CONCLUSIONS 



13 



proportion of their combining weights^ or in simple multiples of 

 these weights. 



It has been found possible to derive the probable composi- 

 tion of a compound of two elements, by the proportion in which 

 each unites with a third. In other words, tzvo elements usually 

 unite with a third in the proportion in which they unite with 

 each other. In the case referred to, a fourth element was 

 introduced, thus : — 



Lead unites with oxygen in the proportion of 206 : 16 

 Oxygen „ hydrogen „ „ 16 : 2 



Hydrogen „ chlorine „ „ 2:71 



Therefore, 



Chlorine „ lead „ „ 71:206 



Pb — . o 



I I 



CI2 ^ — H2 



Fig. 45. 



To explain these facts of chemical combination, it is con- 

 ceived that when elements combine, it is their ultimate particles 

 or atoms that unite with each other, and that the relative weights 

 of these atoms are the combini?ig weights of the ele?7ients. Thus, 

 if the weights of atoms of oxygen and nitrogen be 16 and 14 

 times respectively the weight of an atom of hydrogen, oxygen 

 and nitrogen will combine in the proportion of these weights, 

 or in simple multiples of them. 



The laws of chemical combination have been found to hold 

 good for compounds as well as elements. Thus, hydrochloric 

 acid combines with ammonia in definite proportions. There 

 is physical evidence that of both elements and compounds 

 there are ultimate particles or molecules indivisible, without 

 altering their nature. A molecule of hydrochloric acid must 

 8 



