Acids are compounds that increase the amount of hydrogen ions (+ H) in water. Therefore, the amount of hydrogen ions (+ H) in the medium is a measure of the acidity of that medium. That is, the more hydrogen ions in the environment, the more acidic the environment.

General properties of acids:

• They have a sour taste.
• They contain hydrogen (H) which can be replaced by a metal.
• With some metals, such as iron and zinc, they give hydrogen gas.
• They react with alkalis (bases) and form salts. (They react strongly with calcium carbonate, for example in the form of marble, so that they foam and release carbon dioxide.)
• They have a low pH.
• Neutralize the bases.
• They change the color of some materials (identifiers) (turn red litmus paper).
• Their aqueous solution releases proton ions.

Types of acids

1- Mineral acids that are formed from the combination of some elements with hydrogen. These acids are chemical and industrial and they can not be touched or smelled and special tools and equipment are used in the laboratory. Some of the strong mineral acids are:

• Ink salt (hydrochloric acid)
• Sulfur ink (sulfuric acid)
• Dandruff ink (nitric acid)
• Hydrobermic acid
• hydrochloric acid
• Hydroic acid

And some of the weak mineral acids are:

• Hydrobermic acid
• Hydroic acid
• Perchloric acid
• Boric acid
• Carbonic acid
• Chloric acid
• Hydrofluoric acid
• Phosphoric acid
• Hydrosulfuric acid
• Nitric acid
• Phosphoric acid

2. Some acids are made by living organisms called organic acids. These acids are edible and do not cause much harm when in contact with the hand. In general, all organic acids are weakly acidic. like the:

• Acetic acid (in vinegar)
• Citric acid (in pineapple and citrus)
• Formic acid (in grapes)
• Lactic acid (in red fruits, milk and sour yogurt)