328 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



" From the temperature of melting ice to that of boiling 

 water, equal volumes of atmospheric air represented by 100 



became 137-40, 137*61, 137*44, i37'55> i37'48, i37'57 of 

 which the mean is nearly 137 -50" (loc. tit. p. 165). 



FIG. 47. GAY-LUSSAC'S APPARATUS FOR MEASURING THE EXPANSION OF 

 GASES AND VAPOURS. 



The globe B is provided with a tap worked by a lever LL. After filling it with 

 gas, the globe is fixed in the iron cage EFGH and immersed in a copper vessel AD 

 full of water. The curved tube ID leads to a trap KX filled with mercury. 



The increase of volume for four different gases was shown 

 (loc. cit. p. 167) in a table as follows : 



Expansion. Differences. 

 Atmospheric air .... 37 '50 



Hydrogen 37 -52 +cro2 



Oxygen 37 -48 -0-02 



Azote 37 '49 -0*01 



