io6 COMPOUND RADICLES. PARTI. 



other may also be made in organic bodies, but chlorine, 

 bromine, and iodine form an exception to M. Dumas's 

 law, because the arithmetical relation is wanting. 



There are certain groups of substances, especially 

 among the metals, whose atomic weights are in regular 

 arithmetical series, as those of titanium, tin, and tan- 

 talum, which are 25, 59, and 92, the common difference 

 being 34. 



Certain groups of combined atoms called compound 

 radicles are much more important than the preceding. 

 They unite chemically with one another, and with other 

 substances in definite proportions, precisely as if they 

 were ultimate atoms. They are even capable of being 

 substituted one for the other, forming groups of infinitely 

 varied properties, and thus chemical equivalency extends 

 to them. 



Cyanogen, amidogen, and the peroxide of hydrogen 

 are compound radicles which combine with other sub- 

 stances and with simple atoms as if they themselves 

 were simple elements ; though the first is a chemical 

 compound of two atoms of carbon and one of nitrogen, 

 the second a chemical compound of one atom of nitrogen 

 and two of hydrogen, and the peroxide contains as 

 before mentioned two atoms of oxygen and one of 

 hydrogen. All three are capable of replacing hydrogen, 

 chlorine, and metals by equivalent substitutions. For 

 example, the chlorate of potash consists of one atom of 

 potash, an atom of chlorine, and five atoms of oxygen ; 

 if then an atom of cyanogen whose weight is 26, be put 

 for the atom of chlorine, the result would be the cyanate 

 of potash. 



Cyanogen, formed by passing nitrogen over red-hot 

 carbon, consists of two equivalents of carbon and one of 

 nitrogen. It is a frequent constituent of organic and 

 inorganic compounds, and travels in the voltaic circuit 

 as if it were a simple substance. 



