英语时差：阿司匹林

In the 1890’s a young scientist, named Felix Hoffman, was looking for a cure for his father’s terrible arthritis. Hoffman noticed that acetylsalicylic acid produced the benefits of the earlier drug without the side effects. In 1899, the new compound was first sold under the name of “aspirin.” Salicylic acid and acetic acid can both irritate the stomach, but when they are joined by a chemical reaction, the result is safe for most people. Unfortunately, air, heat, and moisture, can reverse that reaction turning your aspirin back into salicylic acid and acetic acid, both of which are harmful to the stomach lining. Since acetic acid is a concentrated form of vinegar, you can smell a bottle of aspirin to tell if it’s getting old. If aspirin smells strongly of vinegar, throw it away; it’s no longer aspirin.