What is the Difference between Soap and Detergent?

There is a difference between soap and detergent.
Castellet Soap

Is there a difference between soap and detergent? Both clean what they are supposed to clean. The two have a different chemistry and functionality.

Soap

A soap is the metal salt of a fatty acid. The metal may be an alkali metal such sodium (Na) or potassium (K). It can also be an alkaline earth metal, such as calcium (Ca) or magnesium (Mg). A fatty acid is an organic compound most often of animal or plant origin. A fatty acid contains an aliphatic carbon skeleton (a chain with or without branches) and a carboxylic acid group (COOH) at its end.

Detergent

Detergents bear some similarity, but are often of synthetic origin. They are not usually made insoluble by mineralized or so-called hard water. Instead of a carboxylic acid group, the detergent contains a more highly ionic group, such as a sulfate or sulfonate group (OS(O)₂-OH).

In addition, detergents may contain one or more aromatic ring. Detergents possess added properties. They may be employed as surfactants and foaming agents.

Example Difference Between Soap and Detergent

An example of a soap is potassium palmitate: CH₃(CH₂)₁₄-COO⁻ K⁺

An example of a detergent is sodium lauryl sulfate: CH₃(CH₂)₁₂-OS(O)₂-O⁻ Na⁺

References:

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6 Comments

  • Barbara Reply

    I did not know these facts. Quite fascinating.

  • MegL Reply

    In the UK, most shampoos and shower gels are detergents, as is what we term “washing up liquid”, which I think Americans call “dish soap”. Mt granddaughters love bubble bath (detergent) but it is so hard to get the bubbles to drain after the bath but I have found that washing your hands with a piece of soap in the detergent water helps get rid of the bubbles. They seem to work against each other!

  • Styra Avins Reply

    I wish there were more information here. In my experience, detergent is much better at dissolving fats, without leaving any residue. If you wash your hair with soap, you will find it very difficult to rinse thoroughly. If you have been in poison ivy and need to wash the irritant oil off your skin, detergent is far more effective than even soap made with lye. (East coast of the USA, I have years of experience on this point!). On the other hand, soap is much nicer! I use brown soap for wiping my kitchen sink and surfaces. But my question is still, in what way does detergent work differently from soap? What is the mechanism of the soap molecule vs. the detergent molecule?
    Thank you.

  • Tim Knight Reply

    I don’t care for detergent but this article gave the right information on what the difference between the two are.

  • ALLWIN AROCKIARAJ.M Reply

    It was really helpful to know what is the difference between soap & detergent in a simple way.

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