朴硝，味苦、辛、咸，气寒，降也，阴也，有毒。青白者佳，黄赤杀人。诸石药毒能化，
六
腑积聚堪祛。润燥粪，推陈致新。消痈肿，排脓散毒，却天行疫痢，破留血闭藏，伤寒发狂
，停痰作痞。凡有实热，悉可泻除。又善堕胎，孕妇忌用。
芒硝，即朴硝之再煎者。消痰癖，通月经延发，漆疮可敷，难产子胞可下，洗心肝明目，
涤肠胃止疼，经云∶热淫于内，治以咸寒，佐以苦寒。仲景夫子所以用大黄、芒硝相须为使
也。
皮硝，乃硝皮而出之者也。只可用之以洗目，则老眼可复明，洗阴囊可以去湿，洗痔疮
可以
却疼，余无可用。
玄明粉，微祛虚热，亦消老痰。以上四味，除皮硝乃外治之药，余俱内治之药也。硝性
最紧
，朴硝第一，芒硝次之，玄明粉又次之，俱宜救急而不可救缓，以之治实病则宜，以之治虚
病则失。虽玄明粉能退虚热，似可治虚，然亦只可暂治虚热，而不可久治虚热也。
或疑朴硝不可用，用芒硝以佐大黄，似乎平善矣，而用之不得当，往往杀人。不识单用
大黄
而不用硝石，亦可乎？曰∶大黄，下药也。用大黄，似可不用芒硝，然而伤寒之邪传在脏中
，常有一刻不可再停之势。大黄不得芒硝，则其势不速，非好用芒硝也。用芒硝以助其迅扫
之机，邪去而正始存，安可徒用大黄而不用硝石哉。
或问芒硝佐大黄，其势更急，使大黄迅逐趋下，吾恐邪气反不尽去也。曰∶邪在上焦，
用药
宜缓；邪在下焦，用药宜急。肠中既有硬粪，不迅逐趋下，则谵语能定乎？子疑芒硝佐大黄
，虑其势甚急，而余犹恐其不急，致邪之不去也。
或问芒硝佐大黄，不过助其急也，岂别有义乎？曰∶芒硝佐大黄，亦能制大黄之猛。盖
大黄
性速，而芒硝之性更紧于大黄。大黄转不敢恃其威，而过于逐北，反有彼此牵制之益，故功
成更神也。
或问芒硝佐大黄而成功，岂不能佐大黄而致败，何子但言其功，不言其过乎？曰∶嗟乎。
孟
贲、乌获之将，骁勇绝伦，用之不得其宜，有不跋扈者乎。唯是宜用而用之耳。用之得宜，
则成功于扫荡。用之不得其宜，则致败于崩摧。谁谓芒硝但有功而无过哉。
朴硝，味道苦、辛、咸，性质寒凉，具有沉降作用，属于阴类，有毒性。颜色青白者品质较好，黄赤色的会致人死亡。它能化解各种石药引起的中毒，能够祛除六腑中的积聚病证。它能润燥通便，推陈出新。能消除痈肿，排出脓液并散解毒素，治疗天行疫痢（流行性疫病腹泻），破除停滞的瘀血和闭藏之症，治疗伤寒引起的发狂症状，以及痰饮停滞导致的痞块。凡是体内有实热证的，都可以用它来泻除。此外，它善于堕胎，孕妇禁止使用。
芒硝，就是经过再次煎煮加工后的朴硝。它能消除痰癖（痰饮积聚形成的癖块），通调月经延期不来的病症，漆疮可以用它外敷，难产时可使子胞（胎盘）下行，清洗眼睛可以明目，洗涤肠胃可以止痛。经书说：“热邪淫溢于内，用咸寒性质的药物来治疗，辅以苦寒性质的药物。”张仲景先生因此将大黄与芒硝配合使用，互为辅助。
皮硝，是从硝皮中提取出来的硝石。只可用于清洗眼睛，这样老花眼可以恢复视力，清洗阴囊可以去除湿气，清洗痔疮可以缓解疼痛，除此之外没有其他用途。
玄明粉，能轻微祛除虚热，也能消除陈旧性的痰饮。以上四种药物中，除了皮硝是外用药物外，其余都是内服药物。硝石的药性最为峻急，其中朴硝最烈，芒硝次之，玄明粉又次之，都适宜用于急救而不适用于缓治，用来治疗实证适宜，用来治疗虚证则失误。虽然玄明粉能退虚热，看似可以治疗虚证，但也只能暂时治疗虚热，而不能长期治疗虚热。
有人怀疑朴硝不可使用，用芒硝来辅助大黄，似乎比较平和了，但如果使用不当，往往会导致死亡。不知道单用大黄而不用硝石，可以吗？回答说：大黄是泻下药。使用大黄，似乎可以不用芒硝，然而伤寒的病邪传入脏腑中，常常有一种一刻也不能再停留的紧迫形势。大黄如果没有芒硝的配合，那么攻下的势头就不够迅速，这并不是喜欢用芒硝，而是用芒硝来帮助其迅速扫荡病邪的机制，邪气去除后正气才能保存，怎么能只单用大黄而不用硝石呢？
有人问：芒硝辅助大黄，药势更加急迫，促使大黄迅速向下驱逐，我担心邪气反而不能完全去除。回答说：邪气在上焦，用药宜缓和；邪气在下焦，用药宜急迫。肠道中既然已经有干硬的粪便，如果不迅速向下驱逐，谵语（神志不清、胡言乱语）的症状能停止吗？你担心芒硝辅助大黄导致药势过急，而我反而担心药势不够急，导致邪气无法去除。
有人问：芒硝辅助大黄，不过是帮助其药势急迫罢了，难道另有深意吗？回答说：芒硝辅助大黄，也能制约大黄的猛烈。因为大黄药性迅速，而芒硝的药性比大黄更峻急。大黄反而不敢依仗自己的威力，而过度地追逐败敌（过度攻下），反而有了彼此牵制的益处，所以功效更加神奇。
有人问：芒硝辅助大黄而成功，难道不能辅助大黄而导致失败吗？为什么您只说它的功效，不说它的过失呢？回答说：唉。孟贲、乌获这样的将领，骁勇绝伦，如果使用不得当，难道不会有跋扈失控的情况吗？只是在于是否应该使用以及如何正确使用罢了。使用得当，就能在扫荡病邪上取得成功；使用不得当，就会在崩摧（身体崩溃）中导致失败。谁说芒硝只有功劳而没有过失呢？
Puxiao (Mirabilite), with a bitter, acrid, and salty taste, is cold in nature, descending, yin in category, and toxic. Those that are greenish-white are superior, while those that are yellow or red can be fatal. It can dissolve the toxicity of various mineral drugs and is capable of dispelling accumulations in the six fu organs. It moistens dryness and unblocks feces, pushing out the old to bring forth the new. It dissipates carbuncles and swellings, expels pus and scatters toxins, treats epidemic dysentery (Tianxing Yili), breaks stagnant blood and closure conditions, treats mania caused by Shanghan (Cold Damage), and resolves phlegm retention leading to epigastric fullness. For all cases of excess heat, it can be used to purge them. Furthermore, it is good at inducing abortion, so pregnant women should avoid its use.
Mangxiao (Refined Mirabilite) is Puxiao that has been re-boiled. It dissipates phlegm癖 (phlegm accumulation forming masses), regulates delayed menstruation, can be applied externally for lacquer dermatitis, facilitates the expulsion of the placenta in difficult labor, washes the heart and liver to brighten the eyes, cleanses the intestines and stomach to stop pain. The Classics state: "When heat invades internally, treat with salty-cold substances, assisted by bitter-cold substances." Therefore, Master Zhang Zhongjing uses Dahuang (Rhubarb) and Mangxiao together as mutual assistants.
