Detergent in our daily use

I think everyone tried before stained your lovely shirt with coffee and whatever that make your shirt dirty. And after you soak in the water with detergent, the stubborn stains and dirt disappear. Do you know what are they in your detergent to help you wash away the grease, oil and dirt? And how the detergent and soap wash way the grease?

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Detergent

Detergent is a salt that formed from neutralization between alkyl hydrogen sulphate and an alkali. The most effective detergent is Sodium Lauryl Sulphate, C₁₂H₂₅NaO₄S.

First process involve the production of lauryl hydrogen sulphate,

lauryl alcohol, CH₃(CH₂)₉CH₂OH + sulphuric acid, H₂SO₄→ lauryl hydrogen sulphate, CH₃(CH₂)₉CH₂OSO₃H + H₂O

Second process involve the neutralisation of lauryl hydrogen sulphate,

lauryl hydrogen sulphate, CH₃(CH₂)₉CH₂OSO₃H + sodium hydroxide, NaOH → sodium lauryl sulphate, CH₃(CH₂)₉CH₂OSO₃Na + H₂O

The chemistry structure in the above is sodium lauryl sulphate, the circle part is polar end which is negatively charged and it is hydrophilic which attract water. The tail part is non-polar end and has no charge. It is hydrophobic which repel water. The pictures below show how the detergent remove the grease on the shirt.

First, the hydrophobic tail of the anion part dissolves in the grease which is shown as brown colour, the hydrophilic part dissolves in the water.

After that, the grease started to loosen and lift off from the surface of the shirt . Therefore, rubbing and scrubbing help to faster the loosen of the grease from the surface of the shirt.

The grease is surrounded by the anion part and the grease is total lifted off from the surface of the shirt and suspended in water.

Besides that, there are many substances added into the detergent. For example, surfactant, biological enzymes, water softener and optical brightener.

Surfactant is added to keep oil and water from forming into layers. Surfactant have a hydrophilic side and hydrophobic side. The hydrophobic side stick to the oil or grease and hydrophilic side stick to the water. Surfactant also lower the surface tension of the water to allow detergent to wet surface and penetrate into, under, and around the grease.

Biological enzymes are the enzymes that digest protein, fats and carbohydrate on the shirt so it make the stain on your shirt disappear. For example, amylase digest starch stain, lipases digest oil stain and protease digest protein stain.

Optical brightener are used to enhance the appearance of the colour of shirt. Optical brighteners absorb ultraviolet radiation and re-emit the blue light and reduce the yellow colour of the shirt and make it become whiter. For example, fluorescent. Fluorescent contain phosphor which is the substance that emits visible light in response to some sort of radiation. A phosphor converts the energy in the UV radiation from a black light into visible light.

Water softener is used to reduce the calcium ions and magnesium ions in the hard water and make reduce the formed of the scum. Water softener based on the ion exchange principle which the calcium ions and magnesium ions are exchanged for sodium or potassium ions to make the water softer and give it a smoother feeling. Examples of the water softening are potassium chloride and sodium chloride.

How tha scum is formed on the shirt?

Scum normally is formed by using soap because soap contains salt such as Sodium stearate and Sodium palmitate , when calcium ions and magnesium ions in hard water mix with it, a insoluble salt is form which is Calcium stearate / Calcium palmitate.

Ca2+ (aq) + 2C₁₇H₃₅COO-(aq) ----> 2C₁₇H₃₅COOCa(s)

Of course, different detergent companies have their own "formula" in making their detergents. The chemicals that i introduce in the above are only some common and important ingredients in detergent.

Hope you enjoy the details of the detergent.