Recognizing the importance of harm reduction and open science, the Shulgins authorized the online library to host the entire second half of PiHKAL (the chemical manual) for free.
You can borrow or download a digital copy from the Internet Archive.
While the "free PDF" floating around the internet is primarily utilized by amateur chemists and curious psychonauts, it is also heavily referenced by researchers, pharmacologists, and emergency medical professionals. Understanding the chemical structure and effects of these substances (which are collectively known as Shulgin psychedelics) is critical for medical professionals treating individuals who have ingested novel psychoactive substances (NPS). Understanding the Legal and Ethical Nuances