Xiao Shi硝石
Nitrum · Potassium Nitrate · Saltpetre · Huo Xiao · Yan Xiao
Overview
- · — internal use obsolete.*
The crystalline mineral of the classical materia medica also called and: chemically potassium nitrate, the oxidiser in black powder. Bitter, salty and warm, and marked. The classics used it to break up hard accumulation, to move water and stool downward, and applied it to red eyes, sore throat and toxic sores.
It appears in the Jin Gui Yao Lue as half of Xiao Shi Fan Shi San 硝石矾石散, prescribed for a jaundice pattern the text calls. That internal use is obsolete. Nitrate is converted in the body to nitrite, which turns haemoglobin into a form that cannot carry oxygen, and the mineral is also a powerful oxidiser with real fire and explosion hazards during handling. What survives is a narrow external role, and even that is largely displaced by better options. Read this entry as a record of a classical drug, not as a treatment recommendation.
Nature & Flavor
Bitter, salty · Warm · ToxicChannels
Heart · SpleenTypical Dosage
Internal use is obsolete. The classical internal amount was about 1.5–3 g in pills or powder, recorded here only to explain what the old formulas meant; it is not dispensed. External use in a small compounded amount, dissolved, applied to the affected area. Never taken as a self-directed remedy in any form.Actions
4 core actions
- Broke up hard accumulationFixed abdominal masses and hard accumulation in the classical record — Xiao Shi Fan Shi San 硝石矾石散, with alum, for the jaundice pattern of the Jin Gui Yao Lue. Historical; jaundice today requires diagnosis of its cause.
- Moved water and stool downwardUrinary blockage, stones and constipation, classically. Obsolete internally, and displaced by safer herbs and by medical treatment of the underlying problem.
- Resolved toxin, reduced swellingRed, swollen eyes, sore and blocked throat, and toxic sores, applied externally as a dissolved wash or paste — the one role that has any continuity, and even here it is now rarely chosen.
- Not the same drug as Mang XiaoThis is a dispensing hazard worth stating on its own. Xiao Shi is potassium nitrate; Mang Xiao (also,) is hydrated sodium sulfate, the ordinary purgative. The names are nearly identical in old texts and the minerals look alike, but they are chemically unrelated and behave differently in the body. Confirm which one a prescription means before anything is weighed.
In Formulas
Formulas containing Xiao Shi
No published formula lists this herb yet — the library is growing.
Indications & Clinical Uses
- Historical: fixed abdominal accumulation and the jaundice pattern
- Historical: urinary blockage, stones, constipation
- Limited external use: red swollen eyes, sore throat, toxic sores
- No current internal indication. Nothing in this entry describes present-day practice.
Western Medical Keywords
Searchable condition terms
Contraindications
Cautions
Xiao Shi is potassium nitrate. It is toxic, its internal use has been abandoned, and it is a strong chemical oxidiser with a fire and explosion hazard. This entry is a record of the classical materia medica, not a treatment recommendation.
- Nitrate poisoning. Swallowed nitrate is reduced to nitrite in the gut, and nitrite converts haemoglobin to methaemoglobin, which cannot carry oxygen. The result is blue-grey discolouration of the lips and skin, headache, dizziness, breathlessness, a racing heart, falling blood pressure, and in severe cases collapse and death. Infants and small children are far more susceptible than adults, and there is no safe household dose.
- Gut injury and other effects. Large amounts are corrosive to the stomach and intestines, causing vomiting, abdominal pain and bloody diarrhoea, and can injure the kidneys. Nitrate can also react with amines in the diet to form nitrosamines, which are carcinogenic.
- Fire and explosion. Potassium nitrate is an oxidiser and one of the three components of black powder. It must never be ground, mixed or stored with sulphur, charcoal, sugar, or any organic or combustible material, and it must not be heated. A mortar that has held it must be cleaned before other work. This is a genuine hazard in a dispensary, not a curiosity.
- Do not confuse it with Mang Xiao. Xiao Shi is potassium nitrate; Mang Xiao is sodium sulfate. Substituting one for the other is a real and dangerous dispensing error, and old texts make the names easy to mix up.
- Absolutely avoid in pregnancy and breastfeeding, in infants and children, in anaemia or any condition affecting haemoglobin, in G6PD deficiency, in kidney impairment, and in the frail.
- Suspected poisoning is an emergency. Blue-grey lips or fingertips after swallowing a nitrate salt means methaemoglobinaemia until proven otherwise. Call emergency services and name the substance — there is a specific antidote given in hospital.
- Regulatory note. Potassium nitrate is widely available as a fertiliser and food preservative and is not a controlled substance, which makes it easy to obtain and correspondingly easy to misuse. Availability is not permission: it has no place as a self-administered internal medicine.
Contraindicated in pregnancy: Contraindicated in pregnancy and while breastfeeding. Nitrate crosses the placenta, fetal and infant haemoglobin is especially vulnerable to being converted to methaemoglobin, and the herb's classical action of breaking accumulation is itself a reason to avoid it. There is no acceptable dose in either setting.
For licensed practitioners’ reference only
References
- Shen Nong Ben Cao Jing《神农本草经》(classical source, public domain), where it appears as 消石.
2. Jin Gui Yao Lue《金匮要略》— Xiao Shi Fan Shi San (classical source, public domain).
3. Bensky, Clavey & Stöger. Chinese Herbal Medicine: Materia Medica, 3rd ed.
4. Nitrate-induced methaemoglobinaemia and its treatment are described in standard clinical toxicology references.
5. Potassium nitrate is classified as an oxidising agent; handling and storage precautions are set out in standard chemical safety data.
Professional reference notice. Entries are scholarly references for licensed TCM practitioners and students — not medical advice, and not a recommendation to self-prescribe. Chinese herbal formulas should be used under the guidance of a qualified practitioner. Content is an original editorial compilation by Cura x Cura, cross-checked against the cited references.