BS ISO 18632:2010 pdf free download Alloyed steel — Determination of manganese — Potentiometric and visual titration method
This International Standard specifies a potentiometric or visual titration method for the determination of themass fraction of manganese in alloyed steels. The method is applicable to mass fractions of manganesebetween 2 % and 25 %.Vanadium and cerium interfere with the measurement. lf the mass fraction of ceriumin the sample is less than 0,01 %,or the mass fraction of vanadium in the sample is less than 0,005 %, theinterference is negligible. lf the mass fraction of cerium in the sample is greater than 0,01%,or the massfraction of vanadium in the sample is greater than 0,005 %, a theoretical correction is necessary.
2Normative references
The following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies. Forundated references,the latest edition of the referenceddocument (including any amendments) applies.
ISO 648,Laboratory glassware — Single-volume pipettesISO 1042,Laboratory glassware – One-mark volumetric flasks
ISo 3696, Water for analytical laboratory use – Specification and test methods
ISO 4942, Steel and iron- Determination of vanadium content—N-BPHA spectrophotometric methodISO 4947:1986, Steel and cast iron—Determination of vanadium content— Potentiometric titration methodISO 9647:1989,Steel and iron – Determination of vanadium content – Flame atomic absorptionspectrometric method
ISO14284:1996,Steel and iron — Sampling and preparation of samples for the determination of chemicalcomposition
3Principle
Dissolution of a test portion in appropriate acids.Addition of phosphoric acid.Oxidation of manganese tomanganese(Il) in phosphoric acid medium with ammonium nitrate. Visual titration of manganese(Il) withferroammoniumdisulfate standard solution with N-phenylanthranilic acid as the indicator. Alternatively,potentiometric titration with ferroammoniumdisulfate standard solution. If the sample contains vanadium andcerium, the mass fraction of manganese shall be corrected.
4Reagents
During the analysis, use only reagents of recognized analytical grade and only grade 2 water as specified inlso 3696.
4.1Ammonium nitrate,NH4NOa.
4.2 Urea.
4.3 Phosphoric acid, ρ approximately 1 ,69 g/ml.
4.4 Nitric acid, ρ approximately 1 ,42 g/ml.
4.5 Hydrochloric acid, ρ approximately 1 ,1 9 g/ml.
4.6 Sulfuric acid, diluted 1+3.
4.7 Sulfuric acid, diluted 5+95.
4.8 N-phenylanthranilic acid solution, C 6 H 5 NHC 6 H 4 COOH, approximately 2 g/l.
Dissolve 0,20 g of N-phenylanthranilic acid and 0,20 g of sodium carbonate in 100 ml of water and filter.
4.9 Potassium dichromate solution, 0,002 50 mol/l.
Weigh 0,735 5 g of high-purity potassium dichromate which shall be previously dried at 150 °C for at least 2 hand cooled in a desiccator. Put the weighed mass in a 250 ml beaker and dissolve it in water. Transfer thesolution quantitatively into a 1 000 ml one-mark volumetric flask, dilute to the mark with water and mix.
4.10 Manganese standard solution, corresponding to 1,00 g of Mn per litre.
Weigh, to the nearest 0,1 mg,1,000 g of pure manganese metal [purity W 99,9 %(mass fraction)]. Place it in a250 ml beaker and add 40 ml of hydrochloric acid(4.5). Cover with a watch glass and heat gently untilcomplete dissolution.Cool and transfer the solution quantitatively to a 1 000 ml one-mark volumetric ‘flask,dilute to the mark with water and mix.1 ml of this standard solution contains 1,00 mg of Mn.
4.11 Ferroammoniumdisulfate solution,standard volumetric solution,0,015 mol/1.
4.11.1 Preparation of the solution.
Dissolve 5,9 g of ferroammoniumdisulfate [(NHa)Fe(SO4)2-6H20] in 1 000 ml of sulfuric acid (4.7) and mix.4.11.2 Standardization of the solution (to be carried out just before use).
4.11.2.1Visual titration method.
4.11.2.1.1 Titration.
Transfer three portions of 20,00 ml of the potassium dichromate solution (4.9) to three 250 ml conical flasks.Add 20 ml of sulfuric acid (4.6), 5 ml of phosphoric acid (4.3).Add water up to a volume of approximately150 ml.Proceed as specified in 7.2.2.1.
Calculate the mean of the three values of the ferroammoniumdisulfate solution volume,V. The differencebetween the values should not exceed 0,05 ml.
4.11.2.1.2Correction for N-phenylanthranilic acid.
Transfer three portions of 5,00 ml of the potassium dichromate solution (4.9) to three 250 ml conical flasks.Add 20 ml of sulfuric acid (4.6) and 5 ml of phosphoric acid(4.3). Titrate the solution with theferroammoniumdisulfate solution’(4.11.1) untilthe end point is approached ‘. Add 2 drops ofN-phenylanthranilic acid solution (4.8), continue the titration until disappearance of the purplish red color and