Nedo Arsenical Copper, 217 



strongly heated, so much so that it is necessary to surround the re- 

 ceiver with cold water to prevent the reconversion of it into carbon- 

 ate of potash. Tlie saturation is complete when it ceases to give 

 out heat. It is then dissolved in the smallest possible quantity of 

 water at the temperature of 100° to 120° Fahr.; upon the cooling of 

 the filtered solution, the greater part of the bicarbonate separates in 

 fine crystals. — Poggendorffs Annals. 



NEW LOCALITY OF ARSENICAL COPPER IN CHILI, BY 

 VON ZINKEN. 

 Amongst some Chilian minerals from San Antonib, near Copiapo, 

 was some massive native silver, accompanied by a tin-white substance, 

 which, when broken, has somewhat the appearance of copper py- 

 rites ; this locality also furnishes native copper, native silver con- 

 taining copper, polybarite, and calcareous spar. The fracture of this 

 new mineral is uneven ; it occurs tabular, kidney-shaped, and mas- 

 sive ; it scratches calcareous spar, but is scratched by fluor spar and 

 a knife ; its specific gravity is not easily determined, as it is always 

 accompanied by native silver. Exposed to heat in an open tube, it 

 gives out arsenious acid, then a white vapour, (oxide of antimony ?) ; 

 upon increasing the heat it is converted into a red scoriaceous mass, 

 which attacks the glass, and imparts to it the colour of oxide of cop- 

 per ; the fumes also smell of sulphureous acid. The roasted mineral 

 fused with soda gives a button of copper not containing silver. 

 Melted with borax, it gives a red and yellow scoriaceous mass, 

 and a bead of copper. It is acted upon violently by nitric acid, 

 which dissolves it, leaving a black flocculent residue recognisable as 

 sulphur, mixed with a little arsenic. This mineral is therefore a 

 compound of arsenic, sulphur, antimony, and copper, and is somewhat 

 similar to condurrite, an arsenical copper found at Condurrow, near 

 Camborne, Cornwall. — Poggendorff's Annals, vol. 41, p. 392. 



DEFINITE COMBINATION OF OXIDE OF SILVER AND 

 OXIDE OF LEAD, BY PROF. WCEHLER. 



When a salt of silver is contained in a solution of a salt of lead, 

 caustic alkali throws down a yellow precipitate, — a reaction which 

 is of great interest in analytical chemistry. This yellow precipitate 

 is insoluble in excess of caustic alkali ; but by digestion in the latter, 

 any free oxide of lead precipitated with it may be separated. This 

 yellow substance, according to analysis, is a combination of 1 equiva- 

 lent of oxide of silver, and 2 equivalents of oxide of lead ; and 100 

 parts consist of 34*23 oxide of silver, and 65*77 oxide of lead. Upon 

 exposure to the light it turns black. Upon heating to redness it gives 

 a mixture of metallic silver and oxide of lead. In hydrogen gas it is 

 reduced to an alloy with a very gentle heat. It is easily soluble in 

 nitric acid. 



In a mixture of a salt of silver with a salt of protoxide of manga- 

 nese, a caustic alkali throws down a black precipitate. This appears 

 to be a very intimate mixture of metallic silver with peroxide of manga- 

 nese. It is dissolved by acids without ihe disengagement of any gas 



