CHAPTER XIII 

 PHYSICO-CHEMICAL PROCESSES 



152. Nature of Physico-Chemical Processes. Certain 

 processes like: 



1. Solution 6. Filtration 



2. Ebullition 7. Crystallization 



3. Evaporation 8. Sublimation 



4. Precipitation 9. Distillation 



5. Clarification 



are physical in character, though used extensively in combina- 

 tion with certain chemical processes. They must be con- 

 sidered, therefore, in discussing the principles of chemistry. 



153. Solution. When a solid substance is placed in a 

 liquid and dissolves without a change in its chemical struc- 

 ture, the resulting liquid is said to be a solution of the dis- 

 solved substance. The liquid used is called the solvent of 

 the substance. As an illustration: Sugar dissolved in water 

 forms a solution of sugar. When the water will dissolve no 

 more sugar, it is said to be a saturated solution at that 

 temperature. A liquid saturated with one substance may 

 still be a solvent for another substance. 



154. Ebullition. Ebullition or boiling is the violent agi- 

 tation produced in a liquid when it is heated from a liquid 

 to a gaseous condition. The heat acts first oh that portion 



143 



