Page 100 - 20250602 EEA QM Edition 6.0

Quality Requirements Edition 6.0 European Enamel Association

8.2.1.3 Determination of bivalent iron, sulphuric acid pickling 8.2.1.4 Determination of nickel sulphate, nickel-exchange bath

Purpose and scope Purpose and scope

Too high a content of iron (II)-sulphate can lead to a crystallizing pickling bath while In order to guarantee an even nickel deposition, the concentration of nickel
cooling down. The concentration of iron in pickling baths has to be checked sulphate is to be kept constant.
regularly.
Analysis instructions:
Analysis instructions
25 ml of a cooled (20 C) sample of the nickel bath is to be diluted with about 100 ml
0
5 ml of a cooled (20 C) sample of the pickling bath solution is to be mixed with distilled water in an Erlenmeyer flask. After about 20 ml ammonium chloride solution
0
about 100 ml distilled water and 10 ml Reinhardt-Zimmermann-solution in an has been added, it has to be mixed with a triethanolamine solution. This solution has
Erlenmeyer flask and titrated under strong agitation with 0.1 n KMnO solution. The to be slightly acidic so that the masking of iron by triethanolamine can be realized. If
titration is brought to an end when after the last addition of potassium necessary, some drops of hydrochloric or sulphuric acid can be used for adjustment.
permanganate, the solution still shows after one minute a light pink. The slight acidic solution is to be set ammoniacal with about 25 ml ammonia and
after the addition of Murexid, titrate with:
ml consumption 0.1 n KMnO4 x 1.1 = g Fe / l pickling solution ‘0.1 m Complexon-III-solution until the colour changes from brownish pink to deep
2+
violet.
Required reagents:
Reinhardt-Zimmermann-solution: ml consumption 0.1 m Complexon-III-solution x 1.1 = g NiSO 4 x 7H2O / I nickel

67 g MnSO4 x 4 H2O, 138 ml H3PO4 (density 1.70) and bath solution
130 ml H2SO4 (density 1.82) are to be filled up with 1000 ml distilled water. Required reagents:
0,1n potassium permanganate solution
Ammonium chloride: 54 g NH4Cl per Liter
Ammonia 25 %, p.a
Triethanolamine – solution: TriEthanol diluted in water in a proportion 1 : 1

Murexid: Murexid is mixed with NaCl in a proportion 1 : 200

0.1 m Complexon-III-solution:
Complexon-III-solution is the disodium salt of the ethylenediamine tetra acetic
acid (mol. weight 372.1) and is known under the trade name Titriplex (Merck)
®
®
and Idranal (Riedel de Haen).

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