GB/T 4702.13-1987 Chemical analysis method for chromium metal - Oscillographic polarographic method for determination of lead content GB/T4702.13-1987 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods far che mlcal analy sis ofchromium metal
The usiciloplarographle method For thedetermnination of lead contentLILX: 669.26
:543.253.06
GB 4702.13-87
This standard is applicable to the determination of lead content in metallic chromium, with a determination range of 0.0003~0,0015%. This standard complies with GB146778 "General Principles and General Provisions for Chemical Analysis Methods for Metallurgical Products". 1 Method Summary
The sample is decomposed with hydrochloric acid, chromium and other coexisting elements are complexed with ammonium citrate, lead is extracted with copper reagent chloroform in an ammonia medium, phosphoric acid is used as the base liquid, the peak height of lead at -0.45V is measured on an oscillographic polarograph, and the analysis results are calculated by the standard comparison method.
2 Reagents
The water used for analysis is double distilled water.
2.1 Ascorbic acid (solid)
2.2 Hydrochloric acid (1+2), high-grade purity.
2.3 Nitric acid (pl.42g/ml)
2.4 Nitric acid (1+1):
2.5 Perchloric acid (p1. 68g/ml)
2.6 Ammonium citrate solution (50%)
2.7 Copper reagent (sodium diethyldithiocarbamate) solution (0.5%)2.8 Ammonium hydroxide (p0.90g/ml)
2.9 Phosphoric acid: Transfer 27.20ml phosphoric acid (e1.70g/ml) into a 1000ml volumetric flask: dilute to the mark with water and mix well. 2.10 Trifluoromethane (p1.48g/ml).
2.11 Lead standard solution
2.11.1 Weigh 0.2000g of metallic lead (purity 9.99%, pre-wash the oxide film with nitric acid (1-9), then wash with water and anhydrous alcohol, and air-dry) and place it in a 200ml beaker, add 20ml of nitric acid (2.4), and dissolve it in warm water. After cooling, transfer it to a 1000ml volumetric flask, dilute it to the mark with water, and mix it. This solution contains 200ug lead in 1ml. 2.11.2 Transfer 50.00ml of lead standard solution (2.11.1) to a 1000ml volumetric flask, add 20ml of nitric acid (2.4), dilute it to the mark with water, and mix it. 1 ml of this solution contains 10ug of lead. 2.11.3 Pipette 50.00 ml of the lead standard solution (2.11.2) into a 500 ml volumetric flask, add 10 ml of nitric acid (2.4), dilute to the mark with water, and mix. 1 ml of this solution contains 1 scale of lead. 3 Instruments
Oscillographic polarograph: use the dropping mercury electrode as the working electrode, the saturated calomel electrode as the reference electrode, and the platinum electrode as the auxiliary electrode. Ministry of Metallurgical Industry: Approved on March 3, 1987
Implemented on March 1, 1988
4 Sample
The sample should all pass through a 1.68 mm sieve.
5 Analysis steps
5.1 Sample quantity
Weigh 1.0000 g of sample.
5.2 Blank test
Carry out a blank test with the sample.
5.3 Determination
GB 4702.13--87
5.8.1 Place the sample (5.1) in a 150md beaker, cover with blood, add 20ml hydrochloric acid (2.2), heat on a low-temperature electric hot plate until the sample is completely dissolved, continue heating for 3~5min, add 20ml ammonium citrate solution (2.6) at the fever, and mix. Continue heating for 2~3min, remove, cool: add 10ml ammonium hydroxide (2.8), mix 5.3.2 Transfer the solution to a 125ml separatory funnel, wash the beaker with 10~15ml of water, and place it in the separatory funnel. Add 5ml copper reagent solution (2.7), mix.
5.3.3 Add 10ml trichloroethane (2.10), shake 2mm, let stand to separate, and transfer the organic orange to a 50ml beaker. Add 1 ml of tricyanomethane (2.10) to the aqueous phase, shake for 1 minute, let stand for stratification, and combine the organic phases. Add 2 ml of tricyanomethane (2.10) to the aqueous phase, do not shake, let stand for 1 minute, and combine the organic phases. 5.3.4 Add 2 ml of nitric acid (2.3) to the beaker containing the organic phase, and volatilize the organic matter on a low-temperature electric heating plate, then move the beaker to a high temperature to carbonize the remaining organic matter, remove it, and cool it. Add 2 ml of nitric acid (2.3) and 10 g of perfluoric acid (2.5). Cover with a table dish, heat until the carbonized matter is completely cyanided (the solution becomes clear), and remove the table blood. Continue heating until the perfluoric acid white smoke is gone, remove it, and cool it. 5.3.5 Add 20,00 ml of phosphoric acid (2.9) and mix well. Add 0.1 g of ascorbic acid (2.1) and mix well. Pass nitrogen for more than 3 minutes, and measure the peak height of lead at -0.45 V and the peak height of blank elution at a starting potential of -0.20 V on an oscillographic polarograph under cathode polarization and conventional conditions.
5.4 Preparation of lead standard comparison solution and measurement of lead peak height Take three portions of lead standard solution (2.11) with a lead content similar to that in the sample (5.1), add lead-free metal in an amount corresponding to that in the sample (5.1) respectively, and carry out the following steps according to 5.3.1 to 5.3.5. 6 Calculation of analysis results
Calculate the percentage of lead according to the following formula:
Pb %)=4
Where.h!—
-×100
Height of lead peak in lead standard comparison solution after subtracting blank, format: height of lead peak in test solution after subtracting blank, format: ho
Amount of lead in lead standard comparison solution
mo—maximum of sample, g. wwW.bzxz.Net
7 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference listed in the following table. Additional Notes:
GB 4702.13—87
2), 0003 ~ 0. 0010
>0. 00 10 ~0. 0015
This standard was drafted by Hunan Ferroalloy Factory. From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB582—6 "Methods for Chemical Analysis of Metallic Chromium" will be invalidated. The level of this standard is marked GB4702.13-81.
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