# Sodium PCA 50% question

Member
So if my formula calls for 2.5% sodium pca and the one I bought from lotion crafter is sodium pca 50% do I need to add more sodium pca and less water?

• Member
Gotta be careful with wording because of the misunderstandings that can come with it. You don’t add more sodium PCA, you will still add 2.5% of your total weight of actual sodium PCA.

Here’s a good read on calculating dilutions: http://dilutions.quansysbio.com/dilutions-explanations-and-examples/

For most basic formulas you’re concerned with C1V1 = C2V2

However, for cosmetic formulations we do everything by weight (not by volume) so you just need to replace V (volume) with W (weight).
• Member
You want to end up with 2.5 % sodium PCA but it comes as a solution with 50% pca.  So if you added  2.5% of your material, you would really only have 2.5*.5 = 1.25% sodium pca

Following letsalcidos system you would set it up like this:
(x) what % of your lotioncrafter material to put in multiplied by
(0.5) 50% concentration of your lotioncrafter material)
=
(2.5%) how much pca you want to end up with  multiplied by
(1) 100% 'pure' sodium pca concentration

x*0.5 = 2.5 *1

solve for x

• Member
Ok, I think I understand you guys. I also just plugged it into an already set up calculator. And basically it said use double since it's only at 50% solution so I use 5g instead of 2.5 g (my total was a 100g formula). My question I guess then does the water portion % of my formula change since 50% of the solution is water of the sodium pca solution? Thank you!

• Member, Pharmacist
Sure, subtract 2.5 g from your water phase and that keeps everything at the amounts it should be.
• Member
Thank you!