Intelligence and Miscellaneous Articles. 77 



with much water, decomposes after a certain time ; it becomes black, 

 and eventually consists entirely of finely divided mercury, the su- 

 pernatant liquor containing arsenious and hydrochloric acids. 



This decomposition is perfectly analogous to that v/hich water 

 effects in the precipitate formed by phosphuretted hydrogen in the 

 solutions of bichloride of mercury, this precipitate changing into 

 mercury, phosphorous and hydrochloric acids. This decomposition 

 occurs more rapidly than that with the arsenical compound. 



Both precipitates undergo similar changes by the action of nitric 

 acid ; by the aid of a gentle heat they are converted into protochlo- 

 ride of mercury, and the arsenic and phosphorus are at the same 

 time oxidized. 



This similar reaction seems to indicate also a similaritj'' of com- 

 position, and this is confirmed by analysis ; the arsenical precipi- 

 tate, according to M. Rose, is represented by As- Hg^ + 3 Hg Cl'^. 



The phosphuretted precipitate differs from the above only in con- 

 taining three atoms of water, whereas the arsenical one is anhydrous. 

 These two precipitates also differ in the mode in which they are 

 acted upon by heat ; the chloro-phosphuret of mercury contains ex- 

 actly so much water that its hydrogen converts all the chlorine into 

 hydrochloric acid, and its oxygen all the phosphorus into phospho- 

 rous acid. The chloro-arseniuret of mercury, on the contrary, does 

 not yield any gaseous product under the same circumstances ; it 

 sublimes without any residue, decomposing into protochloride of 

 mercury and metallic arsenic. There sublimes, at the same time, 

 a small quantity of a reddish substance which consists of mercury, 

 chlorine and arsenic, and which is probably merely the substance sub- 

 limed without decomposition. Sometimes the sublimate contains a 

 little metallic mercury. The analysis of the arsenical precipitate 

 and its action on water fully confirm the composition of arseniuretted 

 hydrogen as stated by MM. Dumas and Soubeiran. 



The precipitate formed by antimoniuretted hydrogen gas, in the 

 solution of bichloride of mercury, differs from both the preceding 

 in composition. — Ann. de Chim. et de Phys., Juillet 1841. 



NATIVE BROMIDE OF .SILVER, AND ANALYSES. 



M. Berthier says, that in the district of Plateros, seventeen leagues 

 from Zacatecas in Mexico, silver ore is found in two different 

 states : first, native silver ; and secondly and principally in a state of 

 combination in small olive-green or yellowish crystals, supposed to 

 be chloride, but which he found to be bromide of silver. According 

 to M. Diiport, from whom M. Berthier received these specimens, 

 this substance is not rare in Mexico, but occurs frequently in fine 

 cubic and octahedral crystals. 



Tlic si)ecimen examined by M. Berthier was from San Onofe. It 

 was compact, of a slightly reddish gray colour ; fracture uneven ; 

 splendent ; penetrated with small cavities, some of which were par- 

 tially filled with a substance of a dull pale yellow colour, and which 

 the miners call oxide of lead ; other cavities contain very small im- 



