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Nixi (Salpetrae Nitrum)

Taste: Bitter, Acrid. Nature: Cold to Great Cold. Toxicity: Non-toxic. Indications: Treats accumulation of heat in the five zang organs, stomach distension and obstruction, clears away accumulated and stagnant food, pushes out the old and brings forth the new, eliminates pathogenic factors, treats one hundred and twenty diseases in the five zang organs and twelve meridians, sudden shanghan (Cold Damage), excessive heat in the abdomen, relieves irritability and fullness, treats xiaoke (Wasting-Thirst syndrome), promotes urination, and cauterizes sores. Refine into a paste. Long-term use lightens the body. This is a divine substance of heaven and earth, capable of transforming into twelve types of stones. Also known as Mangxiao (Mirabilite). Grows in valleys of Yizhou, as well as Wudu, Longxi, and Xiqiang. Harvested at any time. (Processed with fire to modify its properties; incompatible with Kushen (Sophorae Flavescentis Radix) and Kucai (Amaranthi Tricoloris Herba); fears Nüwan.)

Tao Hongjing stated: Its therapeutic effects are similar to Puxiao (Gypsum Fibrosum). The *Xian Jing* (Immortal Classic) often uses this to dissolve various stones. Currently, there are no specialists to distinguish them clearly. Recent inquiries indicate it is still called "Nixi Pu," which implies they are not the same substance. Previously, someone obtained an item whose color and texture were largely similar to Puxiao but slightly different; it felt like salt or snow when held but was not cold. When forcibly burned, purple-blue smoke rose, leaving ash behind, and it did not boil vigorously like Puxiao. It was claimed to be true Nixi.

This text also states it is another name for Mangxiao. However, current Mangxiao is made by refining Puxiao. This aligns with the later statement by Huangfu, yet neither has been rigorously verified. Efficacy testing is required for further confirmation. The method for processing Nixi is found in the *San Shi Liu Shui Fang*. Longxi, Shu, and Qinzhou are located west of Chang'an among the Qiang tribes. Today, it is found in areas with saline soil north of Dangchang. The *Tang Bencao* commentary notes: This is indeed Mangxiao. Puxiao is also called Nixi Pu. Currently, crude and inferior Puxiao is leached, the juice is extracted, and it is refined into Mangxiao, which is Nixi. The *Ben Jing* states it is another name for Mangxiao; later authors added a separate entry for Mangxiao, which is erroneous. Current annotation identifies this as Dishuang (Earth Frost). In mountains and marshes, frost forms on the ground in winter. It is swept up, leached with water, and then refined. It is named Nixi because it can dissolve various stones. It is not of the same category as Puxiao and Mangxiao merely bearing the name "Xiao." The designation "another name for Mangxiao" arises because fine acicular crystals resembling frost appear during initial refining, hence the name Mangxiao. This is entirely distinct from the subsequent entry on Mangxiao. Tao's annotations in older texts cite various evidence, likely due to inaccurate identification. These are now rejected. Ministers Yu Xi et al. according to the *Shu Bencao*: Da Huang (Rhei Radix et Rhizoma) serves as the guiding herb. Note: Current Nixi is refined from Puxiao or made from Earth Frost. It resembles hairpin legs; high-quality pieces are five fen long and can dissolve seventy-two types of stones into water, hence the name Nixi. Wu Shi stated: Nixi is the Sovereign herb; incompatible with Zengqing (Chalcanthitum); fears congee. Taste: Salty. Toxicity: Slightly toxic. Indications: Treats luoli (scrofula) of the neck, diarrhea, expels pathogens and breaks blood stasis. Another name is Mangxiao. Burning it produces Nixi. Indications: Breaks accumulations, dissipates hard knots. Also written as Kunixiao. Highly effective for abdominal distension. Nixi and Mangxiao are mostly produced by people in Chuan-Yuan; their detailed rationale should be inquired about. Ri Huazi stated: Nixi fears Xingren (Armeniacae Semen Amarum) and Zhuye (Bambusae Folium). Holding it in the mouth treats hou bi (throat closure). Authentic material undergoes the "Fu Huo" (subduing fire) method: decocted in Liuzhi Tang (Willow Twig Decoction) for three cycles. If the liquid reduces, add hot liquid; the subduing process stops.

