Acids of every denomination are unfriendly to the teeth; and by frequent use will destroy the enamel; the following mixture not only whitens, but tends to preserve them. Take Peruvian bark, 2 oz. charcoal, half an oz. Armenian bole, 1 oz. mix them altogether in a mortar. If the teeth are washed, take a piece of wood like a butcher’s skewer, made soft at the end, cover it with linen, dip it them in the above ponder, and apply it to the decayed part.