一名青盐。补肾、泻血热。
甘咸而寒。入肝肾。助水脏。平血热。治目痛赤涩。（散肝经风热。）吐血溺血，齿舌出
血，
坚骨固齿。（擦牙良。）明目乌须。功同食盐而更胜之。出西羌。不假煎炼。方棱明莹色青者
良。（风眼烂弦、戎盐化水点之。）
泻热。
辛咸大寒。治时气热盛。口渴水肿。盐精渗入土中。年久结成。清莹有棱。入水即化。
亦名
寒水石。（古方所用寒水石、是凝水石、唐宋诸方用寒水石、即石膏。）
泻热救阴。
太阴之精。咸寒而降。治上盛下虚。救阴助阳。（同硫黄、硝石用。）有扶危拯逆之功。
（正
阳丹、用治伤寒壮热、来复丹、用治伏暑热泻。）出解池。通泰积盐处。咸卤所结。青白莹
彻。片皆六棱者良。（今世用者、多是绛石。）
即皮硝。大泻、润燥、软坚。
芒硝、辛能润燥。咸能软坚。苦能下泄。大寒能除热。朴硝、酷涩性急。芒硝、经炼稍
缓。
能荡涤三焦肠胃实热。推陈致新。（与大黄同、盖邪气不除、正气不能复也。）治阳强之病。
伤寒。（经曰∶人之伤于寒也、必病热、盖寒郁而为热也。）疫痢。积聚结癖。留血停痰。黄
疸淋闭。瘰 疮肿。目赤障翳。通经堕胎。（经疏云∶硝者消也、五金八石、皆能消之、况
脏腑之积聚乎、其直往无前之性、所谓无坚不破、无热不荡者也、病非邪实深固、闭结不通
、不可轻投、恐误伐下焦真阴故也、无己曰∶热淫于内、治以咸寒、气坚者以咸软之、热盛
者以寒消之、故仲景大陷胸汤、大承气汤、调胃承气汤、皆用芒硝以软坚去实热、结不至坚
者、不可用也、佐之以苦、故用大黄相须为使、按芒硝消散、破结软坚、大黄推荡、走而不
守、故二药相须、同为峻下之剂、好古曰∶本草言芒硝堕胎、然妊娠伤寒可下者、兼用大黄
以润燥、软坚、泻热、而母子相安、经曰∶有故无殒、亦无殒也、此之谓欤、谓药自病当之
、故胎无患也。）硝能柔五金。化七十二石为水。生于卤地。刮取煎炼。在底者为朴硝。在
上者为芒硝。有牙者为马牙硝。置风日中。消尽水气。轻白如粉为风化硝。大黄为使。（本
经别录、朴硝、硝石虽分二种、而气味主治略同、后人辨论纷然、究无定指、时珍曰∶朴硝
下降、属水性寒、硝石为造炮焰硝、上升、属火性温。）
[Rongyan (Roc Salt)]
Also known as Qingyan (Green Salt). It tonifies the Kidney and clears Blood-heat.
It is sweet, salty, and cold in nature. It enters the Liver and Kidney meridians. It assists the Water Organ (Kidney), calms Blood-heat, and treats eye pain with redness and dryness. (It disperses Wind-heat from the Liver meridian.) It treats hematemesis (vomiting blood), hematuria (blood in urine), bleeding from teeth and tongue, strengthens bones and teeth (effective for brushing teeth), brightens the eyes, and darkens hair. Its efficacy is similar to common salt but superior. It originates from the Western Qiang region. It does not require boiling or refining. Those that are square-edged, transparent, crystal-clear, and greenish in color are of good quality. (For wind-eye with ulcerated eyelid margins, dissolve Rongyan in water and apply as drops.)
[Puxiao (Crude Saltpeter)]
It purges heat.
It is acrid, salty, and extremely cold in nature. It treats epidemic Qi with excessive heat. It treats thirst and edema. Salt essence seeps into the soil and crystallizes over years. It is clear, pure, and edged; it dissolves immediately upon contact with water. It is also called Hanshuishi (Cold Water Stone). (The Hanshuishi used in ancient prescriptions refers to Ningshuishi (Condensing Water Stone); the Hanshuishi used in Song and Tang dynasty prescriptions is actually Shigao (Gypsum Fibrosum).)
