PYROPHORUS. An artificial product, which takes fire on exposure to the air. It is prepared by several methods. Four or five parts of burnt alum aro mingled with two of charcoal powder. The mix ture is introduced into a vial or matrass. The vial is filled two-thirds, and put in to a crucible. The body of the flask is also surrounded with sand, after which the crucible is put into a furnace, and surrounded with red-hot coals. The fire is gradually increased until the flask be comes red-hot, at which temperature it is maintained for about a quarter of an hour. As soon as the vessel is cool enough to be handled, it is taken out of the sand, and the contents transferred in to a dry glass, made warm, which must be secured with a glass stopper. When ever this mixture is poured out in the air, it takes fire.
A pyrophorns may be prepared by mix ing three parts of alum with one of wheat flour, and calcining them in a vial, as in the above case.
Tartrate of lead, also on being heated in a glass tube until it becomes converted into coaly matter, gives rise to a beauti ful pyrophorns.
The pyrophorus, invented by Doctor Hare, is formed from heating a mixture of three parts lampblack, four calcined alum and eight peariashes, in a gun-bar rel. The mixture is maintained at a cherry-red heat about one hour, or until it ceases to give off inflammable gas at the orifice of the tube, after which it is withdrawn from the furnace, and closely corked from the air. When cold, if pour ed from the gun-barrel into the air, it immediately glows and takes fire : and more especially if breathed upon, or slightly moistened. This pyrophorns may be preserved in its full activity for a year or more, if well corked up from the air.