196 



SCIENTIFIC AMUSEMENTS. 



hydrogen burns in the air, uniting with oxygen to form water 

 (Expt. 207), what really -takes place at first is the combination 

 of gaseous hydrogen and gaseous oxygen to form water vapour 

 or steam, which does not condense to liquid water until it has 

 become greatly cooled down, much heat being produced by the 

 chemical action. By substituting certain other gases for oxygen 

 or for hydrogen in this experiment, it is possible to produce com- 

 bustion or development of heat in consequence of chemical 

 action, where the products of the action are all gaseous at 

 the ordinary temperature ; thus the gas termed carbon monoxide 

 will burn with oxygen, producing a third different gas carbon 

 dioxide (Expt. 220). Just as water vapour condenses to a 

 liquid more readily than either hydrogen or oxygen, so does car- 

 bon dioxide become more readily liquefied by considerable chilling 

 than either oxygen or carbon monoxide. The same result is 

 generally brought about in other analogous cases. 



Expt. 215. Combination of Hydrogen and Chlorine Gases. 

 Collect a small wide-mouthed jar full of chlorine by displacement 

 (Expt. 180), and another similar one full of hydrogen (Expt. 104) ; 

 bring the two jars together mouth to mouth (fig. 87), and then 

 invert them so that the hydrogen jar is lowest and the chlorine 

 jar uppermost ; in a minute or so the heavier chlo- 

 rine and lighter hydrogen will have intermixed 

 sufficiently to form a mixture of gases capable of 

 exploding with some report on cautiously separating 

 the two jars, and applying a lighted taper to their 

 mouths. The explosive action in this case arises from 

 the same cause as that operating in Expt. 208, where 

 a mixture of oxygen and hydrogen behaves similarly ; 

 a chemical action of combination takes place, hydrogen 

 and chlorine combining to form hydrochloric acid, just 

 as hydrogen and oxygen combine to form steam ; and 

 so much heat is developed during this action that a 

 considerable expansion of the gases is suddenly 

 brought about at the moment of combination. With 

 pure hydrogen and chlorine already mixed in proper 

 proportions, exposure to light will often bring about 

 combination with explosion, without any flame being 

 requisite. 



Expt. 216. Chlorine burning in an Atmosphere 

 of Hydrogen. Another way of showing the com- 

 bination of chlorine and hydrogen is illustrated by 

 fig. 88 ; a small chlorine generator is set in action, 

 the delivery pipe pointing upwards ; a jar of hydrogen is collected, 



Fig. 88. 



Chlorine 

 burning in 

 Hydrogen. 



