Determination of iron by titrimetric method

Determination of iron by titrimetric method

The essence of the method consists in the separation of iron compounds in the form of insoluble hydroxide, followed by the dissolution of the precipitate and the determination of iron by the titrimetric method in the presence of sulfosalicylic acid.

The sensitivity of the method - from 0.5 mg in the sample - from 5 mg / l.
The complete set is calculated on carrying out 50 definitions.
The set includes:
Reagents -
Trilon B, solution with a concentration of 0.01 mol / l.
Ammonia water - 1000 ml.
Ammonia water, 10% solution - 500 ml.
Hydrochloric acid, 5% solution prepared from standard fixanal - 1000 ml.
Sulfosalicylic acid, 10% solution.
Tableware
- Chemical glass V-1-250 THS
Flasks Kn-250 THS
The funnel is conical glass.
Measuring pipettes graduated to 1; 2; 5 ml
Additional instruments and materials for analysis:
Electric hob.
Distilled water (desalinated water).
Sample preparation for analysis.
A sample containing from 0.5 to 5 mg of iron is placed in a glass, if necessary, evaporated to a volume of 80-100 ml; add 20 ml of aqueous ammonia and boil until a flocculent precipitate is formed. After that, the precipitate is quantitatively transferred to the filter and washed several times with hot distilled water.
The precipitate on the filter is dissolved in 10 ml of 5% hydrochloric acid solution, washed quantitatively into a 250 ml conical flask. For complete transfer of iron, the filter is washed several times with water and the washings are collected in the same conical flask.
Проведение анализа.
1-2 ml of a 10% aqueous ammonia solution is added to the resulting solution (until a pH value of about 2 is reached), 1 ml of a sulfosalicylic acid solution is poured into the flask. The solution should acquire a rich wine-red color. Then the solution is heated to a temperature of 70-80°C and immediately, without allowing it to cool, is titrated with a solution of Trilon B with a concentration of 0.01 mol/l until the wine-red color changes to straw-yellow.
The iron content in the sample (mg) is calculated by the formula:
XFe (mg) = 56 x V x 0.01, where
56 - molecular weight of iron, mg/mmol;
V is the volume of Trilon B with a concentration of exactly 0.01 mol/l, used for sample titration, ml;
0.01 - molar concentration of trilon B, mol/l.
The concentration of iron in the sample (mg/l) is calculated by the formula:
CFe (mg/l) = XFe /V samples, where
XFe - iron content in the sample (mg);
V - sample volume, l.