26o jidditional Remarks on Galvanic EkBricily, 



of communication, a very rapid produflion of gas took place from the wire conne£led with 

 the filver extremity of the machine, although but little or none cfcaped from the zinc 

 wire during the whole proccfs. 



After fome time a quantity of greyilh flacks, evidently metallic filver, were feparated by 

 the wire which gave out the gas, and a dark grey powder was depofited on the zinc wire ; 

 at this period of the procefs much lefs gas was difengaged, although a confiderable quantity 

 ftill appeared at the filver wire. After fome hours the apparatus was removed; at this 

 time a very confiderable quantity of metallic filver was depofited, and the zinc wire was 

 encrufted with a blueifli black fubftance. On endeavouring to remove this crufl: with the 

 finger part of it exploded, although flill moift : the wire was found to be very much cor- 

 roded, and full of holes. Next morning the powder which adhered to the wire being dry, 

 was touched with a knife, when it exploded again, with a very confiderable noife. There 

 can be little doubt, that thefe explofions proceeded from the fulminating filver of Ber- 

 tholet, which muft have been formed at the zinc wire ; indeed fome effeO: of this kind 

 was expedled. This experiment was repeated, and inftead of a folution of filver nothing 

 but pure ammonia was introduced into the tube, which anfwered equally well ; for the 

 filver of the zinc wire after being corroded, &c. was immediately taken up by the Vol. 

 Alkali, and afterwards depofited in its metallic form by the filver wire. A fmall quantity 

 of a fulminating fubftance likewife adhered to the zinc wire; and the fluid furrounding it, 

 being poured into a wine glafs, depofited after ftanding for fome time, a black ihining 

 film, which when dried, detonated like Bertholet's powder, and refembled it in all 

 refpefls. 



Another tube containing pure ammonia had copper wires introduced into it; after this 

 had been fubmltted to the a£lion of the machine for fome time, the fluid furrounding the 

 zinc wire aflumed a fine blue colour from diflblved copper, and the filver wire began to 

 depofit metallic copper ; this procefs continued for feveral hours, when a confiderable 

 quantity of very pure metal was precipitated; the blue colour of the fluid, however, never 

 extended fo high as the end of the filver wire, for as faft as it afcended,,the metal was imme- 

 diately thrown down in its metallic form, by this wire. I next filled the tube with an ammo- 

 niacal folution of copper, and employed copper wires. In a very fliort time after this had 

 been expofed to the a£tion of the machine, the upper part of the fluid in contaft with the 

 filver wire, became confiderably paler, and copper was precipitated ; in about an hour the 

 whole of the fluid in this part of the tube became as colourlefs as diftilled water, fo com- 

 pletely had the metal been precipitated. The precipitated metal was alfo the pureft I had 

 ever feen. From thefe experiments it would appear, that the galvanic influence might be 

 employed with fuccefs in the analyfis of minerals, more particularly in feparating lead, 

 copper, and filver, from their different folutions ; a very fmall quantity of a metal may 

 likewife be dete£led in this way, as I have found from dire£l trial. Before I finilh thefe 

 obfervations on ammonia and ammoniacal folutions, I fhall give the refult of one experi- 

 ment, where the vol. alkali itfplf was decompofed. 



4 Aquantit7 