The *Tu Jing* details are under the Puxiao entry.

Lei Gong stated: For use, first grind into powder. Place in a porcelain bottle and heat over five jin of fire until red-hot. Mix Jichangcai (Portulacae Herba) and Baiziren (Platycladi Semen) together. When the bottle is red-hot, throw the Nixi into the bottle; the Nixi will naturally undergo Fu Huo. For every four liang of Nixi, use fifteen Di Zhu Zi (unit/measure) of Jichangcai and Baiziren combined. *Shenghui Fang*: Treats red and painful eyes. Grind Nixi extremely finely. Each night before sleep, use copper chopsticks to take a amount the size of a millet seed, apply to the eye corner. Wash with salt water the next morning. *Waitai Miyao*: Treats aversion to cold with shivering, resembling impending back carbuncle, or existing round red lesions. Apply wet compresses; replace when warm. Frequent changes lead to immediate recovery. *Lingyuan Fang*: Treats the five types of lin syndrome (dysuria): Lao Lin (fatigue-type), Xue Lin (blood-type), Re Lin (heat-type), Qi Lin (qi-type), and Shi Lin (stone-type), especially severe cases. Touge San: Use one liang of pure white Nixi free of soil, raw and finely powdered. Take two qian each time. Administer according to the following decoctions for each type: Lao Lin, caused by fatigue and deficiency leading to urinary retention and lower abdominal pain; administer with Kai Zi (Abutili Semen) powder decoction. After relief, must take Buxu Wan/San (Deficiency-Nourishing Pills/Powder). Xue Lin, characterized by inability to urinate, hematuria, pain, and urgency; Re Lin, characterized by hot, red, dribbling urine and lower umbilical pain; both administered with cold water. Qi Lin, characterized by lower abdominal fullness and urgency, post-void dribbling; administered with Mutong (Akebiae Caulis) decoction. Shi Lin, characterized by penile pain, urinary retention, radiating lower abdominal distension and pain, passage of sand/stones, and syncope; first stir-fry the powder in a ding (cauldron) through paper until the paper chars, then re-grind finely, administer with warm water. Urinary retention: administer with Xiaomai (Tritici Fructus Immaturus) decoction. Sudden onset of various lin syndromes: all administered with cold water. Take on an empty stomach. First, mix the medicine until it dissolves like water, then ingest, followed by decoction. For those unresponsive to other medicines, this yields immediate cure. Chen Cangqi's *Shiyi Xu*: Severe headache relieved by insufflating Xiao Mo (Nixi powder) into the nose. *Bingbu Shouji*: For Dan Shi (mineral pill) users suffering from unbearable hot sores: encircle the swelling with a paper ring, fill the center with Nixi, and drip water over it using a spoon. Stop when heat and pain subside. *Baozang Lun*: Nixi, if subjected to grass-subduing fire without weight loss, softens hard materials like gold, silver, copper, and iron instantly. *Records of the Grand Historian · Chunyu Yi*: The Beauty of King Zichuan of Zhou could not deliver her baby. Chunyu Yi was summoned. He gave her a pinch of Langdang Yao (Datura medicine) with wine, and she delivered immediately. Yi re-examined her pulse; it was rapid, indicating residual pathology. He administered one dose of Nixi, resulting in the expulsion of bean-sized blood clots, approximately five or six pieces.

*Yanyi* stated: Nixi is the residue that condenses at the bottom after Mangxiao has been extracted during secondary refining. Having lost its essence, it is merely dregs. Thus, its efficacy is slow, primarily capable of igniting fireworks. *Tang Ben* commentary: Named Nixi because it can dissolve various stones. Subdue fire by boiling in Liuzhi Tang for three cycles; replenish the decoction as it evaporates.