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Under the entry for "Silver" (Yin) in *Bencao Gangmu* (Compendium of Materia Medica), "Wu Yin" (Black Silver) is appended. It states that silver is fumigated with Sulfur (Liu Huang, 硫黄) until it turns black, thereby producing Wu Yin. Health-preservers craft vessels from this material to collect dew for drinking, which is believed to prolong life and ward off evil influences. The text only records its efficacy as a dietary supplement and does not mention its use in treating diseases. Therefore, I consulted secret prescriptions from my medical kit to supplement this omission.

It treats Fan Wei (Rebellious Stomach / Cardiac Spasm) with miraculous effect. Take one qian two fen of Wen Yin (Patterned Silver) and one jin of Sulfur. Divide the Sulfur into one hundred and twenty small packets. Obtain one large Qing Yin Guan (Pouring Silver Pot). Place the silver inside the pot, heat it over charcoal fire, and throw the Sulfur packets into the pot one by one until all the Sulfur is consumed. Retrieve the silver and grind it into powder. For the first dose, take three fen; for the second dose, two fen; for the third dose, one fen. Add three fen each of Ding Xiang (Clove), Hui Xiang (Fennel), Huo Xiang (Patchouli), and Chen Xiang (Agarwood), and one fen of She Xiang (Musk). Divide this mixture into three doses. For each dose, take two fen of silver powder, add one zhong (cup) of water, and decoct until half a zhong remains. Swallow the silver powder on an empty stomach. Complete the course over three days; upon finishing, the disease will be cured.

Recorded by Zhai Yunchuan: Zi Mu Xuan (Mother-Child Suspension) originates from lead mines in Guizhou and is formed from the essence of lead. Large pieces can weigh dozens of jin. When freshly carved and used as a washbasin for washing the head, face, and hair, it prevents graying even in old age, brightens the eyes, removes scars and moles, and moisturizes the skin and complexion. For anyone with purple-black spots on the face, long-term bathing with water from this vessel will completely remove them.
Detoxification: Removes warts, polyps, and flesh tags; darkens hair; brightens eyes.

Another name for this substance is You (Glaze). This is the residue from melting silver at a silver-smelting shop. When melting silver into a pot, one must use excessive amounts of Xiao Shi (Niter), Peng Sha (Borax), and Huang Sha (Yellow Sand) to remove impurities such as lead and copper, resulting in pure Wen Yin. The black dregs remaining at the bottom of the pot are named You. It is toxic and must not be ingested mistakenly; ingestion can cause the substance to fall and damage the intestines. This material has no medicinal application, which is why *Bencao Gangmu* appended "Wu Yin" under "Silver." Although Wu Yin lacks specific therapeutic indications, its name is still listed. As for You powder, it may have been excluded due to its toxicity. If someone accidentally ingests it, they should urgently drink two tea cups of yellow mud water to detoxify. Alternatively, one can form four liang of Yi Tang (Maltose) into small pills and swallow them occasionally with Sesame Oil (Zhi Ma You, 芝麻油). This will expel the toxin through defecation. One must continue this regimen for over a hundred days to avoid complications. *Jingyan Guangji* (Extensive Collection of Experienced Prescriptions) records that those who have ingested Yin You Shui (Silver Glaze Water) can be cured by administering Wumei Tang (Dark Plum Decoction). Yang Chunya’s verified prescription: For accidental ingestion of Yin You, eat dozens of green persimmons with the peel. In winter, eating persimmon cakes with Cigu juice (Cibula Juice) can also detoxify; this is highly effective.

Treating Tinea (Xuan): *Jiushi Qingnang* (Green Bag of Saving the World) records: For stubborn tinea, use an arbitrary amount of Yin You. Place it in a porcelain dish and set it outdoors. Tilt the dish slightly so that the Yin You absorbs dew.

*Neifu Wanying Gao* (Imperial Palace Universal Ointment): Obtained by Chen Shuidong from Cixi. Use one jin of Yin You and two jin of Black Sesame Oil. First, soak the Yin You in the oil for ten days, then crush it. Simmer together with the oil until it reaches forty to fifty percent maturity. Filter out the Yin You using a silk bag. Add one jin of Dong Dan (Red Lead) that has been stir-fried and refined (Fei Jing). Boil until it forms an ointment. This treats all kinds of unnamed swellings and toxins, tinea, hemorrhoids, fistulas, back carbuncles, and furuncles. A single application brings about a cure.

Wuyun Gao (Five Clouds Ointment): From *Bu Yao Liangfang* (Excellent Prescription Without Medicine). Treats Bard's Gland (Ma Dao Luo Li) and already ulcerated Scrofula (Shu Chuang). Use four liang of Yin Youzi (Silver Dregs), crush them finely. Use eight liang of Huang Dan (Lead Monoxide), refined. Use twenty liang of Xiang You (Sesame Oil). Place the sesame oil in a clay pot and warm it over fire. Once the oil is hot, throw the crushed Yin Youzi into the oil. Stir continuously with five branches: Peach, Willow, Mulberry, Locust, and Jujube. Wait until pearl-like bubbles appear on the surface, then skim off the dregs. Filter cleanly with cloth. Return the oil to the pot and slowly sift the Huang Dan into the oil while stirring constantly with the five branches. Stop when a drop of liquid forms a bead upon cooling. Remove and store. When using, do not expose to direct fire; melt it using a double-boiler method. Spread onto red satin and apply as a plaster.