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(Shangpin, High Grade) in the *Shennong Bencao Jing* (Divine Farmer's Materia Medica).
[Correction] Merging Mangxiao (Mangxiao, crystallized sodium sulfate processed from Puxiao) and Mayaxiao (Mayaxiao, nitre crystals shaped like horse teeth) into this text.
[Names] Xiaoshipi (from *Mingyi Bielu*), Yanxiao (from *Bencao Gangmu*), Pixiao.
Su Song stated: "Xiao" is the name of the substance's essence; "Shi" denotes its hard and white nature; "Pu" signifies unrefined or unprocessed state. Because Mangxiao and Yingxiao (Yingxiao, nitre resembling white quartz) all derive from it, it is called Xiaoshipi.
Li Shizhen said: This substance dissolves upon contact with water and can dissolve other materials, hence the name "Xiao" (dissolve). It grows in saline-alkali lands, resembling fine salt. It is required to soften cattle and horse hides, hence the common names Yanxiao and Pixiao. After boiling and refining, when poured into a basin, the coarse sediment at the bottom is called Puxiao; the sharp crystals on top are called Mangxiao; the tooth-like crystals are called Mayaxiao. The *Shennong Bencao Jing* lists only Puxiao and Xiaoshi (Xiaoshi, potassium nitrate); the *Mingyi Bielu* added Mangxiao; the Song dynasty *Jiayou Bencao* added Mayaxiao. This likely stems from not realizing that Xiaoshi is Huoxiao (Huoxiao, potassium nitrate), and Puxiao is essentially Mangxiao and Mayaxiao, differing only in purity and coarseness. Various theories failed to recognize this, leading to confusion. Now, Mangxiao and Yaxiao are merged into one category.
[Collection and Explanation] The *Mingyi Bielu* states: Puxiao grows in the valleys of Yizhou, on the sunny slopes where salty water flows. It can be harvested at any time. Those with a bluish-white color are best; yellow ones harm people, and red ones kill. It also states: Mangxiao is produced from Puxiao.
Kou Zongshi said: Extracted from Puxiao, shaped like wheat awns, hence named Mangxiao.
Su Song said: By leaching Puxiao with warm water, taking the juice, and refining it until reduced by half, then pouring it into a basin, fine spikes grow overnight, thus named Mangxiao. There is also Yingxiao, which resembles white quartz, having four or five edges, crystal clear and lovely. Its therapeutic effects are the same as Mangxiao, also derived from Puxiao, but its refining method is distinct, and it is also called Mayaxiao.
Chen Cheng said: Puxiao is formed after the first collection and initial boiling, without further refinement, hence called Puxiao. It can be used to soften raw cattle and horse hides, and to test the authenticity of gold and silver. Mangxiao is made by leaching Puxiao and refining the juice again.
Li Shizhen said: Nitre is classified into three grades: those from Western Shu are commonly called Chuanxiao, of the highest quality; those from Hedong are called Yanxiao, second best; those from Hebei, Qingzhou, and Qizhou are called Tuxiao. All grow in saline-alkali lands. Locals scrape and collect them, boil the juice, and let it crystallize overnight. The shape resembles fine salt, mixed with sand and soil impurities, appearing yellowish-white. Thus, the *Mingyi Bielu* states: Yellow Puxiao harms people, red Puxiao kills. It must be re-dissolved in water, clarified to remove sediments, boiled with several radishes until cooked, the radishes removed, and the liquid poured into a basin. Overnight, it forms white crystals like ice or wax, hence commonly called Penxiao (basin nitre). Nitre from Qi and Wei regions has more base material with fine awn-like spikes on top, which is the Mangxiao mentioned in the *Mingyi Bielu*. Nitre from Chuan and Jin regions has less base material with tooth-like projections on top, forming hexagonal prisms, intricate and transparent, which is the Mayaxiao mentioned in the *Jiayou Bencao*. Resembling white quartz, it is also named Yingxiao. The base sediment of both Mangxiao and Yingxiao is collectively called Puxiao. Taking Mangxiao and Yingxiao, repeatedly boiling with radishes to remove salinity yields Tianxiao (sweet nitre). Placing these nitrates in wind and sun to evaporate moisture results in a light, white powder, known as Fenghuaxiao (weathered nitre). Boiling Puxiao, Mangxiao, and Yingxiao together with Gancao (Licorice Root), followed by sublimation in a vessel, produces Xuanmingfen (Mirabilite/Sodium Sulfate).
Tao Hongjing and various physicians of the Tang and Song dynasties did not realize that these nitrates are the same substance, differing only in purity. Confused by names, they speculated wildly without reaching a conclusion. See the correction section under Xiaoshi for details.
Puxiao (from *Shennong Bencao Jing*)
[Flavor and Nature] Bitter, Cold, Non-toxic.
The *Mingyi Bielu* states: Bitter, Acrid, Greatly Cold, Non-toxic. Refined to be white as silver, it possesses properties of cold and heat, slipperiness and astringency, acridity and bitterness, saltiness and sourness. Buried in the earth for a thousand years, it does not change.
Xu Zhicai said: Bitter, Salty, Slightly Toxic.
Li Shizhen said: The miraculous descriptions listed in the *Mingyi Bielu* actually refer to the efficacy of Xiaoshi (Potassium Nitrate). See the Xiaoshi section for details.
Li Dangzhi said: Dahuang (Rhubarb Root) and Shiwei (Pyrola Leaf) act as guides; it opposes Maijujiang.
Zhang Congzheng said: It fears Sanleng (Sparganium Rhizome).
[Indications] Treats hundred diseases, expels pathogenic cold and heat, drives out accumulations in the Six Fu organs, breaks up solidified masses and lingering growths.
Can dissolve seventy-two types of stones. Refined and ingested, it lightens the body and confers immortality (*Shennong Bencao Jing*). Treats heat accumulation of food and drink in the stomach, breaks blood stasis and obstruction, resolves retained phlegm and fullness, pushes out the old and generates the new (*Mingyi Bielu*). Treats heat distension, nourishes the stomach and aids digestion (Huangfu Mi).
Treats abdominal distension, obstruction of urination and defecation. Amenorrhea in women (Zhen Quan). Unblocks the Five Zang organs and treats hundred diseases and nodules, treats epidemic febrile diseases, headache, reduces swelling and detoxifies, discharges pus, moistens hair and nails (Meng Shen).
Mangxiao (from *Mingyi Bielu*)
[Flavor and Nature] Acrid, Bitter, Greatly Cold, Non-toxic.
Zhen Quan said: Salty, Slightly Toxic.
[Indications] Treats accumulations in the Five Zang organs, chronic heat causing gastric closure, expels pathogens, breaks blood stasis, resolves phlegm-solidities and knotting in the abdomen, unblocks meridians, promotes urination and defecation and menstruation, breaks five types of strangury (Lin syndrome), pushes out the old and generates the new (*Mingyi Bielu*). Treats scrofula, jaundice, epidemic heat stagnation, dissipates evil blood, induces abortion, applies externally to lac poisoning (Zhen Quan).