I get that the vinegar is 4% -- no problem there -- but the OP also mentions sodium acetate, and I cannot figure out what's being added to the soap.
Is the OP adding sodium acetate in place of vinegar?
Or is the OP adding sodium acetate AND vinegar?
Or did the OP mentioning sodium acetate because that's what is created when vinegar reacts with sodium hydroxide, but is adding vinegar per the usual.
That's why I'm confused.
Anyways, here's a step-by-step method for using vinegar that is
4% acetic acid --
How much lye does vinegar neutralize?
About 1 fluid ounce (2 tablespoons, 1 ounce by weight, or 28 grams) of 4% commercial vinegar contains 1.2 g acetic acid.
1 oz by weight (28 g) of commercial 4% vinegar neutralizes about 0.8 g NaOH.
1 oz by weight (28 g) of commercial 4% vinegar neutralizes about 1.12 g KOH.
How to calculate the extra lye?
When using vinegar in your recipe, add the appropriate extra weight of lye needed to react with the acid. If you do not add any extra lye, the acid will increase the superfat in your soap.
Sodium hydroxide, NaOH
Decide how much vinegar to use. If you aren't sure, I suggest using commercial vinegar for half of the water in your recipe.
For example, if a recipe calls for a total of 200 grams of water, use 100 grams of vinegar and 100 grams of water.
NaOH for 4% vinegar, grams = Vinegar, grams X 1 / 28 X 0.8 = 0.0286 X Vinegar, grams
Total NaOH, grams = NaOH for vinegar, grams + NaOH for saponification, gram
As Earlene mentioned, vinegar sold in the US is typically 5% acetic acid. Here's my step-by-step for
5% vinegar --
Soapy Stuff: Acetic acid (Vinegar)