Definition
A chemical condition having a pH greater than 7. Alkaline substances are the chemical opposite of acids and will neutralize them. In aviation, alkaline materials are commonly encountered in certain battery electrolytes (such as nickel-cadmium batteries) and in some cleaning agents.
Plain English
The opposite of acidic. A substance with a pH above 7, like baking soda or the electrolyte inside a Ni-Cad battery.
Context Anchor
Seen in aircraft battery maintenance, corrosion control, and cleaning-product instructions.
Derivation
From the Arabic 'al-qali,' meaning 'the ashes' — referring to the ashes of certain plants from which early chemists extracted alkaline salts. The term carried into English to describe substances with that same chemical character.
Why Pilots Care
Alkaline and acid battery electrolytes cannot be mixed, stored together, or cleaned up with the same materials. Spilling one on the wrong battery type, or using the wrong neutralizer, causes serious damage. Knowing which type of battery is installed determines how it is serviced safely.
Intuition Check
Alkaline does not mean mild, safe, or simply battery-related. It means basic rather than acidic, and some alkaline substances can burn skin or damage materials.
Example Sentence 1
The nickel-cadmium battery uses an alkaline electrolyte, so any spill must be neutralized with a mild acid rather than baking soda.
Example Sentence 2
Alkaline cleaners must be rinsed thoroughly to avoid damaging aircraft aluminum surfaces.