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 40ml of HC1 (1:1) at room temperature. Filter and wash with water.
b) Dilute the filterate to 250ml with water, add 10ml 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 20ml of HNO3, 3ml of HCIO4, and 2ml of H2SO4 (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 20ml of HNO3 (1:1) and 5ml of H202, and boil for 5min. Filter and wash 2 or 3 times with hot wlter.
e) Add 2ml of H2SO4 (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 20ml of HNOB, S ml of HCI04, and 2ml of H2SO4 (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 20ml of tartaric acid solution (20%) and 10ml of HOI (1:1) and dilute to 100ml in a volumetric flask.
b) Transfer 5ml portion of solution to 50 ml volumetric flask, add 15ml of water, and 2ml of thioglycollic acid solution (10%), mix, allow to stand for 2 min, and then, add 10ml of HCI (1: 1), 5ml of EDTA solution (1%), 5ml 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.