What is the Difference between Soap and Detergent?

Castellet-Soap Is there a difference between soap and detergent? Both clean what they are made to clean. But, yes, there are  differences. They come from different sources. They are different chemically. And they are put to different uses. An example of each is provided, below.

Soap

There are a variety of soaps. A soap is the metal salt of a fatty acid.

A fatty acid is an organic compound most often of animal or plant origin. A fatty acid contains a long-chain aliphatic carbon skeleton (with or without branches) plus a carboxylic acid group (-COOH) at its end.

The metal may be an alkali metal such sodium (Na) or potassium (K). These metals are found in the first column of the periodic table of the elements. Or, the metal can be an alkaline earth metal, such as calcium (Ca) or magnesium (Mg). These metals are found in the second column of the periodic table of the elements.

Detergent

Detergents have some similarities. But are often of synthetic origin. They are not made insoluble by hard (mineralized) water. Instead of a carboxylic acid group, detergents contains a more intensely ionic group. It may be a sulfate or a sulfonate group (-OS(O)₂-OH).

difference between soap and detergent

In addition, detergents can include aromatic rings. Detergents can also be used as surfactants and foaming agents.

There are even detergents that dissolve in solvents other than water, such as gasoline. These often include nitrogen in their formulation. The nitrogen compound frequently includes a ring as part of its structure. Such compounds are not only detergents, but dispersants.

Example Difference Between Soap and Detergent

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:difference between soap and detergent

CH₃(CH₂)₁₂-OS(O)₂-O⁻ Na⁺

Note: You might also enjoy Ammonia and Bleach – Why a Bad Choice?

References: ← Back to Food-Health
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14 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. 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

    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.

    • G Namchuk Reply

      I would also like to know the difference in the mechanisms of the two different types of molecules (soap vs detergent), so am asking one of you/someone to reply to that question. I just finished reading an article about garlic used as an insect repellant which specified using a soap rather than a detergent (for dogs), which is why I was looking for the difference between the two. So, while I liked the article, I don’t really have an answer to my original query about why a soap may be preferable to use in certain applications over a detergent. Also, – separate topic – What is the purpose of the italicizations in your article? The italicized words in your article seem to need definitions, but on my iPad there are no hyperlinks.

      • Vincent Summers Reply

        Many of the italicized words in the article are defined within the article. Those that are not can be understood by searching the word online. For instance, enter: Define: dispersant.

  • Tim Knight Reply

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

  • ALLWIN AROCKIARAJ.M Reply

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

  • Neba Kalvin Reply

    Is it advisable to use a detergent just after production?

    • Vincent Summers Reply

      Please elucidate (explain further). Just after what is produced?

  • Patti Crossley Reply

    Molecularly, how do they differ in the cleaning process? My Dad once told me that one of them wraps the dirt (I think that was the soap) and lifts it up, and the other dissolves the dirt — which is which, and is this accurate in any way?
    Thank you very much.
    Patti

    • Vincent Summers Reply

      Soap ionizes in water. The fatty portion of soap attaches to the dirt. Micelles form around the dirt, enabling it to be all washed away. Detergents are stronger, synthetic chemicals that act primarily as surfactants. They loosen the dirt from the dirty object.

  • Amy Reply

    Is it advisable to use soap to wash laundry in a washing machine then?

    • Vincent Summers Reply

      It’s up to you, as long as you are careful to limit quantities so sudsing isn’t excessive. Personally, I’ll stick to detergent.

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