GB/T 15072.19-1994 Methods for chemical analysis of precious metals and their alloys Determination of chromium content in gold alloys GB/T15072.19-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Chemical analysis methods for precious metals and their alloys
Determination of chromium content in gold alloys
Gold alloys--Determination of chromium content1 Subject content and scope of application
This standard specifies the method for determining the chromium content in gold alloys. GB/T 15072.79--94
This standard is applicable to the determination of chromium content in AuNiCr5-1 and AuNiCr5-2 alloys, with a determination range of 0.5%3This standard is not used as an arbitration analysis method.
2 Reference standards
GB1.4 Standardization guidelines for chemical analysis of the standard GB1467 General principles and general provisions for chemical analysis methods of metallurgical products 3 Method summary
The sample is dissolved in mixed acid, sulfurous acid is used to reduce and separate the gold, and silver nitrate is used as a catalyst in a sulfuric acid and phosphorus mixed acid medium. Chromium (II) is oxidized to hexavalent by magnetic persulfate, sodium diphenylamine sulfonate is used as an indicator, and chromium (V) is titrated with ammonium ferrous sulfate standard titration solution 4 Reagents
Hydrochloric acid (pl.19g/mL).
4.2 Nitric acid (pl.42g/mL)
4.3 Hydrochloric acid 1+100).
Mixed acid: Mix 3 units of hydrochloric acid (4.1) with 1 unit of sulphuric acid (4.2). Prepare it before use. Sodium fluoride solution (50g/1.).
Sulphurous acid (in terms of SO. Content not less than 6%) 4.7
Sulphuric acid and phosphorus acid mixture: add 300ml phosphoric acid (pl.70g/ml) and 500ml sulfuric acid (ol.84g/ml) to 200ml water, stir and mix 4.8
Silver nitrate solution (10g/L). wwW.bzxz.Net
4.9 Ammonium persulfate solution (250g/L).
4.10 Chromium standard solution. Weigh 0.5658g of standard potassium dichromate (pre-dried at 150C for 1h and cooled to room temperature in a desiccator), place in a 100ml beaker, dissolve in water, transfer to a 1000ml volumetric flask, and dilute to scale with water. Mix well, and 1ml of this solution contains 0.2mg chromium.
4.11 Standard titration solution of ammonium ferrous sulfate c(Fe3:）=0.010 mol/1,) 4.11.1 Preparation: Weigh 3.92g ammonium ferrous sulfate FeS0,·(NH4),S):·6H.O). Dissolve in 100ml sulfuric acid (1-1), dilute to 1L with water, and mix.
4.11.2 Calibration and calibration of indicator: Add 10ml sulfuric acid to each of 6 300ml beakers. Heat to evaporate and smoke. Approved by the State Administration of Technical Supervision on 1994-05~11 124
Implementation on 1994-12-01
GB/T 15072.19-94
Cool, add 150ml. water, add 5.00ml. and 10.00ml of potassium dichromate standard solution respectively, three portions each. Add 3 drops of sodium lysinesulfonate indicator, titrate with ammonium ferrous sulfate standard titration solution until the solution changes from rose red to bright green as the end point, : average calibration The extreme value of the volume of ammonium ferrous sulfate standard titration solution consumed should not exceed 0.2ml., average value. Calculate the calibration value of the indicator according to formula (1):
V Va— 2V,
Wherein: V, the calibration value of the 3 drops of indicator added during titration, m[.Vl:. The volume of the standard ammonium ferrous sulfate titration solution consumed in titrating 5ml of the standard chromium solution, ml.; V
The volume of the standard ammonium ferrous sulfate titration solution consumed in titrating 10ml of the standard chromium solution, mlc Calculate the actual concentration of the standard ammonium ferrous sulfate titration solution according to formula (2): VXc
(V + V) X 0. 0173 32
Wherein:
-actual concentration of standard ammonium ferrous sulfate titration solution, mol/L; -volume of standard chromium solution taken during titration, mL; V.---
C.concentration of standard chromium solution.g/mL
V.volume of standard ammonium ferrous sulfate titration solution consumed in titrating chromium during calibration, mL.V. -—correction value of 3 drops of indicator, mlL.; (2)
0.017332mass of chromium in grams equivalent to 1.00mL standard ammonium ferrous sulfate titration solution (cFeSO·(NH4)2SO.·6Hz0)—1.000mol/L).
4.12sodium diphenylamine sulfonate solution (2g/1.). 5Test sample
Process the sample into scraps. Remove oil stains with two ketones if necessary. Wash and dry. Mix well. 6 Analysis steps
6.1 Test sample
Weigh the sample according to Table 1, accurate to 0.0001g. Table 1
Chromium content, %
>1. 0~3.0
Carry out two independent determinations and take the average value, 6.2 Determination
Test sample cover, g
6.2.1 Place the test sample (6.1) in a 150ml beaker, add 10mL of mixed acid (4.4), cover the surface with blood, and heat until the test sample is completely dissolved. 6.2.2 Add 5ml of sodium chloride solution and evaporate at low temperature until it is almost dry. Add 5mL hydrochloric acid (4.1) and evaporate to near dryness, repeat three times. 6.2.3 Add 30mL water, heat to dissolve the residue, add 15mL sulfuric acid, keep it slightly boiling for 30min, remove it, cool it, 6.2.4 filter it with medium-speed filter paper, and collect the filtrate in a 300mL beaker. Wash the beaker and precipitate with hydrochloric acid (4.3) 7~8 times each. 6.2.5 Add 5mL nitric acid and 10mL sulfuric acid mixed acid (4.7). Heat until it smokes for 2min, and cool it. Rinse the surface blood and the wall of the cup with water, add 120mL water, 1mL silver nitrate solution, 10mL ammonium persulfate solution, and boil it for 5min. Cool it slightly, add 10mL sodium chloride solution, and continue to boil until the red color disappears (there is no red color when the sample does not contain manganese). Cool the solution to room temperature with running water. 6.2.6 Add 3 drops of sodium diphenylamine sulfonate solution. Titrate with standard ammonium ferrous sulfate titration solution until the solution changes from rose red to bright green 125
color, which is the end point.
Explanation of analysis results
Calculate the percentage of chromium according to formula (3):
GB/T 15072.19-94
(Vs + Vo) X c X 0. 017 332
Cr(%) =
× 100
Wherein: V.-The volume of standard ammonium ferrous sulfate titration solution consumed by the chromium in the titration test solution, ml.; V. —·3 drops of indicator correction value, mL; actual concentration of ammonium ferrous sulfate standard titration solution, mol/L; (3)
and 1.00ml ammonium ferrous sulfate standard titration solution (c[FeSO,·(NH,),SO,·6H01-1.000mol/L.0. 017 332———
Equivalent mass of chromium in grams;
Mass of the test sample.
Analysis results are expressed to two decimal places.
Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference listed in Table 2. Table 2
Chromium content
0.50~1.00
≥1.00~3.00
Additional notes:
This standard was proposed by China Nonferrous Metals Industry Corporation. This standard was drafted by Kunming Nonferrous Metals Research Institute. This standard was drafted by the 621st Institute of the Ministry of Aerospace Industry. The main drafters of this standard are Jiang Xiuyu and Huang Shumao. 126
Allowable difference
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