Hydrotrope
The ingredient that stops a concentrated liquid separating in the bottle. It cleans nothing and without it there is no product.
In detail
A hydrotrope is a small, highly water-soluble molecule added to keep a concentrated formulation as one clear liquid. Surfactants, solvents, fragrance and water do not necessarily stay mixed at high concentration or at low temperature, and a product that separates on a cold shelf or gels in the bottle is a failed product regardless of how well its actives work. Hydrotropes solve that by sitting between the components and holding them in solution. They are why a concentrated liquid detergent can be poured at all, and why the same formulation at the same strength would be a cloudy sludge without them. They belong to a group of ingredients that is easy to overlook: present in meaningful amounts, doing nothing to the soil, and essential to the thing existing.
Why
- Hydrotrope is explained by Solubility and polarity
Sources for this page
Sources
Safer Chemical Ingredients List — functional-use classes
United States Environmental Protection Agency (EPA), Safer Choice · Government or regulator
Relied on for: That processing aids and additives are among the functional-use classes in which cleaning-product ingredients are assessed. (inferred from the source; not stated directly)
Handbook of Detergents (Surfactant Science Series)
CRC Press / Taylor & Francis · Reference work
Relied on for: That hydrotropes are added to concentrated liquid formulations to maintain a single homogeneous phase and prevent separation or gelling. (background and mechanism only)