Borax Decahydrate is sodium borate purified form in nature. This mild, alkaline salt, which is white and crystalline and has excellent buffering and fluxing capabilities, is made up of boric oxide (B2O3), sodium oxide, and water. Borax decahydrate, which comes in granular or powder form, is a crucial supply of B2O3 for a variety of processes, especially those where the coexistence of salt is advantageous.