1820.] the Atomic Theory. 207 



the quantity of oxygen in the other. This law has been laid 

 down by Berzelius, and indicates a most important regularity in 

 the relative weights of the atoms of bodies. 



31 . Water is capable of combining both with acids and bases ; 

 when it unites with an acid it acts the part of a base, and con- 

 tains the same quantity of oxygen that the base would contain. 

 Therefore, the least quantity of water that can combine with 

 sulphuric acid is 22'5 Avater to 77-5 acid ; for 8 : 9 :: 20 : 22-5. 

 That is to say, 8, the atom of oxygen is to 9, the integrant par- 

 ticle of water, as 20 oxygen is to 22'5 water; and the water 

 forming a base, in 100 sulphuric aciu, it must contain 20 oxygen. 

 This acid has, therefore, no more water tlian is barely sufficient 

 for its formation : hence it is the strongest possible. Such com- 

 pounds are called hydrates. This canon has also been laid down 

 by Berzelius. 



32. In combinations composed of more than two bodies con- 

 taining oxygen, the oxygen of that constituent which contains 

 the least of it is a common divisor of all the portions of oxygen 

 found in the other bodies. This law, likewise laid down by Ber- 

 zelius, depends on the fact that oxygen always unites by atoms, 

 whence it follows that any quantity of oxygen will always be 

 divisible by one atom of oxygen. Dr. Thomson observes that if 

 we were accurately acquainted with the constitution of the 

 earths, this law would be of great use to the mineralogist. It 

 would enable him to distinguish between chemical combinations 

 and mechanical mixtures. 



33. When two combustible bases unite, they always combine 

 in such a proportion that when oxidized, either the quantity of 

 oxygen uniting with each will be the same, or the oxygen in the 

 one will be twice, thrice, &c. that in the other. This is another 

 law laid down by Berzelius, and depends on this fact that the 

 two bodies must unite, atom to atom, or a certain number of the 

 atoms of the one must combine with one atom of the other. Dr. 

 Thomson applies this law to determine which of the metalhc 

 alloys are chemical combinations, and which are mechanical 

 mixtures. There can be no doubt that copper and zinc combine 

 chemically. Now the weights of the atoms of these metals are : 



Copper 8-000 



Zinc 4-315 



Therefore, if they imite atom to atom, brass ought to be a 

 compound of 100 copper and 53-93 zinc, 8 : 4-315 :: 100 : 53-93. 

 Actual analysis shows this to be very nearly the proportion of 

 the ingredients. 



34. Those are the canons of Berzelius, but founded on analy- 

 sis. (Thomson's J «?j«/s, ii. p. 40.) By means of them he deter- 

 mines the proportion of oxygen in bodies, and the number of 

 atoms of which they are composed. These laws give a facility 

 and elegance to our chemical investigations scarcely to be 



