4. OPERATIONS AND INSTRUMENTS 



The utmost degree of mechanical division which 

 we can effect in bodies, by pounding, grinding, and 

 similar processes, can only reduce them to frag- 

 ments so small that they can no longer be per- 

 ceived by the sight ; but we cannot thus arrive at 

 those ultimate atoms, molecules, or particles, of 

 which the various s])ecies of matter are sup})osed to 

 consist, and which arc, perhaps, incapable of 

 subdivision. 



Besides the attraction of gravitation possessed 

 in common by all matter, these elementary sub- 

 stances possess peculiar attractions for each other, 

 whi-cli are called chemical attractmis. By these 

 attractions, or affinities, as they are called, they 

 combine together, and form com])oimd bodies. 



OPERATIONS AND INSTRUMENTS USED IN 

 CHEMISTRY. 



The great principle of all chemical operations 

 which enable us to decompose certain bodies, and 

 to compound others, is, that every substance has a 

 pecidiar affinity or attraction for other substances, 

 but that it has different degrees of attraction for 

 different substances. This is called elective affinity 

 or attraction. 



If some oil and some alkali be put together, they 

 will unite and form soap. But if to this a little 

 dilute sulphuric acid be added, the oil and alkali 

 will be separated from each other again ; the alkali 

 having a stronger attraction for the acid than it has 

 for the oil, will leave the latter and join the acid. 



Dissolve some magnesia in nitric acid, and the 

 solution will be transparent. Also dissolve some 

 lime in water by letting it remain for some 

 hours: the solution of lime in water will also 



