Why is citric acid in shampoo and conditioner?

A. citric acid isn't used because of the smell. Fragrances are added for that purpose. It has a two-fold reason for addition. Shampoos usually are at pH 5.5 because at slightly acidic pH the scales on a hair follicle lay flat making the hair feel smooth and look shiny. citric acid is used to adjust the pH down to 5.5 (ish). It is a fairly weak acid which makes the adjustment easier. it also has a small amount of preservative action. citric acid as opposed to any other acid will prevent bacterial growth. (I used to work in the lab for a cosmetics company)

"I used to work in the lab for a cosmetics company"

It shows, Ciaron. Thanks for the great answer!

!! Hey thanks for the great answer! It really helped me on my science fair project!

A. The full definition of pH is: "the negative antilog^log of the hydronium ion concentration", but I don't know if that wording is beyond your grade level, Pat. The easy way to look at it is that a pH of 0 is as acidic as you can get, a pH of 14 is as alkaline as you get, and a pH of 7 is neutral.

Depending on what grade you're in, you may or may not have been taught logarithmic scales. In a logarithmic scale you "count the zeroes". So your pH of 5.5 is slightly acidic, but it's less acidic than a pH of 5.0. And in turn, a pH of 5.0 is only one-tenth as acidic as a pH of 4.0, only one-hundredth as acidic as 3.0, only a thousandth as acidic as 2.0, etc. Good luck!

July 18, 2012

Thanks T.J.

You're right that pH is the negative log, not the negative antilog; thanks for correcting a silly mind-slip.

Kids from 3rd grade come to this site, and so do post-docs who are way beyond my level; but we often don't know who's who, and there are a hundred readers for every poster anyway. So starting with "depending on your grade level" seemed a good way to avoid patronizing people. On the other hand your use of "beyond your grade level" was deliberately insulting. You certainly realize that a P.E. knows what logarithms are, so ask yourself why you would publicly post that?

For 23 years now we've worked hard to make this site "... a place of camaraderie ... offering a friendly, welcoming atmosphere ...striving to live aloha". So I'd appreciate if you saved ALL CAP, multiple exclamation point, snide comments for your Youtube and Facebook postings. Pat and I aren't the only ones in this conversation who still have something to learn.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Ciaron Murphy already answered this question on this page, Christopher. If it wasn't clear enough, please rephrase your question in terms of the answer that he already gave, so that you can feel comfortable that you used this site to learn, not to ask someone to post an answer to cut & paste for your homework ? Thanks!

A. Hi, Sarah. Half of that answer is on this page already. Please try your best to phrase your question in terms of what has already been said so that we can keep moving forward. Thank you.

Regards,

A. Hi, Trina.. Citric-based means based on citric acid , which is an acid in citrus fruits. But chemical formulations are complex. You should probably ask the manufacturer for the MSDS for this product (material safety data sheet) and pass that on to your customer. Good luck.

Regards,