Red precipitate, when well prepared, is in the form of fine powder or
small, brilliant, heavy scales of a scarlet or orange colour. It
consists of 101 mercury and 8 oxygen. It is insoluble in water.
It is easily distinguished from all other substances by the action of
heat. If a little of it is heated in a small glass tube, it becomes dark
brown, and on cooling recovers its original colour. But if the heat be
raised higher, metallic globules are sublimed, and oxygen gas is
disengaged. The escape of oxygen may be ascertained by plunging to the
bottom a small bit of burning wood, when the combustion will be observed
to be enlivened.