狐丘，亦称狐刚子，道家炼丹高手。其生平不详，为晋代人，与葛洪同时期。据今人考证，其著述《五金诀》中，被誉为“最大之外丹黄白师”。此外，狐刚子的另一名有胡罡子、狐罡子，他在东汉末年是炼丹术的杰出代表之一。据传魏伯阳是他的师傅，而三国吴时的葛玄则可能是他的弟子。
他的一些重要佚文，如《五金粉图诀》（又称《粉图经》、《粉图》、《五金诀》，或称《狐刚子万金诀》）、《出金矿图录》、《河车经》、《玄珠经》，以及其他一些著作，都反映了当时中国古代化学和炼丹术的高度成就。他对黄白术方面有一定的贡献，但遗憾的是，由于文献记载不足，我们无法完整了解他的全部成就。
然而，从那些幸存下来的文献中，我们可以看出狐刚子的卓越地位。他撰写了关于服食金丹长生不死说的文章，并且提出了许多实用的方法和理论，比如“吹灰法”（即锡灰坯炉法），这是冶炼贵金属的原始形式；而“炼石胆取精华法”，则是世界上最早提取硫酸的记录，这比阿拉伯人的相同技术要早500多年。
此外，他还发明了一种名为“金银粉”的新工艺，即将黄金变成液态汞，然后与盐末混合，再蒸去水银留下极细的黄色微粒。此法至今仍被后世所用。在水银制炼史上，他提出改焙烧为密闭抽汞法，对提高回收率起到了关键作用。此外，他还对不同用途下的水银进行分类，并根据这些分类制定不同的提炼方法。
总结来说，fox just so, or fox juan zi, is a renowned alchemist of the Eastern Han period. His exact birth and death dates are unknown, but it is believed that he lived during the same time as Ge Hong. According to modern scholars, Fox Juan Zi's writings reflect a high level of sophistication in ancient Chinese chemistry and alchemy.
His contributions include the development of new methods for extracting gold and silver from ores, as well as his work on the properties of mercury. He is also credited with discovering new ways to purify metals and creating alloys. His most famous work is "The Five Metal Powder Diagram," which describes how to extract gold from ore using a combination of heat and chemicals.
Fox Juan Zi's legacy has had a lasting impact on Chinese alchemy and metallurgy. His techniques were used by later generations of chemists and metalworkers, who built upon his discoveries to develop even more sophisticated methods for extracting precious metals from ore.
In addition to his scientific contributions, Fox Juan Zi was also known for his philosophical writings on the nature of reality and the human condition. He believed that humans could achieve immortality through spiritual practices such as meditation and breath control.
Overall, Fox Juan Zi was an important figure in Chinese history who made significant contributions to our understanding of chemistry, metallurgy, and philosophy.
