What Is the pH of Distilled Water?

Distilled water has been purified by using a distiller to turn it into vapor, so that any extra substances are eliminated, and then the vapor is turned back to water by condensing. The pH measurement defines the acidity or alkalinity of a solution, and 7 is neutral. The perfect distilled water has a completely neutral pH, but this is difficult to achieve in practice.

Significance

In the pH measurement, "p" stands for the German word potenz, meaning power, and the "H" for hydrogen. The equation measures hydrogen ion concentration, which identifies the acidity or alkalinity of a substance. The pH scale ranges from 0 to 14, with numbers lower than 7 acidic and numbers over 7 alkaline.

Features

Distillation involves boiling water in an enclosed system until it has completely turned into steam, which removes many microscopic contaminants such as bacteria, along with salt and hard minerals including calcium, iron, and magnesium. The solid materials are too heavy to be converted into vapor. Simply boiling water for a long enough time will remove bacteria and salt, but not other substances.

Identification

Distilled water ideally consists of only hydrogen and oxygen, with a completely neutral pH of 7. In reality, it almost always is slightly acidic, from 5.6 to just under 7, because the water absorbs carbon dioxide from the air. A gallon of distilled water can be made neutral by adding 1/8 tsp. of baking soda, a substance with a pH of 8.

Function

Distilled water is used for scientific research when purity and neutrality is essential. It also is used in industrial applications where mineral deposits from hard water can cause damage. People buy distilled water for use in steam irons, radiators, and vehicle batteries, because mineral deposits can ruin them. Distilled water also is good for watering plants due to its neutral pH. It is fine for drinking as well, but has a very bland taste which most people do not care for. Distilled water can be purchased in gallon containers in supermarkets and other retail stores.

Considerations

Many liquids people commonly consume are on the acidic side. Coca-Cola has a pH of 2.5, which rises as the soda goes flat and the carbon dioxide level decreases. Lemon juice registers around 2.0, and milk 6.5. The lowest numbers are poisonous, such as sulfuric acid and hydrochloric acid at near 0. On the opposite end of the scale, asparagus has a pH of 8 and watermelon a pH of 9. Highly-alkaline solutions are poisonous just as highly-acidic ones are, such as ammonia at nearly 12, and lye at 14.

Resources

• The chemical formula for distilled water
• pH values of common items