184 Chemical Noticgsj 



falls already known, are the clc(Slrat of copper^ which is of a 

 beautiful green colour; the eleftrat of zinc, which is of a 

 dark gray; that of iron, which has a rcddifli-yellovv colour; 

 and the beautiful ele6trat of filver, which cryftallifes in re- 

 gular and exceedingly tranfparfcnt dodecaedra. Thefe me-' 

 'tallic ele6:rats are infoluble in water. They, however, can 

 be earried in the clc6lric current to a confiderable diftance,' 

 ^nd cover other metals with their falinc coatincr. Hitherto 

 the c'Tec^rat of filvcr is that which has exhibited the greateft 

 conftancy and regularity in its cryftallifation : it depofits'itfelf 

 on'condu<f^ors of gold and filver, on glafs^ . an^ other bodies^ 

 with which it is in conta6l. •' '-■"-'•'^ -'■'■' 



/' Brugnatelli has endeavoured to determine the'pro'periiiest 

 rtPtiiefe metallic cryftals : he has found that they are iiifipld;- 

 that they are Infoluble in water, and that they efflorefce' 

 in an Satmofphere of a high temperature. The nitric acid 

 diffolves them with a ftrong efFen'efcence. The folution is 

 rmipid, but alkalies render it turbid and decompofcit. There 

 is precipitated from it an oxyd of filvcr, which can be attacked- 

 bv all the acids. The eras difenjrajred durins; the effcrvefcence 

 has not yet been examined, but it is fuppofed to be of a pe- 

 caliar nature. 



'' Gold and platina are not fenfiblv altered bv the eleftric 

 matter which pafTes through them ; though it often happens 

 that the electric current depofits on gold a fi;ratum of zinc^, 

 copi^er, mercur>^, or filver, according to whichever of thefe 

 metallic bodies it traverfes. 



*' Some are difpofed to believe that the eleclric matter 

 poficfles the property of conveying at the fame time two 

 metals through a third body. If the tongue, indeed, be 

 touched in two different points with different metals, twf> 

 pieces of coin for example, one of gold and the other of filver ; 

 and if the upper edge of each of thefe pieces be brought into 

 o6nta6l fo as to form an arc, aflrorig favour will be perceived; 

 and the nature of this favour will be different accordino* to 

 the diverfity and combination of the metals; which evidently 

 appears to indicnie an aflbciation of the fubfi^ances. 



^^ To conclude : The difcovery of Volta is ftill in its in- 

 : as yet we have only a fmall number of fa6ts, and 



prudence 



