Exjxnments eft the Oxidation of Metah hy EkHricUjt I43 



EXPERIMENT XIV. 



Eight lengths of wire, of the fame diameter, was exploded in the receiver of fix inches 

 diameter; and after it had been in water five minutes, the mercury gage rofe 1^ of an' 

 Inch, which was a degree of diminution of about 2i cubic inches, and confequently not 

 agreeing with my former experiments. 



The refult of thefe two experiments occafioned feveral repetitions, and all nearly with 

 the fame refult ; but on repeating them in the winter, ■\^hen the temperature was low, I 

 found the refult as I firft had (namely) a diminution of air in the fmall receiver, and none 

 in the large one. It then occurred to me that the temperature muft have occafioned this 

 variation, and that putting the receiver in water for five minutes was, perhaps, not fuffi- 

 cient to bring the air in the infide of the receiver to its former temperature. I therefore 

 placed a thermometer in the infide of the large receiver, and by exploding one length of 

 wire, the temperature was raifed about two degrees; and when the receiver was fet in 

 water, the air did not return to its former temperature in lefs than twenty minutes; 

 confequently this pointed out to me one error, which I was not avi-are of; but it was not 

 fufficisnt to explain the whole, becaufe this only would indicate a diminution but lefs than 

 truth. By repeating the experiment at different times, I perceived that the firfl explofion 

 in a low temperature caufed the mercury to rife near two degrees, and that every fub- 

 fequent explofion affefted it lefs. After feven or eight explofions had been given, hardly 

 any rife in the mercury could be perceived. And alfo when the temperature was at about 

 60°, the firft explofion did not then caufe the mercury to rife to above i°, and it would 

 ceafe to rife after the third or fourth explofion; When the temperature was at about 70% 

 hardly any rife in the mercury could be perceived, even at the firft explofion ; this unfolded 

 the whole, becaufe it appeared that when the temperature was low, the explofions raifed 

 it fo much as to caufe an expanfion in the inclofed air, which kept up the preflure upon 

 the mercury in the gages, and of confequence hindered them from indicating any lofs ; , 

 and when the tensperature was high, the explofions did not caufe fuch expanfion, con- 

 fequently permitted the gages to indicate the true lofs, or quantity of air which had been 

 abforbed by the divided metal. 



I thought it proper to memion the above in full, not only for the advantage of fuch as 

 might undertake fuch experiments, but likewife to prevent wrong conclufions being drawn 

 from the refult of the firft fet of experiments with large receivers, as they have been fhewn 

 to many, and fome authors have brought them forward to fupport their own erroneous 

 notions. 



We may alfo conclude from the fa£ls that the difference of diameters of the receivers 



wherein leaden wire is exploded, neither favours, nor hinders, the diminution of the at- 



mofpherical air therein coiitained. If two leaden wires of equal lengths and diameters be 



exploded by equal eleftric difcharges, in unequal receivers, the diminution of the air 



Z which 



