PROOFS OP THE PROPERTIES OF ALUMINE.

201

Remark. ..This experiment proves that there exists a strongaffinity between silex and alumine. Guyton de Morveau hasbeen deceived in every instance of the affinities, which he at-tributes to the earths upon each other,* excepting in this casewhich has been observed before him by Chenevix.f He has at-tributed phenomena to substances which do not partake of it,but which resulted from the impurities of his re-agents.

Experiment IV,

Alumine, sulphur and charcoalform a compound which takafre spontaneously in atmospheric air,

(Preparation of pyrophorus.)

> In order to prepare pyrophorus, equal parts of powderedalum and brown sugar are melted over the fire, and are keptstirring, till reduced to dryness. The mixture is then to be finelypowdered, and introduced into a common phial, coated with clay,to which a glass tube, open at each end, is luted, to allow theescape of the gases that are produced. The phial must then beset in the fire, surrounded by sand, in a crucible. Gas will issuefrom the open end of the tube, and may be inflamed by a lightedpaper. When this ceases to escape, the crucible may be removedfrom the fire; and a little moist clay pressed down upon theopen end of the tube, to prevent the access of air to the contentsof the phial.

The pyrophorus thus formed is a black and very light powder,which instantly takes fire, when poured out of the bottle into the-air; and inflames vividly in oxigen gas.

Rationale. ..The accension of pyrophorus is thus accountedfor by Gren.J Part of the charcoal decomposes in a red heatpart of the sulphuric acid of the sulphate of alumine, and becomes

* Ann- de Chem. XXXI. + Philosoph. Trans. May, 1802.

} Cren’s Principles of Chemistry, vol, I. p. 256.