TgJ Jer2:22 :אֲרֵי אִם תְדַמַן לְאִתנַקָאָה מֵחוֹבַך כְמָא דִמנַקַן בְנִתרָא וֻמחַוְרִין בְבוֹרִיתָא‏ : for should you think to cleanse yourself from your sin as one launders with nitre and whitens with lye
See the entire entry for nqy vb. D to cleanse

TgJ Jer2:22 :
See the entire entry for nṯar, neṯrā n.m. natron