I found some MDPV in water a while back and found it to be about 50% weaker than when first dissolved about 4 weeks before. I was wondering if any other my noticed the same thing? I had not used it in many weeks (or any other stimulants) and does not feel tolerance was a factor. The water was kept cool but was in a transparent container. No color changes or other signs of degredation were noted, but it was a 10mg/ml solution, which is pretty dilute.