Sodium Phosphate

Sodium phosphate is a sodium salt of phosphoric acid, which actually makes it a weak base. On the pH scale, a base has a pH above between 7.0 and 14.0 and, therefore, can be used as a pH adjuster. Sodium phosphate, being a base, will adjust the pH upward. This is useful in many cases, including buffering water-based systems and activating thickening agents, such as hydroxyethylcellulose.

Another case where this is important is in mineral-based sunscreens that contain zinc oxide. Acidic, or low, pH levels will dissolve the zinc oxide and leave the sunscreen ineffective. Using sodium phosphate to increase the pH of the product will prevent this degradation of zinc oxide.