Intelligaice afid Miscellaneous Articles. 227 



In a memoir which M. Becquerel has read to the Academy, he has 

 given an account of experiments upon the crystallized metallic sul- 

 phurets, beginning with that of silver. The apparatus employed con- 

 sisted of two glass tubes, the lower part of which was filled with 

 very fine clav slightly moistened, with a fluid conductor ot electricity. 

 In the upper part were poured the fluids, the reaction of which upon 

 each other and upon the plate of metal, one end of which was placed 

 in each of them, occasioned the electrical eff"ects requisite to produce 

 the compounds. The two tubes were placed in another which con- 

 tained a fluid to establish a communication between them. In order 

 to obtain the sulphuret of silver, a saturated solution of nitrate of 

 silver is put into one of the tubes, and a saturated solution of hydro- 

 sulphuret of potash in the other, and the ends of a plate of silver is 

 placed in botli of them. That which is in contact with the nitrate, is 

 soon covered with metallic silver ; whilst at the other, which is the po- 

 sitive pole, water and sulphuret of silver are formed, and the latter 

 combines with the sulphuret of potassium. This double sulphuret is 

 gradually decomposed by the action of the nitric acid, wliich takes 

 place slowly, because in chemical decompositions effected by electrical 

 forces of slight tension, the oxygen goes first alone to tlie positive 

 pole, and the acid follows afterwards. Sulphuret of potash is formed ; 

 the sulphuret of silver is developed and crystallized in beautiful small 

 octahedral crystals, the appearance of which resembles that of the 

 crystals of the same substance found in silver mines. 



The crystallization of the sulphuret of silver is owing to the very 

 slow decomposition of the double sulphuiet, which gives the mole- 

 cules time to effect the oscillatory motion necessary for similar faces 

 to react upon each other, according to the laws of crystallization. 



Sulphuret of copper perfectly resembling the natural compound 

 may be obtained by the same process. Oxysulphuret of antimony or 

 kermes is procured in small octahedral crystals of a deep brownish 

 red colour, and in laminae. As to the sulphurets of iron and zinc, 

 which decompose readily by the simultaneous action of air and water, 

 it is necessary to employ certain precautions to prevent this decom- 

 position. M. Becquerel has however succeeded in obtaining very 

 small cubic crystals of sulphuret of iron, of a yellow colour, resem- 

 bling that of pyrites. The iodides, the bromides, and crystallized 

 metallic seleniurets may be obtained by the same process. The io- 

 dide of lead is in brilliant yellow octahedral crystals j that of copper 

 has a similar form, but a difterent colour. 



M. Becquerel concludes from these results, that it is probable that 

 nature has adopted a similar process in forming natural sulphurets ; 

 and he explains how the phaenomena may operate at the instant of 

 the consolidation of the masses. — Le Globe, Nov. 4, 1829. 



Without in the slightest degree questioning the accuracy of the 

 above detailed experiments, I may be allowed ])erhaps to doubt 

 whether the inferences deduced from them are jjcrfectly correct j for 

 there are facts on record wiiich prove that sulphuret of iron, in cry- 

 stals, may be formed via humida. In the I'liil. Trans, for I79H, there 

 2 G 2 is 



