24 CHEMISTRY, AS APPLIED TO THE 



CHEMISTRY, AS APPLIED TO THE MANUFACTURE OF 



COAL-GAS. 



NOTWITHSTANDING the infinite variety which is presented to us in the con- 

 templation of the materials of which our globe is formed, we are enabled to 

 resolve them, by the aid of science, into a few simple substances or elements. 

 Between fifty and sixty of these elements have been enumerated ; but as many 

 are rarely met with, practically speaking, they are less numerous. 



The force which unites these bodies, and thus forms the various compounds 

 we have observed, so different in their characters and appearances, is called 

 affinity ; and Chemistry may be defined to be the science which observes and 

 classifies the phenomena produced by this force, and determines the laws by 

 which its action is regulated. To the chemist, then, a thorough knowledge 

 of these laws of affinity is all-important ; they furnish him with the means of 

 wresting from Nature her most hidden secrets, and of imitating her in her 

 mysterious operations. To the gas engineer they are not less important, for 

 they enable him to explain the interesting phsenomena which are developed in 

 the formation of coal-gas, and supply him with a sure guide in the various 

 processes of his art. 



In the following propositions, I think, will be found imbodied all that is 

 essential to the study of these laws. 



1 . A compound body, so long as it is possessed of the peculiar properties 

 which distinguish it as a species, is always formed of the same elements. By 

 no other than these can it be formed. Thus water always consists of two 

 elements, oxygen (O) and hydrogen (H) ; no other substances are capable of 

 forming it, in whatever way they can be combined. 



2. The elements of a body are always united in a determinate proportion ; 

 this proportion is fixed and invariable, whether the substance has been formed 

 ages ago by the operations of nature, or but recently in the vessels of the 

 chemist. 



