Aspirin and monitor: what they have in common

1. Step 1. Aspirin — uses — Chemical reaction. It is synthesized by acetylating salicylic acid.
2. Step 2. Chemical reaction — is used in — Litmus. Colour from acidity.
3. Step 3. Litmus — evolved into — pH meter. A replacement for indicators.
4. Step 4. pH meter — has part — Liquid-crystal display. An indicator.
5. Step 5. Liquid-crystal display — is part of — Monitor. Then LCDs.

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