In metallurgy, refining consists of purifying an impure metal. Depending on purity, benzalkonium chloride ranges from colourless to a pale yellow (impure). For religious purposes, it was ritually "impure" ("vinum spurcum"). Pyridine is colorless, but older or impure samples can appear yellow. Saint Jerome claims Jews were possessed by an impure spirit. It may be caused by impure distillation. Brahman is Nirguna in the sense that impure qualities do not touch it. The Puranas speak of many of these tribes as foreigners and impure barbarians (Mlecchas). The Marangoni effect depends on the liquid that is foaming being impure. Any product of an impure or improperly slaughtered animal is also non-kosher. Yiska refused her as a sacrifice as she was "impure", or not a virgin. Everyone drank ale or cider as water was often too impure to drink. Kabbalah distinguishes between two realms in qlippot, the completely impure and the intermediate. Certain activities are prohibited as a result of acquiring this "impure" status. She stops eating and interacting with the other novices and nuns over her "impure thoughts".