Aspirin and railway track: what they have in common

1. Step 1. Aspirin — is made of — Coal. The raw materials of early pharmaceutical synthesis were products of coal tar distillation.
2. Step 2. Coal — is material for — Coke. Coke is baked coal.
3. Step 3. Coke — is used in — Steel works. The steel works’ blast furnaces run on coke.
4. Step 4. Steel works — has part — Rolling mill. Rolling mills.
5. Step 5. Rolling mill — is used in — Railway track. Rails are rolled.

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