Intelligence and Miscellaneous Articles. 237 



5. Basic chloride, in microscopic crystals, disseminated here and 

 there throughout the whole product. 



6. Sulphuret of copper, black, without any appearance of cry- 

 stallization. 



The whole of these substances covering the piece of galena, gave 

 it the appearance of a specimen from a mineral vein. 



In some of the vessels there were formed only chloride and chloro- 

 sulphate of lead, in others chloride and sulphate, which depended no 

 doubt upon the proportions of the sulphate of copper and of chloride 

 of sodium, and the density of the solutions. A voltaic couple, formed 

 of a piece of galena surrounded by a platinum wire, placed in a satu- 

 rated solution of common salt and sulphate of copper diluted with 

 3 vols, of water, gave rise to the formation of a considerable quan- 

 tity of crystallized chloride of lead in cubes, without any other pro- 

 duct ; they were similarly deposited, though a little larger, upon a 

 fragment of malachite which was placed in the solution. 



There is no evidence in opposition to the opinion that these reac- 

 tions take place in nature. In fact, the pluvial waters which reach 

 the mineral masses and veins, formed of metallic combinations, be- 

 come charged with chloride of sodium and sulphate of copper, arising 

 from the decomposition of the cupreous pyrites ; the resulting solu- 

 tions, once in contact with the galena, react upon it weakly, and 

 give rise to the various compounds described above. 



Two other compounds have been obtained, PbO,C0 2 and CaO.CO, 

 by the following processes : — Into a saturated solution of carbonate 

 of soda and carbonate of copper was introduced a plate of lead, 4 cen- 

 time by 2, surrounded by a platinum wire, the whole placed in a glass 

 vessel imperfectly closed, and left to spontaneous action forseven years. 

 The lead gradually oxidized at the expense of the atmosphere ; the 

 oxide formed, slightly soluble in water, reacted upon the carbonate 

 of copper, whence resulted hydrated oxide of copper and carbonate 

 of lead (PbO,CO-). This was in very small crystals, covering the 

 plate of lead, and their form appeared the same as the natural car- 

 bonate. The carbonate of lime was obtained by effecting the de- 

 composition of the sulphate of that base, a salt slightly soluble in 

 water, and naturally abundant, by a solution of bicarbonate of soda, 

 a compound found in several mineral waters. A plate of Montmartre 

 gypsum was introduced into the solution (saturated or not)of the latter 

 salt ; it soon lost its vitreous brilliancy, and was covered with small 

 rhombohedrons of carbonate of lime. At the moment of contact, 

 the gypsum dissolved, and reacted immediately upon the bicarbonate 

 of soda. There was a separation of carbonic acid, which partly re- 

 mained in the solution on account of imperfect closeness of the 

 vi MM I. The formation of sulphate of soda and carbonate of lime in 

 such a way that the plates which successively separated from the 

 gypsum were formed of small attached rhombohedrons, cannot be 

 ■opposed as solely owing to a double decomposition. It is probable 

 that the dissolving action of the carbonic acid plays a part in the 

 phenomenon. These effects always present themselves with weak 

 solutions of bicarbonate. 



These facts prove two principles, by the aid of which a certain 



