What is acid? Md. Saifur Rahman The substances with sour taste that turn blue litmus to red and donate hydrogen ion in aqueous solution are called acids. You may likeDo I need car insurance?What is car insurance?How could I get cheaper car insurance?What is auto insurance?Why Adulterant food is the barrier to sound health?What are the producers?What are food preservatives?What is food chain?What is tertiary consumer?