Hydrargyrum oxydatum crudum — a sublimed mercuric oxide (HgO) preparation; the red form is 红升丹 and the yellow form 黄升丹
Nature and flavour. Acrid, hot; classed as strongly toxic. Lung and Spleen systems in the common account.
Not a mineral as dug but a mineral as made: mercury is heated together with saltpetre and alum in a sealed vessel and the product sublimed, which is why it is called 升药, the sublimed drug, and why the older name 三仙丹 names its three ingredients. It is one of the places where Chinese pharmacy and alchemy are plainly the same craft. Classical texts describe it as drawing out toxin, dissolving putrefaction, discharging pus and engendering flesh, and it is recorded for boils and carbuncles, for chronic ulcers and fistulae, and for promoting the separation of dead tissue from a sore. It is characteristically used as a small component of a compound powder rather than on its own. That is also how the traditional literature controls it: the drug is powerful, the amount used is minute, and the person measuring it was trained. None of those conditions exists in a household, which is why this page gives no amount and no instruction.
性味归经。辛，热；有大毒。归肺、脾经（通行说法）。
不是挖出来的矿物而是做出来的矿物：水银与硝石、白矾共置密封器皿中加热升华而得，因此名为升药，旧称三仙丹也正是点明这三味原料。这是中药与炼丹术显然为同一门手艺的地方之一。古籍记载拔毒、化腐、排脓、生肌，用于痈疽疔疮、慢性溃疡与瘘管，并促使疮面腐肉脱落。它的典型用法是作为复方散剂中的小比例成分，而不是单用。传统文献也正是以此管控它：药力峻烈、用量极微、称量者是受过训练的人。这三个条件在家庭中一个都不成立，因此本页不给任何份量，也不给任何操作说明。
一种汞化合物，而汞就是安全问题的全部。它可经皮吸收，加热产生的蒸气与粉尘则经肺吸收；汞在体内蓄积，损害并不立刻出现，这正是它的危险之处。慢性汞中毒表现为震颤、牙龈红肿出血与流涎增多、易怒与性情改变、周围神经病变以及肾损害；旧时制帽匠与制镜匠的病态是同一种中毒。若干国家已发表病例报告，记载使用含汞传统制剂（包括外用制剂）后发生汞中毒，其中有些在症状与药膏被联系起来之前已暴露相当长时间。任何情况下都不得内服。也不作自用：不宜大面积、用于破损皮肤或长期反复使用，绝不可加热。孕期与哺乳期、儿童、肾病患者一律不得使用。任何可疑接触都须就医评估，并按指征检测血汞或尿汞。