■ On the Chemical Properties attributed to Light. 453 



vr. 



An Inquiry concerning the Chemical Properties that have been attributed to Light. Bf 

 Benjamin, Count of Rumford, F. R. S. AL R. L J. 



H, 



(Concluded from prfgc 405.) 



. AVING been fo fuccefsful in my attempts to reduce the oxide of gold, by means of 

 charcoal, in the moijl ivay^ 1 lod no time In making fimilar experiments with the oxide of 

 filver. 



Experiment No. 11. A folution of fine filver, In ftrong nitrous acid, was evaporated by 

 drynefs, and the refiduum re-difTolved in diftilled water. 



A portion of this foiution (which was perfeftly colourlefs), diluted with twice as much 

 diftilled water, was poured into a phial containing a number of fmall pieces of charcoal j 

 and the phial, being well clofed with a new cork ftopple, was expofed to the a£lIon of the 

 fun's rays. 



In lefs than an hour fmall fpecks of revived filver began to make their appearance on the 

 furface of the charcoal ; and, at the end of two hours, thefe fpecks became very nume- 

 rous, a^.d had increafed fo much'in fize, that they were diflindly vifible to the naked eye 

 at the diftance of more than three feet. They were very white, and poflelTed the metallic 

 fplendour of filver in fo high a degree, that when enlightened by the fun's beams their luflre 

 was nearly equal to that of very fmall diamonds. 



The phial, which was in the form of a pear, and about i^ inch in diameter at its bulb, 

 was very thin, and made of very fine colourlefs glafs \ the aqueous folution was alfo per- 

 feftly tranfparent and colourlefs ; and, when the contents of the phial were illuminated by 

 the diredt rays of a bright fun, the contrail of the white colour of thefe little metallic fpan- 

 gles with the black charcoal to which they were fi.xed, and their extreme brilliancy,, aiForded 

 a very beautiful and interefting fight. 



As the air had been previously expelled from the charcoal by boiling it in diftilled water, 

 it was fpecifically heavier than the aqueous folution of the metallic oxide, and confequently 

 remained at the bottom of the bottle. 



Experiment No. 12. A phial as nearly as pofirble like that ufcd in the laft experiment, 

 and containing the fame quantity of diluted aqueous folution of nitrate of filver, and alfo 

 of charcoal, was inclofed in a cylindrical tin box, and expofed one hour to the heat of 

 boiling water in an apparatus ufed for boiling potatoes in Ream for the table. 



The refult of this experiment was uncommonly ftrlking : the furface of the charcoal was 

 covered with a mod beautiful metallic vegetation ; fmall filaments of revived filver, refem 

 bling fine flatted filver wire, pufliing out from its furface in all dire£lions ! 



Some of thefe metallic filaments were above one-tenth of an inch in length. On agitat- 

 ing the contents of the phial, they were eafily detached from the furface of the charcoal, to 

 which they feemed to adhere but very flightly. 



Thefe experiments were repeated feveral times, and always with precifely the fame re- 

 fults. 



When the oxide of gold was reduced In this way, the revived metal appeared under the 



form of fmall fcales, adhering firmly to the furface of the charcoal. May not the difference 



Vol. II. — Jan. 1799. 3 N .of 



