The Clear Jade Alchemy Manual is an Alchemy Manual that was owned by Chen Fan so that one can be proficient on Pill Refining.
Chen Fan gave it to Wu Qingyan before he left the North Wild, but took it back 300 years later on the request of Wu Qingyan due to her family problems. Her memories of it's contents was possibly removed as well, so that no one can use it to rise up their forces by trying to Soul-Searching her, like Mount Emperor.