How to prepare ammonium ferrous sulfate standard solution

How to prepare ferrous ammonium sulfate standard solution

Ammonium ferrous sulfate (chemical formula: Fe (NH₂) ₂ (SO₂) · 6H₂ O) is a commonly used chemical reagent, which is widely used in analytical chemistry, especially as a standard solution in titration experiments. How to prepare ammonium ferrous sulfate standard solution? This article will introduce the preparation of ammonium ferrous sulfate standard solution steps, precautions and its application.

1. Ammonium ferrous sulfate standard solution definition and use

Ammonium ferrous sulfate standard solution is mainly used in redox titration experiments in analytical chemistry, especially with oxidants such as potassium permanganate. It is a stable source of divalent iron and can provide accurate Fe²+ ion concentrations. Common application scenarios include water quality testing, iron content analysis, and medical research.

2. ferrous ammonium sulfate standard solution preparation steps

When preparing the standard solution of ammonium ferrous sulfate, it is necessary to follow certain steps to ensure the accurate concentration and stability of the solution. Here are the detailed steps:

1. Weigh ammonium ferrous sulfate According to the required concentration, accurately weigh the appropriate amount of ammonium ferrous sulfate solid. In general, the concentration of the standard solution is 0.1 mol/L, and the required mass of ammonium ferrous sulfate can be calculated by molar mass.

2. dissolved ammonium ferrous sulfate The weighed ammonium ferrous sulfate was dissolved in an appropriate amount of deionized water. To ensure complete dissolution, warm water can be used, with stirring to help dissolve.

3. Fixed volume to scale When the ferrous ammonium sulfate was completely dissolved, the solution was transferred to a volumetric flask and brought to the desired volume with deionized water. At this time, it is necessary to pay attention to the alignment of the surface of the solution with the scale line of the volumetric flask to ensure the accuracy of the solution volume.

4. Preservation solution The ferrous ammonium sulfate solution is easily oxidized, so it should be stored in a shading bottle after preparation, and try to avoid exposure to the air. An appropriate amount of sulfuric acid can be added to the solution to help reduce the possibility of oxidation.

3. How to ensure the ferrous ammonium sulfate standard solution accuracy?

In the preparation of ferrous ammonium sulfate standard solution, how to ensure the accuracy of the solution concentration is the key. The following points are crucial:

• Weighing Error Control When weighing ammonium ferrous sulfate, use a precision balance to ensure accurate weighing. Excessive errors may lead to deviations in solution concentration, which may affect subsequent experimental results.

• completely dissolved Ammonium ferrous sulfate may not be completely dissolved when dissolved, especially at low temperature. Therefore, complete dissolution should be ensured to avoid residual solids affecting the solution concentration.

• Accurate fixed volume When fixing the volume, make sure that the liquid level of the solution is exactly flush with the scale line of the volumetric flask. A little more or less solvent will affect the exact concentration of the solution.

• Avoid oxidation Ammonium ferrous sulfate solutions are easily oxidized to ferric ions Fe³ in the air, resulting in changes in solution concentration. Therefore, the preparation needs to be operated in a low oxygen environment and stored in a sealed, light-shielded container.

4. Ammonium Ferrous Sulfate Standard Solution Preservation and Stability

The stability of ferrous ammonium sulfate standard solution is poor, especially vulnerable to oxygen and light. In order to ensure the long-term stability of the solution, the following measures are necessary:

• sealed preservation The ferrous ammonium sulfate solution should be stored in a well-sealed bottle to prevent oxygen in the air from entering the solution and causing iron ions to oxidize.

• dark storage Light will also promote the oxidation of ammonium ferrous sulfate, so it is best to store the solution in a light-tight container or in a dark place.

• short-term use The storage time of ferrous ammonium sulfate standard solution is usually short, and it is generally recommended to use it within two to three weeks after preparation. If long-term storage is required, it may be considered to periodically check for changes in its concentration by titration.

5. How to verify the ferrous ammonium sulfate standard solution concentration?

After the preparation of ferrous ammonium sulfate standard solution, how to verify the accuracy of its concentration is an important step. A common validation method is titration with a known concentration of oxidant. By reacting with the standard solution, the actual concentration of ammonium ferrous sulfate in the solution is calculated to ensure that it meets expectations.

To sum up, the preparation of ferrous ammonium sulfate standard solution is not complicated, but requires precise operation and control. The correct preparation method, storage conditions and concentration verification method are the key to ensure the accuracy of the experimental results and the stability of the solution. It is hoped that through the introduction of this article, you can better grasp how to prepare ferrous ammonium sulfate standard solution.