ISO 4938:2016 pdf free download.Steel and iron Determination of nickel content Gravimetric or titrimetric method
Aciers etfontL’s — Détei,ninution clii nickel — Métliode gruvilnétuique oil titrilnétrique.
7.2.2.2 The following applies to test portions containing more than 5 mg of copper
Follow the procedure as described in 7.2.2.1 but increase the amount of dimethyiglyoxime solution (4.20) for the precipitation. Add 10 ml for each 10 mg of nickel present and add 30 ml in excess.
7.2.2.3 The following applies to test portions containing more than 5 mg of cobalt.
hvaporate the test solution prepared in 7.2.1 or 7.2.2.4 to 100 ml approximately.
Transfer the solution into a 600 ml beaker containing 100 ml of the ammonium citrate buffet’ solution (4.17) and 65 ml of ammonia solution After rinsing the original beaker with water, wash once with 15 ml of ammonia solution (4.13) and add the washing to the test solution.
Add an amount of potassium hexacyanoferi’ate(lIl) solution (4.22) sufficient to oxidize the cobalt and manganese 1)t’esett (6 ml for each 0,1 g of cobalt and manganese) plus 10 % excess. Stir well (the solution should now be red) and, using a jH-meter .52), adjust the solution to pH 8,0 ± 0,2 with ammonia solution (4fl) or acetic acid 4…3). Add 50 i 1 of etha irnl 4L2) and 100 in I of di methylglyox I me solution (4.19) and stir well. Let the solution stand at room temperature for 4 h, checking that the solution remains at ph 8.
Filter through a rapid 12,5 cm hardened paper and wash six to eight times with the cold washing water (4.23).
7.2.2.4 The Following applies to test portions containing cobalt and high concentrations ol copper
To the test portion preparc(1 in 721, add hydrazine dihydrogen sulphate solution (4_21) drop by drop until the chromium is completely reduced.
Remove the copper by electrolysing the solution at controlled potential, commencing the deposition with a cathode potential of —0,15 V (against standard calomel electrode) and gradually reducing to —0,30 V (against standard caloniel electrode). Copper deposition should be complete after about 40 mm when the current remains constant at a very low value.
CompLetion of deposition can be checked by adding about 20 ml of water to the test solution and continuing the electrolysis. 1)eposition is complete if no copper is deposited on the freshly submerged portion of the cathode after 5 mm. Switch off the current to the calomel electrode circuit. Remove the calomel electrode, then remove the platinum electrodes and rinse with water.
Add about 5 ml of nitric acid 14S) and eVaI)orate the solution until copious white fumes are evolved. Cover the heaker with a dry watch-glass and continue heating until the chromium is completely oxidized. Remove the beaker from the heat source and allow to cool. Dilute the solution with 100 ml of water, heat to dissolve the salts and boil for about 5 mm to eliminate chlorine compounds.
Proceed as described in 7.2.23.
7.2.3 Second nickel precipitation
The second nickel precipitation may be omitted for test portions containing less than 20 mg of copper and less than 25 mg of cobalt if the titrimetric determination is to be used, in which case, proceed as described in 7..2S.
Place (lie filter and precipitate obtained in 7.2.2 in the precipitation beaker and cover with a watch glass. Add 15 ml of nitric acid (4.5), 10 ml of sulphuric acid (41) and 4 ml o perchloric acid (4.6), and then heat. Increase the temperature to evaporate the solution until there is a strong emission of white fumes (see Note 1). Cool and dilute with water to about 400 ml.ISO 4938:2016 pdf free download.
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