North Fork Watershed Association
Friday, January 22, 2021



In base 10, pH is the negative log of the concentration of hydrogen ions (H+) found in an aqueous solution. The higher the concentration of H+ the more acidic the solution and the lower the pH.

This may be confusing for some since, for example, a pH of 2 is more acidic than a pH of 12, but since it is a negative log you could think of it as negative numbers where negative 12 is smaller than a negative 2.

The pH scale goes from 1-14 and here are some general examples;

 1-2 gastric juice                     8-9 baking soda                

 2-3 lemon juice                     9-10 borax    

 3-4 vinegar                                               

 4-5 tomatoes                        10-11 lime water   

 5-6 pure rainwater (5.6)          11-12 ammonia  

 6-7 milk                               12-13 bleach 

 7-8 seawater and tears                 13-14 sodium hydroxide


For more information about pH try;

ACIDS and BASES:  The differences between acids and bases can actually be a quite complex topic, but here are some basics (no pun intended).

Acids are substances that can easily (the more acid the more easily) lose a H+ from its molecular structure thereby increasing the H+ concentration in an aqueous solution, like water. The remaining part of the molecule will often find another ion to bind to, precipitate out (become solid) and thus immobile.

When rain is acidic enough it can leach out certain heavy metals from the soil by making them mobile (no longer bound) and increasing the possibility that they can locate into a water supply. This leaching can also occur with essential nutrients, such as Calcium, that are neccessary for plant growth. Without these nutrients being available in the soil, in most severe cases, forest decline could occur. Generally, smaller trees and sensitive species would show the first symptoms. Older trees could go for a time under adverse conditions because of their ability to withdraw certain nutrients from other parts of their own structure without noticeable damage. 

Bases are substances that will accept H+. The more basic the substance, the greater the ability to bind H+.

Many bases have a hydroxide (OH-) group attached, which is why this strong base so readily accepts the H+. The hydogen ion binds to the hydroxide forming a water molecule and usually drawing the pH of the remaining solution closer to neutral as it reaches equilibrium.

As with strong acids, strong bases more easily react with other substances as the molecule is relatively unstable and dissociates more readily.