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Is Yanxiao (Saltpeter, Natrii Sulfas), acrid, bitter, salty, warm in nature, and toxic. Melt it and add Licorice Root (Gancao) until crystallization is fixed, then take for use.

The *Shennong Benjing* states it treats a hundred diseases, eliminates cold-heat pathogenic factors, drives out accumulations, consolidations, and lingering masses in the six fu organs, and can dissolve seventy-two types of stones. (Various pharmacopoeias have misplaced this text under the entry for Puxiao [Mirabilite], but considering the ability to dissolve seventy-two types of stones, could Puxiao really achieve this?)

Innovation: Yanxiao belongs to Fire; its nature ascends. It can break up stagnation and dissipate hardness, treating various diseases characterized by mixed cold and heat; it ascends and disperses constrained fire in the Sanjiao (Triple Burner), harmonizes deficiency-cold of the zang-fu organs, eliminates cold-heat pathogenic factors, and drives out accumulated heat in the six fu organs. These effects do not exceed the indications described in the *Benjing*. The *Bielu* describes it as a supreme spiritual substance of heaven and earth that can dissolve seventy-two types of stones. Baopuzi also stated: "It can soften the five metals and dissolve seventy-two types of stones." This confirms the earlier textual misplacement. When used with Liuhuang (Sulfur), it pairs the two qi of Yin and Yang, evenly regulates Yin and Yang, and possesses the function of ascending and descending Water and Fire, treating diseases of cold, heat, slackness, and urgency. Generally, Liuhuang is warm and promoting movement, with a descending nature; Xiaoshi (Niter) is warm and dispersing, with an ascending nature. One ascends and one descends; this is the subtlety of prescription formulation.

(Sha) salty, bitter, acrid, hot in nature, and toxic. Boil with Vinegar until dry, scrape off the residue for use. Those from Panyu are superior. It fears sour plant water and avoids sheep blood. For poisoning, grind fresh Green Bean (Lüdou) into juice and drink freely to detoxify.

Innovation: Sha is extremely hot, formed from the crystallization of brine. It inherits the qi of Yin toxicity and contains the essence of Yang toxicity. In breaking up stagnation and attacking hardness, nothing surpasses it. Therefore, it treats dysphagia (Yege) and regurgitation, mass formations, and meat-like syndromes. Its property can soften gold and silver, so it is used in welding medicinal materials. The statement that it can transform the human heart into blood is an exaggeration to describe its rapid and potent action. Externally, it treats malignant flesh, removes warts, and clears nasal polyps most swiftly. However, it must not be overused; if used, wash immediately with Licorice Decoction. Observing that fake gold and silver can be dissolved when placed in a Sha pot, how much more so would long-standing dead fetuses in the human abdomen rot and disintegrate? But since its nature is toxic and fierce, if there is still vitality, do not test it lightly.

Also known as Pengsha

Sweet, slightly salty, non-toxic. Dissolve in Licorice Decoction, stir-fry over low heat until loose, then use.

Innovation: Pengsha is sweet and slightly salty, warm in temperature, white in color, and light in texture. It can clear excess heat in the chest, diaphragm, and Upper Jiao. The *Suwen* states: "When heat dominates internally, treat with salty-cold substances, using sweet flavors to moderate them," which applies here. Its property can soften the five metals and remove dirt and grease. Therefore, it primarily treats phlegm-cough and throat obstruction (Houbi). Breaking up nodules, treating dysphagia, accumulations, fishbones stuck in the throat, tubercles, and malignant flesh, it relies on its ability to soften objects. Holding it in the mouth to melt and swallow saliva treats swelling and pain in the throat and phlegm-heat above the diaphragm, relying on its ability to dissipate swelling. For eye opacities and various dental diseases, it is used for its ability to cleanse dirt. In ancient times, when treating fishbones stuck in the throat that could not be swallowed despite hundreds of attempts, holding it in the mouth and swallowing the juice resulted in immediate relief; this is evidence of its softening-hardness effect.