ly Zinc in the metallic State. 361 



therefore fubftituted for tbefe threads a piece of brafs wire 

 which appeared to nic to unite all the necelfary conditions, 

 both on account of its ftrcngih, and the property it has as 

 containinof zinc to exercife its attraftion on the acetite of 

 lead. A Tecond inconvenience arifes in ftriiSlIy following the 

 procefs above dcfcribed. It often happens, when the fize of 

 the piece of zinc is too large, or when the veflel is not ex- 

 artly of the proper form, that the decompofition lakes place 

 with great rapidity ; each molecula of the new metal proceeds 

 immediately to the zinc, adheres to it in a confufed manner, 

 and at the end of two or three days, and fometimes of twentv- 

 cfour hours, the crvftallized portion fuddenly detaches itfelf 

 and is precipitated to the bottom of the vefll-l to give place to 

 a new crvdaliization. The procefs is then divided into fe- 

 veral periods, which appears to be a matter of indifference ia 

 a chemical point of view, bat greatly leflens the intereft ex- 

 cited by this curious experiment. 



I obviated this inconvenience by fixing, in a perpendicular 

 direftion, to the lower part of the piece of zinc, the fame 

 brafs wires twirted into a fpiral form, and difpofed in fach a 

 manner as to be about three centimetres dillant from the 

 bottom of the veflel. 



By adopting this modification, as each molecila of the 

 zinc formed a portion of the brafs, the furface of which was 

 in contact with the faturalion, it became covered with a 

 great number of fmall, brilliant, metallic laminae, difpofed at 

 firft alternately and horizontally, and then eroding each other 

 in every direftion *. 



When it is required that the brafs, though covered with 

 metal, (hould retain the forms it has firft acquired, it will be 

 proper to diminifh the quantity of the acetite of lead. 



About fix months ago, T repeated this experiment with 

 common and with dillilled water, in order that I might exa- 

 mine the products. The refult of this examination is as fol- 

 lows : ,< 



Having felefted two glafs jars of equal capacity, T intro- 

 duced into each four decagrammes of very pure cryftallized 

 acetite of lead. 



The two vefli-ls having been marked No.T. and II., I 

 poured into the firft 54 decagrammes of conimon water, and 

 as much ddiillcd water into the fecond. Thefc quantities 



" The configuration of tliefe laminae is fulijeft to an infinite variety, 

 which ftems to depend, ift, On the form and iliffcrcnt ilimcnfions of the 

 Veflel in which the experiment is perfonnod : id, And perhaps alfo on 

 rrj^iilar quantities of the zinc and acetite of lead employed. I have Ibcii 

 the laminae (omerimes circular, foir.etinies hexagonal, and fometimes alfo 

 affecting the fi^'urc of a leaf ©f fern or of ouk. 



were 



