THE MODERN THEORY OF CHEMICAL TYPES. 



159 



sity, atomic volumo, &c., became known ; out of which accessions to our knowl- 

 edge was developed the modern type theory. 



The compound ammonias are bases bearing a very great analogy to ammo- 

 nia, their salts being strictly analogous. By the former radical theory it would 

 be" impossible to assign to them satisfoctory formulae ; but by the assumption 

 that they are constituted after the pattern or type of ammonia, their formula} 

 become very simple. They are ammonias, in which one or more atoms of hy- 

 drogen are replaced by one or more radicals, thus : 



Type H > N = Ammonia. 

 H) 



Efhylamine. Diethylamine. 



(C.Hs) ) (C4H5) ) 



H S N. (C4H5) } N. 



H N H N 



Triethylamine. 



(CJI5) ) 



The laws alluded to above which enable a more correct conception of the 

 chemical constitution of bodies are as follows : 



1. T//e hat) of even atoms. — The remarkable fact has been discovered that 

 (the cqivalents of and H being 8 and 1) by far the greatest number of 

 organic compounds contain an even number of carbon atoms ; further, that the 

 nmi of the atoms of hydrogen, chlorine, iodine, bromine, nitrous oxide, (N O4.) 

 nitrogen, and metal is an even number ; which is also true for the sum of their 

 oxygen and sulphur-atoms. For example, in Benzoic acid Ch Hg O4 the number 

 of cai'bon atoms is an even number, and so is that of the hydrogen and of the 

 oxygen atoms. 



2. The law of atomic volume. — The greater portion of organic compounds ex- 

 perience in the vaporous condition a condensation during the combination of 

 their elements to four volumes — in other words, in the state of vapor their 

 atom occupies four times the volume of an oxygen atom. This, law, it will be 

 remembered, is seen by comparing the quotients arising from a division of the 

 equivalents of compounds by the speciiic gravity of their vapors, and gives the 

 result that the atomic volume of the atoms of the elements and their compounds 

 bear a simple relation to each other, as may be seen from the following table, 

 which is quoted from its bearing upon the type theory : 



Names of bodies. 



Suiphur 



Oxygen 



Phosphorus 



Hytlrogen 



Nitrogen 



Chlorine 



Bromine 



Iodine 



Water 



Sulphuretted hydrogen 



Carbonic acid 



Protoxide of nitrogen. 

 Deutoxide of nitrogen. 



Hj-drochloric acid 



Ammonia 



Chloride of ethyle 



Acetic acid 



Valerianate of ethyle. 



Symbol. 



S 



o 



p 



n 



N 



CI 



Br 



I 



HO .... 

 HS 



CO2 



NO 



NO, 



HCl 



NH3 



C4 Hi CI. 



C4 H4 O4. 



Ch Hi4 O4 



Division of the 

 equiv. by the 

 sp.gr. of vapor. 



Relative atomic 

 volume. 



2.41 



7. 22 

 7.22 

 14.44 

 14. 44 

 14.44 

 14.44 

 14. 44 

 14.44 

 14.44 

 14.44 

 14.44 

 28.88 

 28. 88 

 28.88 

 28.88 

 23.83 

 23.88 



Atomic volume. 

 Oxygen = 1. 



