How to apply ferrous sulfate heptahydrate and its properties

How to apply ferrous Sulfate heptahydrate is a question that arises frequently on tests. The answer is not all that complex. The two major substances in ferrous sulfate heptahydrate are, of course, iron and sulfate. The "hydrate" means that it is has water molecules bound to the molecule. The heptahydrate indicates that there are seven water molecules bound to the iron. The "hepta" means 7, and "hydrate" means H₂O (water).

It has been used commercially to prevent corrosion in iron pipes and to make a green dye for wool yarn when mixed with copper sulfate and potassium chloride. The anhydrous salt has also been used as a control substance in some drug prescription tests. Anhydrous ferrous sulfate can be prepared by dissolving iron in sulfuric acid until the solution is clear, and then evaporating the liquid to leave a white powder. If no precipitate forms, then enough acid has been added. This is how to apply ferrous sulfate heptahydrate.

Physical properties of ferrous sulfate heptahydrate

1. Melting point: ( -1.6 ¡ ) 30-32 ℃

The melting point of this compound is -1.6  ¡, which is lower than the melting point of heptahydrated iron(II) carbonate . The reason for this difference is that ferrous sulfate heptahydrate has more empirical formula FeSO₄·7H₂O due to its higher oxygen content, so there is excess water in FeSO₄·7H₂O compared with Fe(CO₃)₂(OH). Fe(CO₃)₂(OH) is only 56.7% water.

2. Density of solution: (1.0 M), 0.98 g/cm³

This means that the density of ferrous sulfate heptahydrate solution is 1.0 M. For example, if you dissolve 0.5 g of a substance in a certain volume of water at room temperature, then the density will be 1.0 g / cm³, which is equivalent to the density of pure water.

3. Melting point (1.0 M) , 21 ℃

The melting point (1.0 M) means that the substance exists in its solid state as long as it is at or below its melting point at room temperature (1 ℃). If the melting point is higher than that, then it exists as a liquid at room temperature. For example, if you put the material in water at room temperature, it will turn into a liquid.

4. Specific gravity of solution (1.0 M): 0.98 g/cm³;

Specific gravity of the solution refers to the density of heptahydrated iron(II) salt solutions, which is comparable to that of a saturated non-heated or unstirred solution . If the specific gravity is less than 1 g / cm³, then you can use 1:1 dilution to test for saturation with sodium chloride, using 2 solutions - one containing sodium chloride and one without it. If the specific gravity is larger than 1, then add a small amount of distilled water and stir to dissolve the salt.

5. Solutions in boiling water, from volatile substances (water-soluble salts): 7H₂O = 56%

This is a type of compound that consists only of anion and cation (+ OH^-). Here we are talking about ferrous sulfate heptahydrate FeSO₄·7H₂O, which has a formula weight of 179.13 g/mol and an H (aq) solubility at 25 ℃: 56%. This means that you need 56 grams of water to dissolve 1 g of ferrous sulfate heptahydrate.

6. Ground state densities (1.0 M)

The ground state density refers to the density of a substance as it exists as a solid, liquid or gas at standard temperature and pressure. The density of ferrous sulfate heptahydrate is 397 g / cm³, which is larger than the saturation density of sodium chloride, since it is an ionic compound with large negative and positive ions. So, you need only small amounts of water to dissolve it in water.

Uses of ferrous sulfate heptahydrate

1. As a green dye, used in the production of wool yarn

Ferrous sulfate heptahydrate is mostly used as a green dye for wool yarn. There are two types of dyes based on this compound; one is a mixture of ferrous sulfate heptahydrate with potassium chloride and a small amount of copper sulfate, and the other is ferrous sulfate heptahydrate solution with copper sulfate. If you mix the two solutions together, then you will obtain the best results. In addition to providing color to the product, these dyes have antimicrobial effects.

2. As a corrosion inhibitor in iron pipes

In some cases, ferrous sulfate heptahydrate has been successfully used as a corrosion inhibitor in iron pipes. It is important to dissolve the compound in sulfuric acid and then evaporate the solution until no more particles appear. If you add sulfuric acid too slowly, then you will see precipitation of a solid precipitate.

3. Control substance for some drug prescription tests

In virology, ferrous sulfate heptahydrate has been used as a control substance for some drug prescription tests that require an oxidizer (such as drugs with antiseptic effects). Ferrous sulfate heptahydrate easily absorbs oxygen from the air and becomes oxidized to ferric ion, which is biologically inactive because of the presence of a positive charge. If ferrous sulfate heptahydrate is used for drug prescription tests, then a small amount of it will be added to each test tube as control substance.

In conclusions, how to apply ferrous sulfate heptahydrate is very important. After mixing the compounds together, you need to stir and dissolve the mixture in water. If you add too much water, then it will cause precipitation and you will see particles or crystals in the solution. If you evaporate it too quickly, then the sodium will be contained in the liquid and not precipitate (it is called flat-layered precipitation).