A new, simple and reliable method has been develoed for metalloyaphic analysis of Nb in high strength steel.
The procedure is as follows:
1. Separation of Nb
a) Dissolve 1 g of sample in 40m
l of HC1 (1:1) at room temperature. Filter and wash with water.
b) Dilute the filterate to 250m
l with water, add 10m
l of phytin solutiol (1%), and boil for 10min, and allow to, stand for 5min. Filter and wash 2 or 3 times with hot water.
c) Return the paper and precipitate to the beaker, add 20m
l of HNO
3, 3m
l of HCIO
4, and 2m
l of H
2SO
4 (1:1), and evaporate to a sirup, and determine Nb as solid solution as described in Section 2 a) to c). d) Transfer the paper and residue (Paragraph a) to the beaker, add 20m
l of HNO
3 (1:1) and 5m
l of H
20
2, and boil for 5min. Filter and wash 2 or 3 times with hot wlter.
e) Add 2m
l of H
2SO
4 (1:1) to the filterate and evaporate to a sirup, and determine Nb as carbonitride as described in Section 2a) to c).
f) Transfer the paper and residue (Paragraph d) to the beaker, add 20m
l of HNOB, S ml of HCI0
4, and 2m
l of H
2SO
4 (1:1), and evaporate to a sirup, and determine Nb as oxide as described in Section 2 a) to c).
2. Photometric determination of Nb
a) Dissolve each of the salt of section 1 c), e) and f) in 20m
l of tartaric acid solution (20%) and 10m
l of HOI (1:1) and dilute to 100m
l in a volumetric flask.
b) Transfer 5m
l portion of solution to 50 ml volumetric flask, add 15m
l of water, and 2m
l of thioglycollic acid solution (10%), mix, allow to stand for 2 min, and then, add 10m
l of HCI (1: 1), 5m
l of EDTA solution (1%), 5m
l of aceton and 2ml of sulfochloro phenol S solution (0.05%).
c) Warm to 60 to 70°C for 5 min, cool, dilute to the mark, and mix. Measure the absorbance against water at 650mμ.
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