A Bit of Chemistry to Ensure Safety


Lemons are great in ice tea but not so great when they accidentally come in contact with your skin or eyes.  Lemon juice has a ph level of 2.4.  This is why it can burn when you come in contact with it.  pH is a numeric scale used to specify the acidity or alkalinity of a solution. 

Last week, I explained some of the hazards of portland cement and the caustic nature of this white powder.  When mixed with moisture, portland cement becomes highly caustic (pH > 12).
It is important to know the pH of substances because they may be corrosive or react with incompatible materials. For example acids and bases should not be stored or used near each other as their accidental combination could generate a huge amount of heat and energy, possibly resulting in an explosion.  pH is also important to know in case you spill the material on your skin or in eyes. 
The pH values of some common substances are given in the table below.

Substance

Typical pH

Substance

Typical pH

Substance

Typical pH

Stomach acid (gastric juices)

1.4

 

 

Pure water

 

 

7.0

Baking soda

8.4

Lemon juice

2.4

Household ammonia

11.5

Vinegar

3.0

Household bleach

12.5

Tomatoes

4.2

Portland Cement

12 – 13

The pH scale is logarithmic. That means each change of one in pH value is 10 times more acidic. Therefore, a substance with a pH of 2 is 1000 times more acidic than one with a pH of 5!