A soil with a pH of 6.0 has ten times as many hydrogen ions (H+) present as a soil pH of 7.0 and a soil with a pH of 5.0 is 10 times more acid than pH 6.0. In other words the pH scale is designed so that a change of one point actually means a ten fold change in soil reaction That is what is meant by a logarithmic scale. That is why it takes much more lime to change soil from pH 5.0 to 6.0 than to change it from 6.0 to 7.0.

Following are some examples of materials that fall along the scale of pH.

14.0     Sodium Hydroxide

13.0     Lye

12.4     Lime (Calcium hydroxide)

11.0    Ammonia

10.5     Milk of Magnesia

8.3       Baking Soda

7.4       Human Blood

7.0       Pure Water Neutral

6.6       Milk Acid

4.5       Tomatoes

4.0       Wine & Beer

3.0       Apples

2.2       Vinegar

2.0       Lemon Juice

1.0       Battery Acid

0          Hydrochloric Acid