The best advice for finding out whether a batch of metol is good is to mix up some D-23 and try it. Someone recently wrote about this subject and I will pass along what he said. Years ago when I could get metol from Kodak, under the Elon name, I saw that it could last a long time. It still worked after it started to turn a pale tan color. Kodak's chemicals were very high in quality. Metol comes from different places today and may contain contaminants which the Kodak product didn't. In any case, metol is still available and can be used to make up many different formulas. First a beginner, I would recommend D-23.