xv THE MOLECULAR THEORY 333 



remained over exactly 50 parts of nitrogen, the weight of 

 which, deducted from that of the nitrous gas (determined 

 with great care by M. Be'rard at Arcueil), yields as result 

 that this gas is composed of equal parts by volume of 

 nitrogen and oxygen. 



We may then admit the following numbers for the pro- 

 portions by volume of the compounds of nitrogen with 

 oxygen. 



Nitrogen. Oxygen. 



Nitrous oxide 100 50 



Nitrous gas .... 100 100 



[Nitrogen peroxide] . . . 100 200" 



(A.C.R. IV. 13-14.) 



From the observations recorded above Gay-Lussac 

 concluded that "gases always combine in the simplest 

 proportions when they acton one another" (A.C.R. IV. 15). 



Extension of the law of volumes to the products 

 formed by the interaction of gases. Further experiments 

 convinced Gay-Lussac that : 



" Not only, however, do gases combine in very simple 

 proportions, as we have just seen, but the apparent con- 

 traction of volume which they experience on combination 

 has also a simple relation to the volume of the gases, or at 

 least to that of one of them." 



"I have said, following M. Berthollet, that 100 parts of 

 carbonic oxide gas, prepared by distilling oxide of zinc and 

 strongly calcined charcoal, produce 100 parts of carbonic 

 gas on combining with 50 of oxygen. It follows from this 

 that the apparent contraction of the two gases is precisely 

 equal to the volume of oxygen gas added." 



" We know, besides, that a given volume of oxygen 

 produces an equal volume of carbonic acid ; consequently 

 oxygen gas doubles its volume on forming carbonic oxide 

 gas with carbon, and so does carbonic gas on being passed 

 over red-hot charcoal." 



" Oxygen gas, in combining with sulphur to form 

 sulphurous gas, only experiences a diminution of a fiftieth of 

 its volume, and this would probably be nil if the data I have 

 employed were more exact." 



