CHAP. x. THE GREAT PROBLEMS OF CHEMISTRY. 89 



tional weight the atomic weight. Thus H means a 

 unit weight of hydrogen; C means 12 times that weight 

 of carbon; Fe (ferrum) means 56 times that weight of 

 iron. Hence the symbol for any compound substance 

 tells us in the most compact form possible, not only the 

 elements of which it is composed, but the exact propor- 

 tions in which these elements are combined. Thus 

 C 2 II 6 O is the chemical symbol for pure alcohol, show- 

 ing that it is a compound of two atoms of carbon, six of 

 hydrogen, and one of oxygen. Looking now at a table 

 of atomic weights, we find that this gives us 24 carbon, 

 6 hydrogen, and 16 oxygen in each 46 parts of alcohol. 

 By means of these symbols and the accurate determina- 

 tion of atomic weights, all the complex combinations 

 and decompositions that occur during the investigations 

 of the chemist can be represented in a kind of chemical 

 algebra, and the peculiar formulae thus obtained often 

 suggest further experiments leading to new discoveries. 



Almost at the same time that Dalton was working at 

 his atomic theory, Davy (afterward Sir Humphrey Davy) 

 made the remarkable discovery of two new elements by 

 decomposing soda and potash by means of an electric 

 current, resulting in the production of the metals, 

 sodium and potassium. This placed in the hands of 

 chemists a powerful agent which led to the discovery of 

 other elements, though in this respect it has been sur- 

 passed by spectrum analysis, which is equally effective in 

 the domains of chemistry and astronomy. 



Among the more interesting discoveries of modern 

 chemistry are the methods of liquefying the various 

 gases, and even solidifying many of them; while by 

 means of the intense heat of the electric furnace all the 



