MATTER 27 



long series of homologous compounds, and it is a most 

 remarkable fact, that in the compounds of one series 

 the elements exist in the same relative amounts. For 

 example, the following six formulas of this series 

 show that there are twice as many atoms of hydrogen 

 as of oxygen in each compound. C2 H*, C3 H 6 , C4 Hs, Cs 

 H10, Ce H12, C7 Hu. The analysis of any one of these 

 compounds shows that there is by weight six parts of 

 carbon and one of hydrogen, and from this it might 

 seem that, one formula would serve for each of the six 

 compounds, and yet the chemist is certain from the 

 specific gravities of the vapors of these compounds 

 that the above are the correct formulas. 



But more remarkable than the above is the fact 

 that sometimes different compounds must be repre- 

 sented by the same formulas. For example, several 

 different compounds have the formula C5 H10, and 

 others the formula C2 H* CI2. In these cases of 

 isomerism the molecular weights of the substances are 

 the same, and we can only account for [the difference 

 in the properties of the compounds by assuming that 

 the atoms are combined in them in different ways. 

 We can easily imagine that the fifteen atoms in the 

 formula Cs H10 might be differently grouped with 

 each other so as to form compounds of different 

 qualities, on the same principle that fifteen blocks of 

 two different kinds might be arranged in different 

 ways. 



I may here state that there is no distinction be- 

 tween Organic and Inorganic Chemistry. It was 

 formerly thought that organic compounds could not 

 be produced artificially from the elements or from 

 inorganic substances, but that they could be built up 

 by living organisms only, or produced from matter 

 organized by plants and animals. Chemists have,, 



