LECTURE XXVII. 



CHEMISTRY. 



MIXTURE, AND ITS EFFECTS. 



THE following principles may be laid down 

 with respect to mixture. 



1. We find that some bodies cannot be made 

 to unite with others, as oil and water, and water 

 and quicksilver : however shaken together, they 

 will still separate again. 



2. We find others unite in the most intimate 

 manner, and form a compound in appearance 

 perfectly homogeneous. Of these some unite 

 slowly and gently, as salt and water. 



3. There are other cases, where the union is 

 attended with perturbation and commotion ; the 

 production of heat, smoke, and sometimes flame. 

 If I pour into a flask a quantity of water quite 

 cold, and I add an equal quantity of sulphuric 

 acid, which has a great tendency to mix with 

 water, and is likewise cold, the liquid becomes 

 hot, so as actually to boil, emit steam, &c. 



Again If I drop a little carbonate of ammo- 

 nia, which is a volatile salt (in a fluid state), 

 into sulphuric acid (this experiment requires 

 cantion), the agitation is greater than if a red-hot 



