OF THE ATOMIC THEORY. 39 



and 1 atom lead ought to be 9*321 ; but it 

 amounts only to 8'817, showing that an expan- 

 sion has attended the union of these metals, in- 

 stead of a contraction. 



3. Berzelius, in his different papers upon the 

 atomic theory, and especially in his Essay on a 

 the Theory of Chemical Proportions, has made 

 us aquainted with the rules that guided him in 

 the conclusions which he has drawn respecting 

 the atomic weights of the different bodies, and 

 the number of atoms of which the compound 

 bodies are composed. The most important of 

 these laws are the following : 



(1.) One atom of A may combine with 1, 2, 3, 

 4, &c. atoms of B. We do not know the limit ; 

 but it rarely passes 5 atoms. 



(2.) Two atoms of A may combine with 3 

 atoms of B. But this is a much rarer case than 

 the preceding. 



(3.) When an acid and a base unite, the 

 oxygen in the acid is a multiple of that in the 

 base by 1, 2, 3, &c. The only exceptions to 

 this law, exist in the combinations of phosphoric, 

 arsenic, and nitric acids with bases. 



(4.) Oxides containing only 1 atom of oxygen, 

 united to 1 atom of base, have very weak affi- 

 nities for acids. 



(5.) Oxides with 2 atoms of oxygen have very 

 strong affinities for acids. 



(6.) Oxides with 3 atoms of oxygen have weak 

 c 4, 



