Air 221 



Pour water into the reservoir, E, keeping the taps 

 P, P, closed. Light the burner, B, using only a small 

 flame at first. Gradually increase the gas supply until 

 the gauze is at red heat, and no more bubbles escape 

 from the end of the delivery tube. Place the jar J in 

 position on the beehive cell, and turn the stopcocks 

 P, P, so that a slow stream of air passes along the tube 

 over the heated copper. The rate at which the air 

 passes must not be so great that the bubbles rising in 

 the jar cannot be easily counted. 



When the jar is full of gas, turn off the taps, dis- 

 continue the heating, and remove the end of the 

 delivery tube from the water. 



After the tube has become cold, remove the copper 

 gauze and weigh it carefully. Test the gas collected 

 in the jar with respect to its power of supporting the 

 burning of a taper. 



From this experiment we learn that copper, when 

 strongly heated, burns, i.e. combines with the oxygen 

 of the air to form copper oxide, but does not combine 

 with the nitrogen. The combination with oxygen is 

 also attended by increase of weight. This experiment 

 may be repeated using a layer of "reduced" iron in the 

 place of the roll of copper gauze. In this case it is better 

 to weigh the tube and iron together before heating, and 

 to weigh tube together with iron oxide after it has 

 cooled. Had we carefully collected and weighed the 

 products of oxidation (combination with oxygen) of a 

 candle, phosphorus, magnesium, and iron filings we 

 should have found that in each case these products 

 weighed more than the original candle, phosphorus, 

 magnesium, or iron respectively. This increase in 

 weight is in every case the weight of the oxygen which 

 has entered into combination. 



