ISO 4942:2016 pdf download

ISO 4942:2016 pdf download.Steels and irons — Determination of vanadium content — N-BPHA spectrophotometric method
1 Scope
This document specifies an N-benzoylphenylhydroxylamine (N-BPHA) spectrophotometric method for the determination of vanadium in steels and cast irons.
This document is applicable to vanadium contents between 0,005 % and 0,50 % (mass fraction).
2 Normative references
The following documents are referred to in text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical composition
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 Principle
Dissolution of a test portion with appropriate acids.
Addition of orthophosphoric acid to an aliquot of the sample solution to prevent the interference of iron,and addition of potassium permanganate to oxidize vanadium to the pentavalent state.
Selective reduction of excess permanganate by sodium nitrite, in the presence of urea and treatment with N-BPHA and hydrochloric acid to form a complex, followed by extraction of the complex with trichloromethane.Spectrophotometric measurement of the absorbance at approximately 535 nm.
5 Reagents
During analysis, unless otherwise stated, use only reagents of recognized analytical grade and only grade 2 water as specified in ISO 3696 or water of equivalent purity.
8.3 Determination
8.3.1 Preparation of the test solution
Transfer the test portion (8.1) (see 10.1) to a 250 ml beaker, cover with a watch-glass and add 20 ml to 30 ml of the hydrochloric/nitric acids mixture (5.7). When effervescence has ceased, heat gently to complete the dissolution. Add 15 ml to 20 ml of perchloric acid (5.4), raise the temperature so that white perchloric acid fumes appear and reflux in the beaker and continue fuming for about 3 min. NOTE In the case of cast irons, fuming with perchloric acid for about 3 min is not always sufficient to decompose carbides. Total decomposition is only complete when heating is continued until no more fumes are visible in the beaker and crystallization has occurred. After cooling, add about 30 ml of water and 10 ml of perchloric acid (5.4) before continuing as described below from “Add hydrogen peroxide (5.8)…”. Cool, add about 30 ml of hot water and shake to dissolve salts. Add hydrogen peroxide (5.8) dropwise to reduce chromium, gradually heat to boiling and continue for 1 min to 2 min to decompose the excess of hydrogen peroxide. After cooling, filter through a medium texture filter paper and collect the filtrate in a 100 ml one- mark volumetric flask. Wash the filter paper several times with hot water. Dilute to the mark with water and mix.