Pixiao (Crude Mirabilite from skin processing) is extracted from nitre skins. It can only be used to wash the eyes, restoring vision in old age; washing the scrotum removes dampness; washing hemorrhoids relieves pain. There are no other uses for it.
Xuanmingfen (Calcined Mirabilite) slightly dispels deficiency heat and also eliminates chronic phlegm. Among the above four substances, except for Pixiao which is an external treatment drug, the rest are internal treatment drugs. The nature of niter is most astringent and urgent; Puxiao is the strongest, Mangxiao is next, and Xuanmingfen is the weakest. They are all suitable for emergency situations but not for chronic conditions; they are appropriate for treating excess diseases but inappropriate for treating deficiency diseases. Although Xuanmingfen can reduce deficiency heat, seemingly allowing it to treat deficiency, it can only temporarily treat deficiency heat and cannot be used long-term for this purpose.
Some doubt whether Puxiao should be used. Using Mangxiao to assist Dahuang seems milder, yet improper use often leads to death. Is it possible to use Dahuang alone without Nishi (Niter)? I reply: Dahuang is a purgative. Using Dahuang, one might think Mangxiao is unnecessary. However, when Shanghan pathogens transmit into the zang organs, there is often a momentum that cannot be delayed for even a moment. Without Mangxiao, Dahuang's downward driving force is not rapid enough. This is not because Mangxiao is preferred, but because Mangxiao assists in the mechanism of rapid sweeping. Once the pathogen is gone, the healthy qi is preserved. How can one merely use Dahuang without Niter?
Someone asks: Mangxiao assisting Dahuang makes the momentum more urgent, causing Dahuang to rapidly drive downwards. I fear the pathogenic qi will not be completely eliminated. I reply: When pathogens are in the upper jiao, medication should be gentle; when pathogens are in the lower jiao, medication should be urgent. Since there are hard feces in the intestines, if they are not rapidly driven down, can delirium be resolved? You suspect that Mangxiao assisting Dahuang creates excessive urgency, whereas I fear the lack of sufficient urgency, leading to the failure to eliminate pathogens.
Someone asks: Mangxiao assisting Dahuang merely helps accelerate the action; is there any other meaning? I reply: Mangxiao assisting Dahuang also controls the ferocity of Dahuang. Dahuang's nature is rapid, but Mangxiao's nature is even more astringent and urgent than Dahuang's. Dahuang dares not rely on its power to chase the enemy too far, resulting in mutual restraint benefits, thus achieving miraculous efficacy.
Someone asks: If Mangxiao assisting Dahuang leads to success, can it not lead to failure? Why do you only speak of its merits and not its faults? I reply: Alas. Generals like Meng Ben and Wu Huo are peerlessly brave. If used improperly, will they not become insubordinate? It is simply a matter of using them when appropriate. Used appropriately, success is achieved in sweeping away pathogens. Used inappropriately, failure results in collapse. Who says Mangxiao has only merits and no faults?