Sodium tetraborate

Sodium tetraborate (CAS 1330-43-4), also known by its E-number E285, is the anhydrous form of borax — a mineral salt used across industrial and food-contact applications as a preservative and buffering agent.

It also functions as a flame retardant and cleaning booster. Its anhydrous form offers a higher boron content and lower moisture contribution compared to hydrated grades, which matters for formulators managing water activity.

In building and construction, it is applied to wood treatments and insulation materials to provide flame retardancy and resistance to fungal degradation. Textile and leather processors use it in bath formulations to control pH.

This chemical helps improve the uptake of dyes and finishing agents. Water treatment operations rely on it as a buffering compound to stabilize pH in industrial process water, ensuring consistent chemical reactions.

At permitted levels under the E285 designation, it functions as a preservative in certain food contact and packaging applications in regulated markets. Sodium tetraborate anhydrous is supplied as a white powder.

It is also available as fine granules. Standard commercial grades include technical and food-grade specifications, with purity typically at 99% or higher. Packaging ranges from 25 kg bags to bulk quantities.