Dai Zhe Shi

This drug is a mined ore, so its constituent list is a mineralogy and a contaminant load rather than a phytochemical profile. Hematite itself is very poorly soluble in water; gastric acid liberates only a small fraction as ferric and ferrous ions, which is the basis for the traditional claim that iron-bearing mineral drugs supply absorbable iron. The heaviness of the mineral, not any dissolved species, is what classical practice invokes for its downward-directing action.

Hematite is a documented arsenic host: arsenic substitutes into iron oxide and oxyhydroxide phases during ore formation, so the arsenic is intrinsic to the mineral and not a handling contaminant that washing removes. Whether a limit test exists is the practical question, and the answer is no. The drug is in the 2020 Chinese Pharmacopoeia, Volume I, as Zhe Shi, item 591 of the medicinal materials and decoction pieces; the monograph carries two identity reactions for Fe(III), thiocyanate giving blood-red and ferrocyanide giving a blue precipitate that turns brown with alkali, and a titrimetric iron assay, and that is all. There is no arsenic limit test, no lead limit and no cadmium limit for the crude drug, only the usage note that the drug contains trace arsenic and should therefore not be taken long term, plus whatever the pharmacopoeia's general chapters and its guideline on limits for exogenous harmful residues impose generically. Chronic inorganic arsenic exposure causes skin lesions, peripheral neuropathy and raised risk of skin, bladder and lung cancer, and older Chinese toxicology reports of repeated high-dose oral hematite in mice and rabbits describe lethality with congestion of lung and intestinal mucosa and hepatic necrosis, though those experiments are poorly characterised by modern standards.

These are the gangue phases of the ore and carry no attributed pharmacological action. Their proportion varies with the deposit, which is why iron assay rather than any marker compound is used to control the drug's quality.

Ore-hosted heavy metals accompany the iron phase and are not removed by the traditional calcine-and-vinegar-quench processing, which targets friability rather than purity. Because no monograph limit test exists for them in this drug, an assurance about a particular batch requires an actual ICP-MS or atomic absorption determination rather than reliance on pharmacopoeial compliance.

First record of the drug, entered as Dai Zhe and placed in the lower (xia) class of substances, the class reserved for drugs used to attack disease rather than for long-term supplementation. The name records the source: red-brown ore from Dai commandery.

Source of Xuan Fu Dai Zhe Tang, in which hematite is paired with Xuan Fu Hua to direct rebellious stomach qi downward for belching and hiccup after purgation. This remains the drug's principal formula context.

Records the standard processing: calcine until red-hot, then quench in vinegar three or seven times, grind and water-purify by levigation. The stated rationale is to temper the mineral and lead it into the blood aspect of the Liver channel.

Zhang Xichun used hematite far more heavily than earlier authors and argued for the raw, finely levigated mineral rather than the calcined form; it is a principal ingredient of his Zhen Gan Xi Feng Tang. His high doses are the origin of the large modern decoction range.