This standard specifies the determination of chromium content by ammonium ferrous sulfate volumetric method. This standard is applicable to the determination of chromium content in metallic chromium. Scope of application: chromium content greater than 97.00%. GB/T 4702.1-1997 Chemical analysis method for metallic chromium Determination of chromium content by ammonium ferrous sulfate volumetric method GB/T4702.1-1997 Standard download decompression password: www.bzxz.net

GB/T 4702.1—1997
This standard is equivalent to JIS G1323—1978 "Methods for chemical analysis of metallic chromium - Determination of chromium content by ammonium ferrous sulfate volumetric method". This revision mainly changes the original use of potassium permanganate standard solution back titration to potassium dichromate standard solution back titration for determination of chromium content. This standard replaces GB4702.1—1997 from the date of entry into force. This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is under the jurisdiction of the Information Standardization Research Institute of the Ministry of Metallurgical Industry. This standard was drafted by Hunan Ferroalloy Factory.
The main drafters of this standard are Zhang Yulan, Huang Yan, and Zhao Yiqing. This standard was first issued on October 4, 1984. 174
1 Applicable Figures
National Standard of the People's Republic of ChinabzxZ.net
Methods for chemical analysis of chromium metalThe ammonium ferrous sulfatevolumetric method for the determinationof chromium content
This standard specifies the ammonium ferrous sulfate volumetric method for the determinationof chromium content. This standard is applicable to the determination of chromium content in metallic chromium. Scope of application: Chromium content greater than 97.00%. 2 Method Summary
GB/T 4702. 1—1997
Replaces GB4702.1—84
The sample is decomposed with phosphoric acid. In phosphoric acid and sulfuric acid media, silver nitrate is used as catalyst, chromium is oxidized to hexavalent by ammonium persulfate, chromium is reduced by standard ammonium ferrous sulfate solution, and back titration is performed by standard potassium dichromate solution. 3 Reagents
3.1 Phosphoric acid (p1.69 g/mL).
3.2 Nitric acid (pl.42 g/mL).
3.3 Sulfuric acid (1+1).
3.4 ​​Sulfuric acid (1+4).
3.5 Hydrochloric acid (1+3).
3.6 Silver nitrate solution (5 g/L).
3.7 Manganese sulfate solution Dissolve 100 g of manganese sulfate (MnSO, ​​·5H,O) in water and dilute to 1000 mL. Mix well. 3.8 Potassium permanganate solution (3 g/L).
3.9 Ammonium persulfate solution (200 g/L).
3.10 Sodium diphenylamine tetrasulfonate solution (5 g/L). 3.11 Potassium dichromate standard solution (C(1/6K,Cr2O,)=0.1000mol/L) Weigh 4.904g of standard potassium dichromate dried at 150℃～170℃ for 2h and place it in a 200mL beaker. Dissolve it in a small amount of water and transfer it to a 1000mL volumetric flask. Wash the inner wall of the beaker with water several times. Pour the washing liquid into the volumetric flask and dilute to the scale and mix well. 3.12 Ammonium ferrous sulfate standard solution (0.1 mol/L) Weigh 39.22g of ammonium ferrous sulfate (NH,Fe(SO,)2·6H,O) and dissolve it in 1000mL sulfuric acid (5+95) and mix well. Calibration: Pipette 25.00mL of ammonium ferrous sulfate standard solution into a 300mL beaker, add 25mL of water, 5mL of phosphoric acid (3.1), add 5 drops of sodium diphenylamine tetrasulfonate indicator (3.10), and titrate with potassium dichromate standard solution (3.11) until the solution turns purple-red as the end point. Calculate the liquid density of ammonium ferrous sulfate standard solution according to formula (1): Approved by the State Administration of Technical Supervision on November 11, 1997
Implementation on May 1, 1998
GB/T 4702.1—1997
Concentration of ammonium ferrous sulfate standard solution, tmol/L; Where: C2—
Concentration of potassium dichromate standard solution, mol/L; V,—Volume of potassium dichromate standard solution consumed during titration, mL; V——Volume of ammonium ferrous sulfate standard solution transferred, mL. 4 Sample
The sample should all pass through the 1.68mm sieve.
5 Analysis steps
5.1 Sample quantity
Weigh 0.5000g of sample.
5.2 Blank test
Perform a blank test along with the sample.
5.3 Determination
（1）)
5.3.1 Place the sample (5.1) in a 300mL beaker and cover with a cover glass. Add 20mL phosphoric acid (3.1) and heat to decompose the sample and produce a small amount of white smoke. Cool until the solution still maintains fluidity, then add 20mL sulfuric acid (3.4) and 5mL nitric acid (3.2). Heat until smoke appears to drive away all nitrogen oxides. After cooling, transfer to a 250mL volumetric flask, dilute to the mark with water, mix well, transfer 50.00mL of the solution to a 500mL beaker, add 20mL sulfuric acid (3.3), and dilute to about 200mL with warm water. 5.3.2 Add 0.5 mL potassium permanganate solution (3.8), then add 10 mL silver nitrate solution (3.6) and 20 mL to 25 mL ammonium persulfate solution (3.9), boil to oxidize chromium to dichromic acid and present a reddish color of potassium permanganate, then continue boiling for about 5 min to decompose the excess ammonium persulfate. Add 10 mL hydrochloric acid (3.5) and 5 mL manganese sulfate solution (3.7), boil to completely decompose the permanganate, continue boiling for 2 min to 3 min, cool to room temperature, and add water until the volume of the solution is about 250 mL. 5.3.3 Add ammonium ferrous sulfate standard solution (3.12) to reduce dichromic acid and add 5 mL to 10 mL in excess, add 5 drops of sodium diphenylamine tetrasulfonate indicator (3.10), and immediately titrate with potassium dichromate standard solution (3.11) until the solution just turns purple red. 6 Calculation of analysis results
Calculate the mass percentage of chromium according to formula (2): Cr(%) = V, - V.× K) ×cz × 0. 017 33m. Xr
Wherein: V3-
the volume of ammonium ferrous sulfate standard solution consumed, mL; V-the volume of potassium dichromate standard solution consumed, mL, the ratio of potassium dichromate standard solution to ammonium ferrous sulfate standard solution; K
c2——the concentration of ammonium ferrous sulfate standard solution after calibration, mol/L; m.
the mass of the sample, g;
the ratio of test solution;
0.01733-the mass of chromium equivalent to 1mL of ammonium ferrous sulfate standard solution, g. The analysis results are expressed to two decimal places. 7 Allowable difference
The difference between the analysis results of laboratories should not exceed 0.40%, 176
GB/T5071-1997
This standard is equivalent to the international standard ISO5018:1983 "Determination of true density of refractory materials", and GB/T5071-85 has been revised.
This standard has been revised to modify the following provisions: original 3.7 (change vacuum device)
-original 4.0 (change sampling regulations)
-original 5.1 (rewrite this part)
-original 6.2 (change the number of digits retained in the test results)-original 7 (specify the test error in the form of an appendix) original 8 (change the report content of the test results) This standard replaces GB/T5071-85 "True density test method for refractory materials" from the date of entry into force. Appendix A and Appendix B of this standard are the appendices of the standard. This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Standardization of Refractory Materials. This standard was drafted by the Luoyang Refractory Materials Research Institute of the Ministry of Metallurgical Industry. The main drafters of this standard are Ma Chunhong, Liu Linmei, Zhao Jianli, and Zhang Qing. This standard was first issued in 1955 as YB51-55, revised for the first time in 1963 as YB372-63, revised for the second time in 1975 as YB372-75, and revised for the third time in April 1985 as GB5071-85.
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