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Pungent, hot, toxic. Long-term use causes tendon contraction. The processing method involves wrapping it in yellow clay and firing it in charcoal fire for one day and one night before it can be used. It is incompatible with sheep blood and is not used in decoctions.

The *Shennong Bencao Jing* (Divine Farmer's Materia Medica) states: It treats chills and fever, scrofula (lymphatic tuberculosis), necrotic tissue, wind-bi syndrome, as well as hard masses and pathogenic factors in the abdomen.

[Invention] Li Shizhen said: Shi (a type of arsenic stone) is similar to Pi Shi (Arsenic Stone), and their properties are also similar. However, Pi Shi has a slight yellow halo, while Shi is entirely white, allowing for some distinction. Nevertheless, in ancient prescriptions, Shi and Fan Shi (Alum Stone) were often confused due to the similarity of their characters. However, Fan Shi is cold in nature and non-toxic, whereas Shi is hot in nature and toxic; this must not be overlooked. *Leigong Paozhi Lun* records that it eliminates accumulated qi in the diaphragm, cold-damp wind-bi, and itching lasting for ten years. Zhang Zhongjing stated: When used raw, it damages the heart and liver. In severe winter, when placed in water, the water does not freeze, indicating its hot and toxic nature is no less than that of Pi Shi. Nowadays, pharmacies often use it to substitute for Pi Shi, but Shi can only break down accumulations and attack bi-syndromes; it cannot resolve phlegm and dissipate nodules. Therefore, the ineffectiveness of Shengjin Dan (Golden Victory Pill) and Jienue Dan (Malaria-Cutting Pill) is largely due to the mistaken use of Shi. According to Wang Zijing's "Jingxi Tie," the depth of toxicity of Shi is suspicious. Those who enjoy taking Hanshi San (Cold Food Powder) often develop carbuncles and sores, hence it is considered highly suspicious. Its toxicity is fierce, acting on mercury faster than any other substance, thus it is listed as an immortal medicine in *Danfang*. In mountains where Shi exists, grass does not grow in spring, and snow does not accumulate in winter. Mice die after eating it, while silkworms become fat after consuming it. The suitability and taboos of these creatures are inexplicable. Specifically produced Shi comes in varieties such as pale white, purple-peach-blossom color, gold stars, and silver stars, all with similar toxicity. Only that found in gold veins, named Woxue Shi (Snow-Holding Stone), is warm and non-toxic, distinctly different from the aforementioned types.

It originates from Xinzhou, hence also known as Xinshi.

Bitter, pungent, extremely hot, highly toxic. Those with a white color and yellow halo are called Jinjiao Pi (Gold-Footed Arsenic); those refined are called Pisuang (Arsenic Frost).

Those with red color are of the poorest quality and unsuitable for medicinal use. It is feared by mung bean sprouts, tea, and cold water. For medicinal use, it is boiled with vinegar, or used together with bud tea, or ground with soaked raw mung beans to mitigate its toxicity. For poisoning, fresh sheep blood can detoxify it, and copious amounts of cold water can also resolve it. If strong liquor is ingested, it is incurable.

[Invention] Pisuang is commonly used by malaria patients; upon ingestion, vomiting and diarrhea occur simultaneously. After vomiting, if extreme thirst occurs, mung bean soup should be given. Pisuang is highly toxic; accidental ingestion leads to death. Why use a potentially fatal drug to treat a disease that is not necessarily fatal? Is this not dangerous? However, for manic and delirious diseases, it is essential. When used in Shengjin Dan, it is invariably effective. When used in Kuzhi San (Hemorrhoid-Withering Powder) combined with Tianlinggai (Skull Cap), the hemorrhoids wither and fall off naturally after seven days. This utilizes the hot and toxic nature of Pisuang to wither bad flesh, while Tianlinggai penetrates the bone marrow, disperses old filth, and promotes muscle growth.