Which is more harmful to skin: soap or detergent?

[Docscientist]

Homework Statement

Amoung soap and detergent,which is more harmful to our skin?

Homework Equations

None

The Attempt at a Solution

Soap is what we use for bathing so if it is harmful we wouldn't have used it.The detergents are used for washing clothes more often.
So I think detergents are harmful.

 

[Drakkith]

Hi, Doc. Is this a homework question, or are you asking out of curiosity?

 

[Borek]

First of all - how do you define soap, how do you define detergent? Are the definitions exclusive, or overlapping?

 

[Docscientist]

Hi, Doc. Is this a homework question, or are you asking out of curiosity?

It's both,Mr Drakkith.
I have got my finals tomorrow.There was this one topic where I found something quite disturbing.It said "Soaps do cause irritation to skin while detergents do not."
But wasn't that supposed to be the other way round?

 

[Docscientist]

First of all - how do you define soap, how do you define detergent? Are the definitions exclusive, or overlapping?

Soaps are the calcium or potassium salts of higher carboxylic acids. Detergents are the ammonium or sulphonate salts of higher carboxylic acid.Soaps are made from vegetable oil or animal fats while detergents are made from hydrocarbons.

 

[Borek]

So sodium stearate is not a soap?

I was always under impression that detergent refers to the mode of action, and technically soaps are detergents.

Beware: seems like you are falling into a trap of "natural is safe, artificial is harmful". It doesn't work this way. Some things are safe, some are harmful, some are natural, some are artificial - these are completely unrelated classifications, and there is no correlation between them. Plenty of natural, dangerous things, plenty of artificial, perfectly safe ones. Each should be judged separately.

Solution of typical soaps - salts of higher carboxylic acids - are always basic (have high pH, because of hydrolysis). That never works well for the skin. Artificial detergents are not limited this way, solutions of some of the are neutral, or can work even when slightly acidic - and that's much better for the skin. It doesn't mean every artificial detergent is good, again - each should be judged separately.

 

[Docscientist]

So sodium stearate is not a soap?
I was always under impression that detergent refers to the mode of action, and technically soaps are detergents.

Sorry Mr Borek.Careless mistake.Soaps are sodium or potassium salts of higher carboxylic acid.Sodium stearate is a soap.
No Soaps are not detergents.Only one thing they have in common is that they are both good in cleansing action in soft water.

 

[Borek]

So lithium stearate is not a soap?

No Soaps are not detergents.Only one thing they have in common is that they are both good in cleansing action in soft water.

Do you understand that their mechanism of action is identical? How are you going to tell what is a detergent and what is not, if they work the same way?