How to test the iron content of water 10

Leave the water for a long enough time to turn the iron into Fe3+, and then drop it into KSCN to try, if it can appear red, it means that the iron content is very high.

There are many methods for the determination of ferric oxide content, such as potassium dichromate titration, potassium permanganate titration, EDTA complexation titration, ultraviolet-visible spectrophotometry (sulfosalicylic acid or phenopyroline spectrophotometry), atomic absorption spectrophotometry, etc.

Potassium dichromate volume method.

The sample is decomposed by acid or alkali melt decomposition, the test solution is reduced to Fe2+ ions with stannous chloride, and the excess stannous chloride is oxidized with mercuric chloride, and in the presence of sulfuric acid and phosphoric acid mixed acid, sodium diphenylamine sulfonate is used as an indicator, and the potassium dichromate standard solution is titrated to purple. The reaction equation is.

Modern rock and mineral analysis experiment tutorial.

This method is suitable for the determination of total iron content of samples with a total iron content greater than 5%.

The SNCL2-HGCL2-K2Cr2O7 method was used to measure iron, and the method was mature and accurate. However, due to the use of HGCL2, the harmful element HG is introduced into the environment, causing environmental pollution, which is the biggest disadvantage of this method for iron measurement.

Potassium permanganate titration.

The principle of potassium permanganate titration is basically the same as that of potassium dichromate titration. In the pretreatment, stannous chloride was used to reduce iron to Fe2+ ions, and the titrant was acidic potassium permanganate solution. In the acidic solution, potassium permanganate reacts with ferrous ions, permanganate ions are reduced, iron ions are oxidized, and a slightly excess of potassium permanganate at the end point makes the solution appear reddish.

The reaction equation is.

Modern rock and mineral analysis experiment tutorial.

EDTA complexation titration.

Based on the fact that Fe3+ can form a stable complex with EDTA in acidic solution, in the acidic solution of pH=, with sulfosalicylic acid (SS) as the indicator, at 60 70, FE3+ in the solution was directly titrated with EDTA, and the end point changed from purple-red to bright yellow. The reaction is as follows:

fe3++h2y2-=fey-+2h+

fe3++ssal2-=fe(ssal)+

fe(ssal)++h2y2-=fey-+ssal2-+2h+

The direct determination of iron using SS as an indicator and EDTA is a simple method that makes it easy to observe color. However, the biggest disadvantage is that the ** rate does not meet the requirements, generally 99%, and the error caused by the silicate sample with low iron content is not large.

However, for samples with high iron content, such as iron ore, large errors can occur. To improve accuracy, xylenol orange can be used as an indicator and back-titrated with a bismuth salt standard solution.

UV-Vis spectrophotometry.

When the iron content is low, it can be determined by photometric colorimetry. Sulfosalicylic acid photometry is suitable for the determination of total iron, and phenopyroline spectrophotometry is suitable for the determination of total iron.

The determination of trace iron in water is as follows:

1.Determination of the wavelength of liquid start.

The chromogenic solution is prepared in six 25 ml volumetric flasks with serial number 1 6.

, use a pipette to accurately add the UGML-1 iron standard solution00ml, and then add 10% hydroxylamine hydrochloride respectively.

Solution 1 ml. After shaking well, it was placed for 2min, and then 1moll-1naac solution and o-diazaphenanthrene were added.

1ml of solution, after each reagent is added, shake well (do not cap) the solution in the volumetric flask, add another reagent, and finally dilute it with water to the scale, cover and shake well.

The absorption curve is measured in a spectrophotometer.

, the absorbance of the 4-iron standard solution was measured at 10 nm intervals between 450-550 nm using a 1 EM absorption cell and a reagent blank solution (1) without iron as a reference.

a (Accurate reading to +.)

The absorption curve was plotted with the wavelength as the abscissa and the absorbance as the ordinate rise, so as to select the maximum absorption wavelength amax for the determination of iron. [Note] After each wavelength change, calibrate the instrument and adjust the absorbance value of the instrument with the reference solution.

2.Drawing of standard curves.

