226 Domestic Science 



volume of carbon dioxide is produced, some of the 

 oxygen combining during burning with the hydrogen 

 of the candle. Such a statement as " the oxygen in 

 the jar is replaced by carbon dioxide during the burning 

 of the candle " is consequently incorrect in that no 

 mention is made of the partial character of this replace- 

 ment. 



154. All our common fuels e.g. wood, coal, coal- 

 gas, paraffin oil consist chiefly of carbon and hydrogen 

 compounds, and, when burnt, produce water-vapour 

 and carbon dioxide. 



EXPERIMENT 88. Hold a clean dry glass bell-jar 

 (or large beaker) for a few seconds over each of the 

 following in turn : 



(a) A burning splinter of wood. 



(b) A small gas-flame. 



(c) The flame of a paraffin lamp. 



(d) The flame of a spirit lamp. 



Note in each case the appearance of the inside of 

 the jar, and after each test, close the mouth of the jar 

 with a large glass plate, invert, and shake up the con- 

 tents of the jar with a little clear lime-water. 



It was stated in Chapter xin that some of the opera- 

 tions which go on inside our bodies resemble burning. 

 We are now prepared to show that this resemblance is 

 very close. 



EXPERIMENT 89. Breathe into the open end of a 

 large dry cold test-tube. Note the appearance of the 

 inside of the tube after the breathing. Now pour a 

 little clear lime-water into the test-tube, and shake 

 vigorously, observing carefully any alteration in the 

 appearance of the liquid. 



From this experiment it will be clear that water- 

 vapour and carbon dioxide are both to be found in 



