pH Adjusters on a Filing: Citric Acid and Its Solution

Someone filing their first CNF asked me why their citric acid solution needed two lines on the ingredient list instead of one. It's a small detail, but it's the kind of thing that separates a filing that sails through from one that gets a clarifying question back.

The core confusion

Citric acid, INCI name Citric Acid, CAS number 77-92-9, is what most soap and skincare makers use as a pH adjuster, dropping the pH of a formula slightly to hit a target range for skin feel, preservative efficacy, or just to counter an alkaline ingredient elsewhere in the batch.

The catch is that very few makers are buying pure, dry citric acid powder and weighing out a precise fraction of a gram into a large batch. Most buy or make a citric acid solution, commonly a 50% solution in water, because it's easier to dose accurately in small amounts. That solution is not one substance, it's citric acid dissolved in water, and both of those need to be represented on your ingredient list.

What actually goes on the list

If your supplier's product is "50% Citric Acid Solution," you don't declare "Citric Acid Solution" as if it were a single INCI entry, because that's a trade description, not an INCI name. You declare:

• Citric Acid at its real concentration in your finished product
• Aqua (the INCI name for water) contributed by the solution, added to whatever other water is already in your formula

The math works the same way as any other supplier blend: multiply the concentration of citric acid within the solution by how much of that solution you added to the batch. If you added 1% of a 50% citric acid solution to your finished product, your actual citric acid concentration is 0.5%, not 1%, and the remaining 0.5% contributed by that addition is water, which gets folded into your total Aqua declaration alongside any water added separately.

A quick worked example

Ingredient added	Supplier concentration	Use level in formula	Real Citric Acid contribution	Real Aqua contribution
Citric Acid Solution (50%)	50% citric acid, 50% water	1% of finished product	0.5%	0.5%

If your formula also has, say, 70% water added directly as a base, your total Aqua declaration becomes 70.5%, not 70%, once you fold in the water that arrived via the citric acid solution. This matters for accuracy on the CNF even though water isn't a restricted ingredient, since the notification is meant to reflect your actual finished-product composition.

Why this matters beyond just being tidy

A few real reasons to get this right rather than shrugging it off as a rounding detail:

1. Concentration accuracy for anything else restricted in the same formula. If you're also tracking a preservative or another ingredient near a Hotlist limit, getting your percentages internally consistent across the whole formula matters, and sloppy handling of one ingredient's water content can throw off your total percentage accounting, which should sum sensibly across the whole product.
2. Consistency if you ever switch suppliers. A different supplier's citric acid solution might be 30% or 40% concentration instead of 50%. If you've been declaring "citric acid solution" as a single unexamined line item, switching suppliers without redoing the math means your filing no longer reflects what's actually in the bottle.
3. It's the same principle you'll hit constantly. Preservative blends, chelating agent solutions, most liquid surfactants, even some fragrance dilutions, all arrive from suppliers pre-diluted in water or another carrier. Citric acid is just the most common one people encounter first, so getting comfortable with the expand-and-multiply habit here sets you up for every other diluted ingredient in your formulary.

The practical habit to build

Before you declare any liquid ingredient on a filing, check the supplier's spec sheet or safety data sheet for its actual composition, not just its trade name. If it's sold as a percentage solution, that percentage is your multiplier, and the remainder is very often water that needs folding into your total Aqua figure.

This is exactly the kind of unglamorous but easy-to-get-wrong math that Cosmetic Comply handles automatically. Enter your citric acid solution at its use level and its labeled concentration, and it carries the real citric acid and water contributions through to the finished filing without you needing to do the arithmetic by hand for every diluted ingredient in the formula.