Answer:
You would likely combine Salicylic Acid and an acetylating reagent; (Acetic anhydride is much nicer to work with than acetyl chloride, et al); but regardless of which you use, you would need to purify the product, and recrystallize the product in very cold ethanol or another suitable reagent. After that, use a melting point apparatus first; the accepted value of Pure Aspirin, acetylsalicylic acid, is expected at 138°C-140°C. Any starting material contamination will cause the temperature to be lowered. A melting point is quick, cheap, and can be done at the lab desk. If you have a Pure Standard, you can use Gas Chromatography, but that can be time consuming compared to taking the M.P.; Proton NMR, even Carbon 13 NMR, but a good M.P. apparatus should still be done first; if the M.P. is depressed, you would need to recrystallize to see a “nice” NMR spectra. Infra Red Spectroscopy has its place, but it does have limitations. It IS quick, but you would need to know how to evaluate IR, or NMR; M.P. is convenient and also a very old, reliable test. Naturally, a 1H NMR would be nice to have as well, but for a laboratory Class exercise, likely not that essential.