ʻO ka soda caustic (i ʻike ʻia hoʻi ʻo sodium hydroxide) he kemika ʻoihana maʻalahi a hoʻohana nui ʻia i hoʻohana ʻia ma nā ʻano ʻoihana like ʻole e like me nā lole, pulp a me ka pepa, alumina, kopa a me nā detergents, ka hoʻomaʻemaʻe ʻaila a me ka mālama ʻana i ka wai. Kūʻai pinepine ʻia ia ma nā ʻano kino ʻelua: wai (alkali) a paʻa (flakes). ʻOi aku ka maʻalahi o ka lawe ʻana i nā flakes soda caustic ma nā wahi lōʻihi a ʻo ia ka huahana makemake ʻia no ka hoʻokuʻu aku. ʻO ka hui ka lua o ka mea hana soda caustic nui loa ma India me ka hiki ke hana i kēlā me kēia makahiki he 1 miliona tone.