78 Intelligence and Miscellaneous Articles. 



■vnll thus be continually bathed by the movement of the liquid with- 

 out being inundated, so that the polarization will be suspended and 

 the bubbles of hydrogen will be freely disengaged through the in- 

 terstices between the particles ; besides which, the lower strata of 

 the acidulated water, in consequence of the pressure which they 

 have to support, will filter slowly through the cloth, which will not 

 be the case to any extent with the upper and middle strata. Now 

 these lower strata are precisely those which contain the sulphate of 

 zinc which it is necessary to eUminate. The result is an electric 

 current, which is perfectly constant until the entire disappearance of 

 the zinc, and which is obtained with no more care than that of keep- 

 ing the reservoir filled. 



My method of uniting a number of pairs is as follows : — The stone- 

 ware pots in which they are contained, which are 3 or 4 diameters 

 in length, and consequently have the appearance of tubes, are united 

 and cemented into a bundle or block, which is readily transported 

 from place to place. The upper surface being horizontal, small 

 gutters are employed to convey the acidulated water to each pot. 

 With this arrangement, by placing a second reser\'oir above the pile, 

 and altering the nature and elevation of the diaphragms, it is easy 

 to employ a second liquid, which may be made to fall directly drop 

 by drop on the grains of coke, such as nitric acid; — it may be 

 used with advantage when very weak, and when it will no longer 

 serve for the battery of Bunsen from its ceasing to absorb hydrogen. 

 The liquids on leaving the pots are collected and may continue to be 

 used until saturation. — Comptes Rendus, April 5, 1852, p. 533. 



ON THE PREPARATION OF PURE SILVER FROM CHLORIDE OF 

 SILVER. BY C. BRUNNER. 



It has long been known that pure silver for chemical purposes is 

 best prepared by the decomposition of chloride of silver. This de- 

 composition can be performed in various ways : Poggendorff * several 

 years ago described a process in which it was efiected by galvanism ; 

 this appears to me to be preferable to all others hitherto known, and 

 the one here described can only be regarded as a modification of it. 



Well-washed precipitated chloride of silver is to be put into a cup 

 of silver, platina or copper, the outer surface of which is covered with 

 wax, in such a manner that only a round space of one or two inches 

 in diameter, according to the size of the cup, remains uncovered. 

 On the bottom of a larger earthen cup a disc of amalgamated zinc 

 is to be laid, on the middle of which the cup containing the chloride 

 of silver is placed, in such a manner that the portion not covered with 

 wax may come in contact with the zinc. Water slightly acidulated 

 with sulphuric acid is now to be poured into the apparatus, until it 

 rises above the margin of the inner cup, so that this will be com- 

 pletely sunk in the water. The decomposition of the chloride of silver 

 immediately commences at the edge of the cup containing it, and pro- 

 ceeds inwards to the middle : this is readily known by the dark gray 

 coloiir assumed by the silver as it separates ; the decomposition will 

 be completed in from 24 to 48 hours ; its completion may be known 

 * Poggendorff's Annalen, vol. xxv. p. 342, 



