Like ?????n? ?n other f?rm?, ?r??k r??k ??t? ?? a l???l ?n??th?t??, numbing th? tongue or m?uth only where by d?r??tl? ?l???d. Pur?r varieties ?f ?r??k w?ll sink in w?t?r ?r m?lt at th? ?dg?? when n??r a flame (?r??k vaporizes at 90 °C, 194 °F).Cr??k ?????n? as ??ld on the streets might b? adulterated or “?ut” w?th other substances m?m??k?ng