144 Efcperimenis en the Oxidation of Metals by Ele5lricity. 



which they contain will be equal in both ; and if the receivers contain atmofpherical air, 

 that which is feemingly loft by the procefs is oxigen gas, abforbed by the exploded metal, 

 which becomes converted into a true metallic oxide. 



If it be required to colleft the produce for further inveftigation, a receiver of the largeft 

 diameter then becomes neceflary, becaufe the oxide is more perfeft, and a greater quan- 

 tity of powder can be produced, and the experiment oftener repeated, before the receiver 

 becomes opaque, which is the cafe when receivers of fmall diameters are ufed. 



The foregoing experiments upon lead, prove that a receiver of one inch diameter is 

 fufEcicntly wide, and therefore preferable to wider, becaufe when the tetnperature of the 

 air in the infide is raifed by the explofions, it is much fooner brought to its former tem- 

 perature, and is not fo liable to equivocal refults. ^ I have not, therefore, thought it proper 

 to relate the experiments which were made in wider receivers upon the following metals : 

 fuch receivers being neceflary only when a large quantity of oxide is required. 



EXPERIMENT XV. 



Tin. 



Sixteen inches of tin wire, of ^^o part of an inch in diameter, was put Into Fig. 4, and 

 after it had been laid in water fo long, that the air in the infide was become of the fame 

 temperature as the water itfelf ; It was afterwards exploded by two dlfcharges, and by that 

 means converted Into an Impalpable powder, nearly the fame as the lead wire, but of a 

 purer white. The apparatus was then again laid In water * till the air had gained its 

 former temperature ; when the cock was opened, the mercury rofe three inches, and the 

 air, by the teft of flame, feemed to be as as highly azotic as that in which lead had been 

 exploded In the ninth experiment. 



The laft experiment, repeated with wire of -^^ of an Inch diameter, and the rcfult wa» 

 the fame. 



Tin burns with a vivid yellow fl^me when exploded. 



EXPERIMENT XVI. 



Iron. 



Thirty-two Inches of Iron wire, of -^^ inch diameter, was put Into Fig. 4, and ex- 

 ploded by five dlfcharges : the mercury rofe three Inches. 



The wire was converted into an Impalpable powder, of a reddifh brown colour ; the 

 refidue of air feemed to be the fame as that left In the ninth and fifteenth experiments, 

 wherein lead and tin had been exploded. It extinguifhed a candle nine times. 



* The apparatus was always laid in water a fufficient time to cjufe the air in the infide to become of the 

 .fame temperature as the water, before and after the metal was exploded j but to avoid prolixity I have not 

 mentioned it iu the relation of the following experiments. 



4 EXPERIMENT 



