STERINEA.
175
This mineral has not been analyzed. It is, probably, a nearly pure Sulphate ofAmmonia. It dissolves readily in water.
It occurs about volcanoes, in the fissures of the lava; more particularly at Etna ,Vesuvius , and the Lipari Isles.
APHTHITALITE. Picralum Vesuvian-um.
148. Primary form of artificial crystals, right rhombic prisms;M:M=112°8', a \a= 106° 46'. It has been observed in natureonly in a massive state, presenting imperfectly mammillary forms,which are sometimes composed of concentric coats.
H.=2—3. G.=1-731. Lustre vitreous. Color white, sometimestinged with blue or green. Translucent. Taste saline and bitter,disagreeable.
It fuses readily before the blowpipe, without intumescence. It effervesces stronglywith sulphuric acid.
Obs. Its only known locality is Vesuvius , where it occurs upon the lava in masses,often an inch or more in thickness.
SAL-AMMONIAC. Picralum octahedrum.
Octahedral Ammoniac Salt, A/. Muriate of Ammonia, P. Xaturliclier Salmiak, W. Salmiak, L.Aiumoniaque Muriat6e, H.
149. Primary form: the regular octahedron. Secondaries:figs. 1 and 1(3, PI. I. Cleavage parallel with the faces of the octa-hedron. Imperfect crystallizations: stalactitic and globularmasses ; in crusts, or as an efflorescence.
H.=l-5—2. G.=1-528. Lustre vitreous. Streak white. Colorwhite; often yellowish or greyish. Translucent—opaque. Frac-ture conchoidal. Taste saline and pungent.
According to Klaproth , it contains
Muriate of Ammonia 99 5 97 50
Sulphate of Ammonia 0-5 2-50
It dissolves readily in about three times its weight of water ; but does not deli-quesce. It is completely volatile before the blowpipe, rising in white fumes. Min-gled in the pulverized state with quicklime, it gives out the pungent odor of am-monia.
Obs. It occurs in the cracks and fissures of volcanoes, particularly at Etna , theisland of Vulcano and Vesuvius . It has been observed in small quantities in thevicinity of ignited coal seams, as at St. Etienne , in France , and also at Newcastle,and in Scotland . It occurs also in Bucharia .
Sal ammoniac has not hitherto been found in nature in sufficient quantities to beobtained for commerce. It is a valuable article in medicine. It is employed by tin-men to prevent the oxydation of metallic surfaces, undergoing the operation of tin-ning or soldering.
The d/i/juwa.Jt, sal-ammoniac of Dioscorides , Celsus , and Pliny , is fullyprovedby Beckmann, (Hist, of Inventions, IV, 360.) to be common rock salt. It is describedby Pliny as a native salt, dug in Egypt , near the oracle of Ammon, whence its name jthis name was afterwards transferred to the muriate of ammonia, when, subsequently,