Learn the pH of Common Chemicals

pH is a measure of how acidic or basic a chemical is when it's in aqueous (water) solution. A neutral pH value (neither an acid nor a base) is 7. Substances with a pH greater than 7 up to 14 are considered bases. Chemicals with a pH lower than 7 down to 0 are considered acids. The closer the pH is to 0 or 14, the greater its acidity or basicity, respectively. Here's a list of the approximate pH of some common chemicals.

pH of Common Acids

Fruits and vegetables tend to be acidic. Citrus fruit, in particular, is acidic to the point where it can erode tooth enamel. Milk is often considered to be neutral, since it's only slightly acidic. Milk becomes more acidic over time. The pH of urine and saliva is slightly acidic, around a pH of 6. Human skin, hair, and nails tends to have a pH around 5.

0 - Hydrochloric Acid (HCl)
1.0 - Battery Acid (H₂SO₄ sulfuric acid) and stomach acid
2.0 - Lemon Juice
2.2 - Vinegar
3.0 - Apples, Soda
3.0 to 3.5 - Sauerkraut
3.5 to 3.9 - Pickles
4.0 - Wine and Beer
4.5 - Tomatoes
4.5 to 5.2 - Bananas
around 5.0 - Acid Rain
5.0 - Black Coffee
5.3 to 5.8 - Bread
5.4 to 6.2 - Red Meat
5.9 - Cheddar Cheese
6.1 to 6.4 - Butter
6.6 - Milk
6.6 to 6.8 - Fish

Neutral pH Chemicals

Distilled water tends to be slightly acidic because of dissolved carbon dioxide and other gases. Pure water is nearly neutral, but rain water tends to be slightly acidic. Natural water rich in minerals tends to be alkaline or basic.

7.0 - Pure Water

pH of Common Bases

Many common cleaners are basic. Usually, these chemicals have very high pH. Blood is close to neutral, but is slightly basic.

7.0 to 10 - Shampoo
7.4 - Human Blood
7.4 - Human Tears
7.8 - Egg
around 8 - Seawater
8.3 - Baking Soda (Sodium Bicarbonate)
around 9 - Toothpaste
10.5 - Milk of Magnesia
11.0 - Ammonia
11.5 to 14 - Hair Straightening Chemicals
12.4 - Lime (Calcium Hydroxide)
13.0 - Lye
14.0 - Sodium Hydroxide (NaOH)

Other pH Values

Soil pH ranges from 3 to 10. Most plants prefer a pH between 5.5 and 7.5. Stomach acid contains hydrochloric acid and other substances and has a pH value of 1.2. While pure water free of undissolved gases is neutral, not much else is. However, buffer solutions may be prepared to maintain a pH near 7. Dissolving table salt (sodium chloride) in water does not change its pH.

How to Measure pH

There are multiple ways to test the pH of substances.

The simplest method is to use pH paper test strips. You can make these yourself using coffee filters and cabbage juice, use Litmus paper, or other test strips. The color of the test strips corresponds to a pH range. Because the color change depends on the type of indicator dye used to coat the paper, the result needs to be compared against a chart of standard.

Another method is to draw a small sample of a substance and apply drops of pH indicator and observe the test change. Many home chemicals are natural pH indicators.

pH test kits are available to test liquids. Usually these are designed for a particular application, like aquaria or swimming pools. pH test kits are fairly accurate, but may be affected by other chemicals in a sample.

The most accurate method of measuring pH is using a pH meter. pH meters are more expensive than test papers or kits and require calibration, so they are generally used in schools and labs.

Note About Safety

Chemicals that have very low or very high pH are often corrosive and can produce chemical burns. It's fine to dilute these chemicals in pure water to test their pH. The value won't be changed, but the risk will be reduced.

Sources

• Slessarev, E. W.; Lin, Y.; Bingham, N. L.; Johnson, J. E.; Dai, Y.; Schimel, J. P.; Chadwick, O. A. (November 2016). "Water balance creates a threshold in soil pH at the global scale". Nature. 540 (7634): 567–569. doi:10.1038/nature20139