30 Introduction 



If a substance when dissolved produces hydrogen ions, it is known 

 as an acid. Hydrochloric acid dissociates in this way : 



HCl > H+ + Cl- 



If instead of producing hydrogen ions in water solution, a sub- 

 stance produces hydroxyl (OH) ions, it is known as a base. In this 

 event, the hydrogen and oxygen are bound together in such a manner 

 that they react as a single unit. This unit is known as a radical; in 

 the case of bases, it is the hydroxyl radical. This radical carries an 

 electrical charge similar to that of any other ion. Sodium hydroxide 

 ionizes in this way : 



NaOH > Na+ + OH- 



If an acid and a base are placed together in water solution, a re- 

 action illustrated by the following formula occurs : 



NaOH -f- HCl > NaCl -f H.O 



Thus when an acid and base are placed together, a salt and water result. 

 This salt when dissolved never yields hydrogen or hydroxyl ions. 



Some acids and bases ionize to a greater degree than do others. 

 Acids such as hydrochloric and bases such as sodium hydroxide ionize 

 almost completely. They are classed as strong acids and bases. Acids 

 that produce but few hydrogen ions are considered weak acids ; likewise 

 bases that produce few hydroxyl ions are called weak bases. 



In pure water, the hydrogen and hydroxyl ions balance completely 

 and the reaction of the water is indicated as neutral. An acid or basic 

 reaction, of course, indicates the presence of either the hydrogen or 

 hydroxyl ions. The degree of acidity of a solution is indicated by the 

 usage of the term pH. Distilled water has a pH of 7, which is neu- 

 trality. Values below that indicate increasing numbers of hydrogen 

 ions; values above indicate the presence of hydroxyl ions. A pH of 

 5 is considered to be a strongly acid reaction. 



ORGANIC CHEMISTRY 



Chemistry is considered to have two major branches : the one 

 dealing with the chemistry of the carbon compounds is organic; that 

 dealing with the chemistry of all other materials is inorganic. 



Organic compounds far outnumber the inorganic. The reason for 

 this large number is traceable to the fact that the individual carbon 



