Chemical Properties of Hydrogen Sulphide

Chemical Properties of Hydrogen Sulphide

H2S (hydrogen sulphide) is a colourless gas that smells like rotten eggs. Because of its density, it is heavier than hydrogen. Humans and animals alike are poisoned by hydrogen sulphide. Just a modest percentage in the air induces headaches and nausea, but the worst thing is that if you breathe it for long enough, you may lose your ability to smell it.

If you’ve been poisoned by hydrogen sulphide, though, there’s a simple antidote: smell a handkerchief steeped in acetic acid with a bit of lime chloride rolled in it.

At a temperature of 350°C, sulphur reacts with hydrogen to produce hydrogen sulphide:

H₂ + S → H₂S↑

As the degrees of oxidation of the elements alter, this is an oxidation-reduction reaction. Before taking a look at the chemical properties of hydrogen sulphide, let’s discuss the uses of hydrogen sulphide!

Hy­dro­gen sulphide in na­ture and prac­ti­cal ap­pli­ca­tion:

Volcanic gases, natural gas, and gases found in oil fields all lead to the production of hydrogen sulphide. It is abundant in natural mineral waters; for example, in the Black Sea, it can be found at depths of up to 150 metres.

Here is a list of the uses of hydrogen sulphide:

• treatment with hydrogen sulphide baths and mineral waters in medicine;

• obtaining sulphur, sulphuric acid, and sulphides in the industry;

• in analytical chemistry – for the precipitation of sulphides of heavy metals that are normally insoluble;

Properties of hydrogen sulphide

Now let’s take a look at the chemical properties of hydrogen sulphide:

Sulphur ox­ide and water vapour form during the combustion of hydrogen sulphide:

2H₂S + 3О₂ → 2Н₂О + 2SO₂

H2S has a bluish flame, and if you hold an upturned beaker over it, trans­parent drops of condensing water from the water vapour will form.

If the temperature is reduced slightly, however, this reaction takes place in a slightly different way, a yellow coat of free sulphur appears on the cooled beaker’s walls:

2H₂S + О₂ → 2Н₂О + 2S

This reaction is the basis of the industrial method of obtaining sulphur. An explosion occurs when a prepared gaseous mixture of hydrogen sulphide and oxygen is heated. It is also possible to obtain free sulphur by reacting hydrogen sulphide and sulphur oxide:

2H₂S + SО₂ → 2Н₂О + 3S

Three volumes of hydrogen sulphide can dissolve in one volume of water, forming weak and unstable hydro sulphuric acid (H2S). Hydrogen sulphide water is another name for this acid. As you can see, hydrogen sulphide gas and hydro sulphuric acid have the same formula.

When you mix a lead salt solution with hydro sulphuric acid, you get a black sediment of lead sulphide:

H₂S + Pb(NO₃)₂ → PbS + 2H­NO₃

This is the qualitative hydrogen sulphide detection reaction. It demonstrates hydro sulphuric acid’s ability to enter into an exchange reaction with salt solutions. As a result, any soluble lead salt can be used as a hydrogen sulphide reagent. Other metal sulphides have distinct colours, such as zinc sulphide (ZnS), cadmium sulphide (CdS), copper sulphide (CuS), and antimony sulphide (Sb₂S₃).

 Hydrogen sulphide is an unstable gas that, when heated, breaks down almost completely into hydrogen and free sulphur:

H₂S → Н₂ + S

The hydrogen sulphide interacts intensely with aqueous hydrogen solutions:

H₂S + 4Cl₂ + 4H₂O→ H₂­SO₄ + 8HCl

Health effects

The physiological effects of hydrogen sulphide inhalation are proportional to the amount of gas inhaled. Even in low quantities, hydrogen sulphide has safety hazards because it is both an irritant and an asphyxiant. Hydrogen sulphide irritates the eyes, nose, and throat at low doses. Children and people with weakened lungs are particularly vulnerable to these side effects.

In some quantities, hydrogen sulphide can knock you out in a matter of breaths or kill you almost instantly. Hydrogen sulphide can kill you in an hour at concentrations as low as 500-700 ppm, and it can do so in seconds at concentrations as low as 1000-2000 parts per million. Headaches, memory loss and cardiovascular issues are some of the side effects of exposure. When exposed to hydrogen sulphide regularly, it can cause eye inflammation, irritability, insomnia and weight loss.

Conclusion

The large range of targets engaged resulted in the diverse effects generated by H₂S. Despite the efforts, the mechanisms of action that should shed light on the pharmacological effects remain unknown. Nonetheless, medicinal chemists have made several attempts to exploit this molecule’s multifarious profile, and multiple chemical properties of hydrogen sulphide containing an H₂S-releasing moiety have been determined.