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Nuxitong (Sal Nitri, Stone Nitre), also known as Huoxiao (Fire Nitre) or Yanniao (Flame Nitre); Mangxiao (Mirabilite), which is the substance formed when Xiao (Nitre) is boiled and condensed into blocks, is called Puxiao (Raw Nitre) or Pixiao (Skin Nitre). Li Shizhen stated: Puxiao acts downward, while Huoxiao acts upward. Huoxiao produces flames when exposed to fire; its nature is similar to that of Borneolum Syntheticum (Zhangnao) and distilled spirits (Huojio). The *Shennong Bencao Jing* states it is cold, while the *Mingyi Bielu* states it is extremely cold; however, in reality, it is extremely warm. Liu extended this theory, claiming that Shuixiao (Water Nitre, i.e., Mangxiao) treats heat accumulation. Heat accumulation mostly belongs to the Blood level, described as "Yin fails to descend, Yang fails to transform." It can move the Yang accumulation within Yin, causing Yin to descend and Yang to transform naturally. Huoxiao treats heat stagnation, which mostly belongs to the Qi level, described as "Yang fails to ascend, Yin fails to flow smoothly." It can penetrate the Yin stagnation within Yang, causing Yang to transform and Yin to flow smoothly. Zou further interpreted Huoxiao as having a nature tending toward Yang, capable of resolving intense heat arising from Yin transforming into Yang; whereas Shuixiao has a nature tending toward Yin, thus expelling solid accumulations hidden within Yang. These three scholars can be said to have uncovered insights previously unmentioned by predecessors. Nevertheless, I privately feel uneasy about this. The principles of Yin and Yang are subtle; discussing substances in isolation makes it easy to rationalize arguments. However, integrating substances with clinical manifestations and formulas makes it difficult to be precise and thorough. Speaking generally may seem profound, but is it not better to speak specifically and plainly? Huoxiao indeed ascends and disperses, acting on the Qi level, but what it ascends and disperses is the Qi of heat stagnation within Yin, not heat stagnation within Yang. Diseases in Yin meridians or Yin organs are Yin; diseases caused by Yin pathogens are also Yin. Generally, because its acrid-warm nature reaches the upper body and its salty-bitter nature enters the lower body, it treats diseases both above and below, ultimately归结ing to resolving heat stagnation within Yin. Liu's phrase "penetrating Yin stagnation within Yang" is perhaps still debatable. Examining clinical cases, Laifu Dan, Erqi Dan, and Yuzhen Wan all treat latent heat within Yin pathogens; Xiaoni Shi Fanshi San in the *Jingui Yaolue* is particularly evident. Only Dahuang Xiaoshi Tang uses purgation to drain downward, which seems contrary to the principle of ascending and dispersing. However, its symptoms include jaundice, abdominal fullness, difficulty urinating, and red face. Heat is a Yang pathogen; it stagnates due to dampness and resides solely in the interior. With interior excess and resolved exterior, this is also a pathogen of Yin. How else can one enter such Yin pathogens without salty and bitter flavors? Discarding Mangxiao for Xiaoshi is because although there is sweating at the exterior, damp-heat remains between the tissues. Xiaoshi is more acrid-warm than salty-bitter; therefore, among the purgative agents like Dahuang, Huangbai, and Zhizi, adding this ingredient helps reach the exterior and disperse pathogens. The difficulty in understanding Huoxiao lies in its use of warmth to treat heat. Regarding Shuixiao using coldness to treat heat, stating it enters the blood, moistens downward, softens hardness, and breaks accumulations has been consistent since ancient times. Yet, is it truly easy to understand? Dachengqi Tang, Tiaowei Chengqi Tang, and Taohe Chengqi Tang certainly remove heat accumulations in the blood. However, only Daxiexiong Tang/Wan uses a large amount of Mangxiao (one to half a sheng) to treat Jie Xiong (Chest Binding). Even if one claims it breaks accumulations and softens hardness, requiring large doses, does one not worry that heavy descending agents might accelerate their descent too quickly? There is a reason. Mangxiao is the substance condensed at the top during the boiling process of Nitre. Its fine crystals are sharp, its texture is lighter than Puxiao, and its taste includes acridity. Does it not possess an ascending nature? Does it not enter the Qi level? Later generations even used it to treat heat syndromes of the mouth, tongue, throat, and pharynx. Can we say Mangxiao cannot reach the upper body to