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[Lunar Salt / Stone Alkali]
Also known as Shi Jian (Stone Alkali).
Bitter, salty, slightly cold, non-toxic.
The *Shennong Bencao Jing* (Divine Farmer's Materia Medica) states it treats severe heat causing polydipsia (excessive thirst), mania and irritability, eliminates pathogenic factors and gu poison, and softens the skin.
Invention: The salty taste and mobile nature of alkali enable it to resolve phlegm and grind down accumulations, dispelling heat and irritability. It is suitable for gu poison and polydipsia presenting as excess-heat syndromes. For those with rough skin, washing with hot water gradually removes stubborn scales; this is what is meant by "softening the skin." Shui Jian (Water Alkali) is made by leaching ashes from kitchen stoves with hot water and mixing them with Yinyou jiao (silver-black sediment/precipitate). Its property allows it to ferment dough, so it is used in all bakeries. However, patients who consume it often develop edema; therefore, prescriptions frequently prohibit the use of wet noodles. Observing its ability to wash away dirt on clothes reveals its strong cutting and scraping power.

[Ning Shui Shi / Congealed Water Stone]
This is Han Shui Shi (Cold Water Stone).
Acrid, salty, cold, non-toxic. Genuine specimens are extremely rare in modern times. To verify authenticity, place it in the mouth; if it dissolves immediately, it is genuine; otherwise, it is fake. Shi Gao (Gypsum Fibrosum) is also called Han Shui Shi, but it is different from this herb.
The *Shennong Bencao Jing* states it treats body fever, accumulation of pathogenic qi in the abdomen, a sensation of fire burning in the skin, and irritability/fullness.
Invention: Han Shui Shi grows beneath accumulated salt, formed by yin condensing qi; it is the essence of salt. It is a superior herb for treating excessive heat accumulating in the Heart and Kidney. The *Shennong Bencao Jing* mentions treating abdominal accumulations because the salty flavor can soften hardness. Body fever and the sensation of fire burning in the skin are treated because the salty flavor can descend fire. Feng Yin Tang (Wind-Dragging Decoction) in the *Jin Gui Yao Lue* (Essential Prescriptions of the Golden Cabinet) and Zi Xue (Purple Snow) in the *Ju Fang* (Formulas of the Bureau) both use it to treat excess pathogenic heat. If genuine specimens are unavailable, Rong Yan (Roc Salt) or Xuan Jing Shi (Mysterious Essence Stone) can be used as substitutes, primarily utilizing their salty-cold descending and purgative properties.

[Xuan Jing Shi / Mysterious Essence Stone]
Acrid, salty, cold, non-toxic. Those that are blue-white with a tortoise-shell pattern on the back are of high quality.
The *Shennong Bencao Jing* states it eliminates wind-cold pathogenic factors and damp-bi syndrome, and benefits essence and qi.
Invention: Xuan Jing Shi inherits the essence of Taiyin (Great Yin) and shares the same nature as salt; thus, its shape is hexagonal, symbolizing the number of Old Yin. The *Shennong Bencao Jing* claims its flavor is salty and its nature warm, which is a transcription error; its nature is actually cold, not warm, and its flavor is acrid-salty with a sinking and descending action. When combined with Liu Huang (Sulfur) and Xiao Shi (Niter), it treats conditions of excess above and deficiency below, consolidating Yang and assisting Yin, possessing the merit of rescuing critical conditions and reversing collapse. It is used in Lai Fu Dan (Restoration Pill), specifically taking the meaning of "one Yang returning," employing the method of "treating cold with cold," deeply grasping the mysteries of the various treatments described in the *Shennong Bencao Jing*.