M. Boussingault has remarked a singlar deficiency in the [p226] specific gravity of the native alloys of gold and silver when compared with calculation, or with the results obtained from an alloy similar in composition prepared by fusion; thus the native gold of Marmato has a specific gravity of 12.666, whereas, by calculation, it ought to be 16.931. The gold of Malpaso, by experiment, is 14.706, by calculation, 18.223, and by fusion, 18.1. The gold of Santa Rosa, by experiment, is 14.149, and by calculation, 16.175. This difference, M. Boussingault says, is not due to porosity in the native gold, as he has observed it in the granular and fine varieties, but a peculiar character of the metal in this state. Such an enormous difference, however, is one that can be admitted only upon repeated experimental proofs, made in the most unexceptionable manner; and, considering that it is only in some of the metals that any permanent difference in specific gravity can be established, and even with them to but a small extent, would be a fact so important as to be worth extreme trouble in the verification.—Annales de Chimie, xxxiv. 408.
8. Prothéeïte—a new Mineral.
9. Volcanic Bisulphuret of Copper.
M. Covelli descended into the crater, until within 300 feet of the edge of the large eastern opening, from which the great current of lava flowed in 1822. Here the fumeroles presented the most beautiful crystallizations of sulphate of lime and sulphur. On examining the scoria they were found incrusted and covered with a substance, having all the shades of colour belonging to blue, green, and black. Sometimes it resembled a spider’s web in appearance, sometimes soot deposited in the cavities of the scoria. Many specimens were collected, and also a portion of water condensed from the vapours which issued forth, and which evidently contained sulphuretted hydrogen and muriatic acid. The temperature of the vapour was as high as 85° C., in some places, and even up to 90°, at half a foot beneath the surface.
The water being examined was found to contain only a little sulphuretted hydrogen, and a little muriatic acid. The black substance was soon ascertained to be a pure sulphuret of copper. Being analyzed, 100 parts yielded 32 parts of sulphur, and 66 of copper, a loss of two parts being incurred, which accords very nearly with the composition of the bi-sulphuret of copper. The blue and bluish-green substances were found to be mixtures of this sulphuret with sulphate and hydro-sulphuret of copper.
M. Covelli concludes that this substance has been formed by the action of sulphuretted hydrogen on the sulphate and muriate of copper evolved by these fumeroles; and observes, that its composition accords with such an opinion, the deutoxide being that which forms the Vesuvian cupreous salts.—Ann. de Chimie, xxxv. 105.