An acid substance contains acid.
These shrubs must have an acid, lime-free soil.
这些灌木在不含石灰的酸性土壤中才能生长。
acids
An acid is a chemical substance, usually a liquid, which contains hydrogen and can react with other substances to form salts. Some acids burn or dissolve other substances that they come into contact with.
citric acid.
柠檬酸。