It purges heat and saves Yin.
It is the essence of Taiyin. It is salty and cold, with a descending nature. It treats excess above and deficiency below. It rescues Yin and assists Yang. (Used together with Liuhuang (Sulfur) and Xiaoshi (Niter).) It has the merit of supporting critical conditions and reversing adverse situations. (Zhengyang Dan is used to treat severe fever in Shanghan [Cold Damage]; Laifu Dan is used to treat summer-heat retention with diarrhea.) It originates from Jiechi, an area where salt accumulates in Tongtai. It forms from saline brine. Those that are greenish-white, transparent, and crystalline, with six-edged flakes, are of good quality. (What is commonly used today is mostly Jiangshi [Red Stone].)
[Mangxiao (Refined Saltpeter)]
It is the same as Pixiao (Skin Saltpeter). It strongly purges, moistens dryness, and softens hardness.
Mangxiao: Acridity moistens dryness; saltiness softens hardness; bitterness drains downward; extreme cold eliminates heat. Puxiao is harsh, astringent, and acts swiftly; Mangxiao, after refining, acts more mildly. It can cleanse the Sanjiao (Triple Burner) and intestines/stomach of excess heat, pushing out the old to bring forth the new. (When used with Dahuang [Rhubarb], because if pathogenic factors are not eliminated, healthy Qi cannot recover.) It treats Yang-excess conditions. Shanghan [Cold Damage]. (The Classic states: When humans are injured by Cold, they inevitably develop heat, because Cold stagnates and transforms into heat.) Yi li (Epidemic dysentery). Accumulations and masses. Retained Blood and stagnant Phlegm. Jaundice, Lin syndrome (dysuria), and urinary obstruction. Luoli (scrofula) and sores/swellings. Red eyes and cataracts. Unblocks menstruation and induces abortion. (Bencao Jing Shu states: Xiao means to eliminate. It can eliminate the five metals and eight stones, let alone accumulations in the Zang-Fu organs. Its nature charges forward unimpeded, described as "nothing is too hard to break, no heat is too great to purge." If the disease is not characterized by deep-seated pathogenic excess and blockage, it should not be lightly administered, lest it damage the True Yin of the Lower Jiao. Wuji stated: When Heat dominates internally, treat with salty-cold methods; use saltiness to soften firmness; use cold to eliminate excess heat. Therefore, Zhang Zhongjing's Da Xianxiong Tang, Da Chengqi Tang, and Tiaowei Chengqi Tang all use Mangxiao to soften hardness and remove excess heat. If the accumulation is not hard, it should not be used. Assisted by bitter herbs, hence Dahuang is used as an assistant. Analysis: Mangxiao dissipates, breaks knots, and softens hardness; Dahuang pushes down, moves without staying put. Thus, these two drugs synergize as potent purgatives. Haoguo stated: Materia Medica records that Mangxiao causes abortion. However, in pregnancy complicated by Shanghan requiring purgation, using Dahuang concurrently to moisten dryness, soften hardness, and purge heat ensures safety for both mother and fetus. The Classic states: "If there is a cause [pathology], there will be no injury," meaning the drug targets the pathology, thus sparing the fetus.) Xiao can soften the five metals and dissolve seventy-two types of stones into water. It grows in saline lands. It is scraped and refined. The substance settling at the bottom is Puxiao; the substance floating on top is Mangxiao. Those with crystalline teeth-like structures are Mayaxiao (Horse-tooth Saltpeter). Placed in wind and sun until moisture evaporates, becoming light and white like powder, it is called Fenghuaxiao (Weathered Saltpeter). Dahuang is used as an guiding herb. (Bencao Bie Lu notes that although Puxiao and Xiaoshi are classified as two different substances, their flavors, properties, and indications are roughly similar. Later discussions were controversial without definitive conclusion. Li Shizhen stated: Puxiao descends, belongs to Water nature, and is cold; Xiaoshi is used to manufacture explosive saltpeter, ascends, belongs to Fire nature, and is warm.)