ELECTIVE AFFINITY. 



37 



water, the camphor will be set free, because the al- 

 cohol combines with the water. So, also, all the 

 gum resins which are insoluble in water are libera- 

 ted in the same manner. Sulphuric acid has an 

 affinity for the following substances, in the order in 

 which they are arranged. 



.Sulphuric acid will be separated from any of these 

 bodies by adding any one above. For example, it is 

 separated from magnesia by ammonia, from am- 

 monia by lime, &c., but none can withdraw it from 

 baryta. Geological phenomena furnish numerous 

 instances of simple and compound elective affinitjs 

 which we shall hereafter find occasion to notice \ 

 in the mean time, we must pass on to other sub- 

 jects. There are numerous other points of great 

 interest connected with chemistry, which it might 

 be profitable to dwell upon did our limits permit. 

 We have only alluded, and that in a very cursory 

 manner, to such laws and principles as are abso- 

 lutely essential to an intelligible comprehension of 

 geological phenomena; and the more thoroughly 

 these principles are studied and understood, the 

 more attractive and interesting will the science of 

 geology appear. 



Baryta. 



Strontia. 



Potassa. 



Soda. 

 Lime. 

 Ammonia. 



Magnesia. 



