In this, then, we have a probable cause of the explosions occurring in
the powder works; but the explanation of the formation of the substance
is wanting, as potassium nitrate was shown not to give an explosive
substance with tin. A thin layer of a mixture of sulphur and potassium
nitrate was placed between sheets of tin and copper foil, and allowed to
stand, being kept constantly moist. After a time the copper was found to
have become coated with sulphide, while the tin was largely converted
into the explosive basic nitrate. The conditions are obviously the same
as those found in the powder machinery, where bronze and tin solder are
constantly in contact with moist gunpowder. The chemical action is
probably this: the sulphur of the powder forms, with the copper of the
bronze, copper sulphide; this is oxidized to sulphate, which reacts with
the niter of the powder, forming potassium sulphate and copper nitrate;
the latter, as shown above, then forms with the tin of the solder the
explosive basic nitrate, which, being insoluble, gradually collects in
the joints, and finally leads to an explosion.--_Journal für Praktische
Chemie._

* * * * *




METALLIC THORIUM.

By L.F. NILSON.


The density of thorium as obtained by reducing the anhydrous chloride by
means of sodium was found by Chydenius, 7.657 to 7.795. The author has