Library

[Puo Xiao]
Taste: bitter, pungent, salty; Nature: cold; Toxicity: toxic. Yellow Puo Xiao harms the body, and red Puo Xiao is lethal. For medicinal use, only white Puo Xiao must be selected. Dissolve Puo Xiao in water, clarify to remove dregs, add fresh juice of Raphanus sativus (radish), boil together, pour into a basin, and let stand overnight until it crystallizes like ice; this is called "Basin Nitre" (Pen Xiao). Nitre from Qi and Wei regions forms needle-like crystals on the surface, called "Mang Xiao" (Ming Nitre). Nitre from Sichuan and Shanxi regions forms hexagonal prismatic crystals on the surface, called "Ya Xiao" (Tooth Nitre). Take Mang Xiao, repeatedly refine it with radish juice to remove the salty taste, hang it in a ventilated place to blow away moisture until it becomes light and white like powder; this is called "Feng Hua Xiao" (Weathered Nitre). Boil Mang Xiao and Ya Xiao together with radish juice and Gancao (Licorice Root), then process through distillation/sublimation; this is called "Xuan Ming Fen" (Dark Bright Powder).

The *Shennong Bencao Jing* states that it treats accumulated heat in the five zang organs, stomach distension and obstruction, purges accumulated and bound food residues, pushes out the old to bring forth the new, and eliminates pathogenic factors. (This passage was previously misplaced in the entry for Xiaoshi [Niter]; it has now been corrected. A detailed analysis of treating conditions of the five zang organs reveals they are caused by fixed accumulation of heat pathogens, which Xiaoshi cannot treat.)

[Commentary]
When heat pathogens overflow within, treatment should employ salty-cold substances. Hard accumulations are softened by salty flavors, and heat is cleared by cold properties. This does not exceed the wonderful application of "pushing out the old to bring forth the new" described in the *Shennong Bencao Jing*. Zhang Zhongjing's formulas, such as Da Xianxiong Tang (Major Chest-Stagnation Decoction), Da Chengqi Tang (Major Order-the-Qi Decoction), and Tiaowei Chengqi Tang (Regulate-the-Stomach Order-the-Qi Decoction), all use Mang Xiao to soften hardness and eliminate excess. Mang Xiao possesses a slight pungency, allowing it to circulate freely without staying static. If heat accumulation is not yet hard, it should not be used lightly. For pediatric Chi You Feng (Red Roaming Wind), cloth soaked in Xiao Qing Tang (Clear-Heat Decoction) can be applied to wipe the affected area.

[Xuan Ming Fen]
Named "Bai Long Fen" (White Dragon Powder) in the *Yuyao Yuan Fang*.
Taste: pungent, sweet; Nature: slightly cold; Toxicity: non-toxic.

[Commentary]
Xuan Ming Fen is made by refining Mang Xiao multiple times and adding Gancao (Licorice Root) to moderate its salty-cold nature. It is used to treat phlegm-heat above the diaphragm, excess heat in the stomach, and retained fecal matter in the intestines. Unlike Mang Xiao, it does not have a harsh potency that damages blood and qi. However, individuals with spleen-stomach deficiency-cold or yin-deficiency with fire hyperactivity must avoid using it lightly to prevent the error of "depleting the deficient."

[Feng Hua Xiao]
Taste: sweet, salty; Nature: cold; Toxicity: non-toxic.

[Commentary]
Feng Hua Xiao has a sweet, moderating, and light-floating nature. Therefore, it is suitable for treating phlegm-heat in the upper jiao (heart and lungs) without causing diarrhea. It also treats phlegm-dampness in the meridians, proving effective for symptoms characterized by heaviness rather than soreness or pain. Zhi Mi Fu Ling Wan (Confusion-Dispelling Poria Pill) is an ideal formula for treating phlegm-dampness flowing into the yang regions of the shoulders and back, causing dull pain, but it is only suitable for individuals who are obese and have robust qi. For red and swollen eyelids, apply mixed with human milk.