Using the reagent blank solution as a reference, the absorbance of each chromogenic standard solution of No. 2 6 was determined at the selected wavelength with a 1 cm absorption cell. On the coordinate paper, the concentration of iron is used as the abscissa and the corresponding absorbance is the ordinate, and the standard curve is drawn.

3.Determination of iron solution in the sample.

Aspirate the unknown solution, and measure its absorbance under the same conditions and steps as the standard curve above. According to the absorbance ax of the unknown solution, the amount of iron corresponding to the unknown solution is found on the standard curve, and then the amount of trace iron in the sample is calculated, which is expressed as how many grams of iron per liter of unknown solution (GL-1).

(1) The principle of ferrizine colorimetric method: serum iron and ferritin are combined into a complex, and the iron is dissociated from the complex in an acidic medium, and then reduced to divalent iron by the reducing agent, and a purple-red compound is formed with ferrizine, and there is an absorption peak at the wavelength of 562nm, and the serum iron content can be obtained by comparing with the standard solution of the same treatment.

(2) Duplex pyridine colorimetric method: under acidic conditions, iron is freed from the protein-bound state. Hydroxylamine hydrochloride was used as a reducing agent to reduce the trivalent iron in the serum to ferric iron, which reacted with the double pyridine chromogenic agent to form a red chelate, which was colorimetric and quantified at 520 nm.

This method is simple and rapid, but the sensitivity is poor, and there are many interference factors, especially iron pollution. Hemolysis can also affect the results.

(3) Phenolizine colorimetric method: trichloroacetic acid-hydrochloric acid mixture releases the iron in the serum from ferritin and enables the protein precipitation to be collected and sorted out. The released ferric can be reduced to ferric iron by thioglycolic acid, which is combined with phelozine to form a purplish-red compound with an absorption peak of 562 nm.

Methods for the determination of iron content in water:

The amount of iron in water is often expressed in terms of total iron (mg l). Potassium thiocyanate colorimetric method can be used for determination.

Fe3++3SCN-=Fe(SCN)3 (red).

1.Determination method of iron content in water: Experimental principle The total amount of iron (mg l) is often used to express the iron content in water.

Potassium thiocyanate colorimetric method can be used for determination. Fe3++3SCN-=Fe(SCN)3 (red) Experimental operation 1 Prepare relevant reagents (1) Prepare ammonium iron sulfate standard solution Weigh G analyze pure NH4Fe(SO4)2·12H2O dissolved in 50 ml of distilled water in an Erlenmeyer flask, add 20 ml of concentrated sulfuric acid of 98, shake and mix well, heat, add mol L of KMNO4 solution drop by drop after a while, and fully shake and mix each drop until the solution is reddish. Inject the solution into a volumetric flask of l 000 ml and dilute to l 000 ml with distilled water.

This solution contains mg ml of iron. (2) Prepare potassium thiocyanate solution Weigh 50 g of pure potassium thiocyanate crystals, dissolve them in 50 ml of distilled water, filter them and set aside. (3) Prepare nitric acid solution Take 191 ml of chemically pure nitric acid with a density of g cm3 and slowly add it to 200 ml of distilled water, stir while adding, and then dilute to 500 ml with a volumetric flask.

2 Preparation of standard colorimetric solution Take six 50 ml colorimetric tubes of the same specification, add ml, ml, ml, ml, ml ammonium iron sulfate standard solution respectively, dilute to 40 ml with distilled water, then add 5 ml nitric acid solution and 1 drop of 2 mol l kmno4 solution, dilute to 50 ml, and finally add l ml potassium thiocyanate solution to mix well, and put it on the colorimetric rack for colorimetry. 3 Determine the total iron content of the water sample Take 40 ml of water sample and put it in a clean Erlenmeyer flask, add 5 ml of nitric acid solution and heat and boil for several minutes. After cooling, it was poured into a colorimetric tube of the same specification as that used for the standard colorimetric solution, diluted to 50 ml with distilled water, and finally 1 ml of potassium thiocyanate solution was added, mixed well, and compared with the colorimetric tube listed above.

The "equivalent ammonium iron sulfate standard" refers to the volume of the ammonium iron sulfate standard used in the preparation of the standard colorimetric solution.