.14), and connected with a connecting tube from the white connection point 5, and weigh to 0.1g. Immerse the stoppered test tube in the coolant (3.1) in the flask to a depth of one-fourth, and connect a cone to A and B. The following operations are carried out according to GB8570.3416.1 starting from "rotate the piston 3, make the test tube closed, 12 ends..." to collect the sample.
6.2 Determination
6.2.1 Drawing of standard curve
6.2.1.1 Preparation of standard colorimetric solution
As indicated in the table below, add the given volumes of iron standard solution (3.13) into a series of 100 ml volumetric flasks: Capacitor No.
Iron standard solution (3.13)
Corresponding content
Add about 60 ml of water to each volumetric flask, use hydrochloric acid solution (3.4) or nitrogen water (3.5) to determine the pH value of the solution (check with precision pH test paper), add 2.5 ml ascorbic acid solution (3.9) and 11 ml buffer solution (3.8), then add 5 ml of o-phenazone solution (3.10) to each volumetric flask No. 2 to No. 6 for color development. Each of the above-mentioned volumetric bottles is diluted to the scale with water, and the absorbance of each color standard colorimetric solution is measured. 6.2.1.2 Determination of the spectrophotometric solution
Use the standard colorimetric solution without the addition of o-filament solution as a reference, adjust the absorbance of the spectrophotometer (4.2) to zero at a wavelength of 510nm, and measure the absorbance of each color standard colorimetric solution. 6.2.1.8 Drawing a standard curve
Use the micrograms of iron contained in 10ml of the standard colorimetric solution as the horizontal axis and the corresponding absorbance as the vertical axis to draw a standard curve: 6.2.2 Preparation and determination of test solution
GB 8570-7-88
6.2.2.1 Preparation of test solution
Take out the test tube containing the sample from the test tube stand. Let the ammonia slowly diffuse through the two ends at room temperature until the bottom of the test tube is ammonia water, and the other evaporation residues composed of non-selective substances overflow at room temperature. Add 3 ml of acid solution (3.4) to the test tube to make the aqueous solution of the evaporation residue acidic, then transfer all of it into a 100 ml volumetric flask, dilute with water to the mark, refer to the regulations in the manual, transfer an equal amount of the above solution into two 100 ml volumetric flasks, add 1.00 ml of iron standard solution (3.13) to one of the volumetric flasks, add about 60 ml of water to each, and adjust the pH to close to 2 with saline solution (3.4) and ammonia water (3.5) (check with precision pH test paper), then add 2.5 ml of ascorbic acid solution (3.9) and 10 ml of buffer solution (3.8) to each, then add 5 ml of calcium phosphate (3.10) to the volume of the iron standard solution (3.13). Both volumetric flasks are diluted with water to the mark and add a spoon. 6.2.2.2 Determination of absorbance
Use the test solution to which the o-phenanthene solution has not been added for color development as a reference. At a wavelength of 510 nm, measure the absorbance of the color development test solution by measuring the absorbance of the spectrophotometer (4.2) and obtain the result. Find the iron content corresponding to the absorbance of the color development test solution from the standard line (6.2.1.3) and subtract the number of micrograms of iron (10 g) equivalent to 1.01 ml of the standard solution (3.13). This is the approximate iron content of the test solution. The iron content X expressed in milligrams per gram (mg/kg) is calculated according to the following formula: X=
Where: ms·Sample mass is the number of milliliters of liquid ammonia collected in the test tube multiplied by 0.68 (0.68g/ml is the density of liquid ammonia) and the sum of the mass increments of the connection from the 5th connecting point of the attached white tube, %; mi—the iron content measured in the color test solution, μg; d-the sum of the volume of the test solution and the recorded value of the subsampled test solution used for color development. The arithmetic mean of the parallel determination results is taken as the determination result. Additional remarks:
This standard was prepared by the Shanghai Chemical Research Institute of the Ministry of Chemistry. The Shanghai Chemical Research Institute of the Ministry of Chemistry and Lingjing Chemical Industry were responsible for the drafting of this standard. The main drafters of this standard are Hui Shuikang, Jin Zhigen, Yao Yaosheng, Liu Miaode and Zhang Wenwei.
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