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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?