5 How to prepare the chromogenic solution of ammonium ferrous sulfate

Experimental instruments: graduated cylinders, beakers.

1000ml volumetric flask.

Glass rods, balances, balance paper, rubber tip droppers, medicine spoons.

Drug: Ferrous sulfate.

powder (or ferrous sulfate crystals), distilled water.

Experimental procedure: Weighing: Weigh 50 grams of ferrous sulfate with a balance (balance paper should be lined on both sides of the balance).

Dissolve: Put the weighed ferrous sulfate into a beaker and dissolve it with an appropriate amount (20 30 ml) of distilled water.

Rewarming: Allow the solution to cool and move into a volumetric flask. (Pipetting if you do not wait for the solution to cool will result in the desired concentration of the solution.)

on the small side). Pipetting: Due to the thin neck of the volumetric flask, in order to avoid the liquid from spilling outside, drain with a glass rod, the glass rod can not be close to the mouth of the volumetric flask, and the bottom of the rod should be leaning against the scale line of the wall of the volumetric flask (if the bottom of the glass rod is on the scale line, the concentration of the prepared solution will be low).

Washing: Wash the inner wall of the beaker 2 3 times with a small amount of distilled water, **, and transfer the washing solution all to the volumetric flask.

Volumetric setting. Add distilled water to the volumetric flask, and when the liquid level is 1 2cm below the volume bottleneck scale line, use a rubber head dropper to add distilled water dropwise until the liquid level is tangent to the scale mark.

Shake well, close the cork and turn it upside down repeatedly, shake well, if the liquid level drops, do not add water to determine the volume (if you add water again, the concentration of the prepared solution will be low).

Since the volumetric flask cannot hold the solution for a long time, the prepared solution is transferred to the reagent bottle and labeled.

This results in a 5% ferrous sulfate solution.

<> ferrous sulfate ionized after dissolving in water has strong reducing property and can also undergo hydrolysis reaction to a large extent. The configuration of ferrous sulfate solution can not directly add ferrous sulfate solid to water to dissolve, the correct preparation method is:

1. Add ferrous sulfate solids to dilute sulfuric acid to prevent hydrolysis to form ferrous hydroxide;

2. After dissolving, add a small amount of reduced iron powder to prevent ferrous ions from being oxidized by dissolved oxygen.

Preparation method: weigh ammonium ferrous sulfate and dissolve it in an appropriate amount of water, add 100ml of sulfuric acid solution, dilute it to 1L with water, and store the solution in a brown bottle.

Calibration method: Absorb the potassium dichromate standard solution into a 500ml Erlenmeyer flask, dilute it to about 110ml with water, slowly add 30ml of concentrated sulfuric acid, and mix well. After cooling, add 3 drops of ferrous sulfate indicator solution (approximately, titrate with ammonium ferrous sulfate solution, the color of the solution changes from yellow to blue-green and finally to reddish-brown is the end point.

Ammonium ferrous sulfate is blue-green.

Molecular Formula: CH3SSH3 CAS No. 624-92-0, Properties: Light yellow transparent liquid. Insoluble in water, can be combined with ethanol.

Acetic acid miscibility. There is a foul smell. Relative density d(204). Boiling point. Melting point -85. Refractive index.

ND(20), use: used as catalyst, passivator and pesticide intermediate, toxicity: mice die after inhaling 25 mg L for 25 min.

Ferrous sulphate ammonium in the hole.

It is a kind of chemical raw material that is important for banquets, and it is very widely used. It can be used as a water purification agent; In the inorganic chemical industry, it is used as a raw material for the preparation of other iron compounds, such as iron oxide.

It is pigments, magnetic materials, yellow blood salts and other iron salts.

It also has many direct applications, such as being used as a mordant in the printing and dyeing industry, tanning in the tanning industry, and as a preservative in the wood industry.

It is used in medicine for iron deficiency anemia.

It is used in agriculture for iron-deficient soils, as a feed additive in animal husbandry, etc., and can also be used with tannic acid.

Gallic acid and other mixtures are combined with blue-black ink.

The above content reference: Encyclopedia - ammonium ferrous sulfate.

Potassium dichromate method:

cod(o2,mg/l)=[v0-v1)*c*8g/mol*1000]/v

C--The concentration of ammonium ferrous sulfate standard solution, mol LV0 - the volume of ferrous sulfate as a closed ammonium standard solution when titrating blank, ML1 - the volume of ammonium ferrous sulfate standard lead-containing quasi-solution when titrating water samples, MLV - the volume of pure old fission of water samples, ml

8g mol - oxygen (1 2o) molar mass.