treat upper disorders? From this perspective, Liu's theory of "Yang accumulation within Yin" seems questionable. Zhongjing said, "When a disease originates in Yang and is incorrectly treated with purgation, heat enters and causes Chest Binding." Based on this, it is clearly not Yang accumulation within Yin. Furthermore, all formulas by Zhongjing using Mangxiao treat Yang syndromes without latent Yin. Formulas using Xiaoshi involve both Yin and Yang within a single syndrome. Thus, moving Yang accumulation within Yin is done by Xiaoshi, not Mangxiao. Mangxiao expels heat accumulations in Yang syndromes. Mangxiao is salty and cold, surpassing bitter and acrid; prolonged boiling accelerates its descent. Rapid descent leaves pathogens in the upper body; hence, Zhongjing always adds it later, boils briefly, and stirs gently. Xiaoshi is acrid and warm, surpassing salty and bitter; brief boiling accelerates its ascent. Rapid ascent prevents it from entering the lower body; hence, Zhongjing boils two shengs down to one sheng to slightly restrain it. These two substances seem to oppose each other. Liu also seemed to interpret them as opposites, but he was mistaken. Salty and cold are both Yin; its slight acridity merely carries an ascending property and cannot treat Yin pathogens. Salty and warm represent different Yin-Yang orientations. Warmth combined with acridity, and acrid-warmness combined with moistening, applies only to syndromes where Yang pathogens exist within Yin. The profound meaning here is not easily grasped suddenly; thus, it is not a simple opposition. Moreover, does Liu consider entering the blood level as being within Yin? If the blood level is Yin, then Dachengqi Tang should be termed Taiyin Disease, not Yangming Disease. Taohe Chengqi Tang should be Shaoyin Disease, not Taiyang Disease. Mangxiao is likely a blood-invigorating agent but does not exclusively enter the blood; it resembles Dahuang significantly. Dahuang is bitter, enters the Heart, and opens heat accumulations in the chest and diaphragm. If both were used for Qi disorders, could the chest and diaphragm withstand such heavy medications? Zou claimed that Huoxiao tending toward Yang and Shuixiao tending toward Yin explains why Zang diseases transfer to Fu organs and Fu diseases transfer to the limbs/body. This requires clarification. The *Bencao Jing* mentions accumulated heat in the Five Zang organs; do they all enter the Stomach to cause distension and closure? Diseases are myriad; are they all located in the limbs/body? If Huoxiao tends toward Yang to resolve intense heat from Yin to Yang, tending toward Yang means entering Yang. Why enter Yin first? How can this not be its direction? If Shuixiao tends toward Yin to expel solid accumulations in Yang, what is expelled is in Yang, so its direction must also be Yang. To act otherwise implies ulterior motives. Humans may have such thoughts, but objects certainly do not. Such approximate discussions seek no truth and merely dazzle the eyes. Zou made another error, stating that adding Mangxiao to Jijiang Lihuang Wan to treat thirst removes stubborn masses, thereby promoting fluid circulation. Adding Mangxiao to Chaihu Jia Mangxiao Tang to stop dysentery removes accumulations, thereby stopping diarrhea. Alas, this shows a lack of deep thought. The syndrome of Jijiang Lihuang Wan is originally not a fixed mass; Dahuang would never be used in such small amounts (see Dahuang commentary); Mangxiao would not be added later. Moreover, the post-prescription note says: "Take one pill before meals, three times a day, gradually increase. If saliva appears in the mouth, add half liang of Mangxiao if thirsty." Without Mangxiao, fluids can still be generated. Is the fluid generation with Mangxiao different from that without it? Xu and You stated that thirst indicates Stomach heat, hence Mangxiao is added. Zou was too rigidly attached to the *Bencao Jing*. Chaihu Jia Mangxiao Tang states: "Tidal fever indicates excess." Heat-excess syndromes require purgation. Using Chaihu Jia Mangxiao Tang treats this heat-excess. It also says: "Add Mangxiao, boil until barely simmering, divide into two warm doses. If unresolved, prepare again." Was Mangxiao added not for purgation!? Why does Zou's view contradict this? He likely misunderstood the phrase "now there is loose stool." Zhongjing explicitly stated "slight loose stool" and "purgation is not the correct treatment." If tidal fever persists after purgation, how can one not follow up with appropriate purgatives? This is why careful examination is essential when reading ancient texts.