Sal ammoniac, Salmiac, Nushadir salt, Sal armagnac, Salt armoniack
3D model (JSmol)
|Molar mass||53.49 g·mol−1|
|Appearance||White solid, hygroscopic|
|Melting point||338 °C (640 °F; 611 K) decomposes, sublimes|
|Boiling point||520 °C (968 °F; 793 K)|
|Sublimes at 337.6 °C
|244 g/L (−15 °C)
294 g/L (0 °C)
383.0 g/L (25 °C)
454.4 g/L (40 °C)
740.8 g/L (100 °C)
Solubility product (Ksp)
|30.9 (395 g/L)|
|Solubility||Soluble in liquid ammonia, hydrazine,
Slightly soluble in acetone
Insoluble in diethyl ether, ethyl acetate
|Solubility in methanol||3.2 g/100 g (17 °C)
3.35 g/100 g (19 °C)
3.54 g/100 g (25 °C)
|Solubility in ethanol||6 g/L (19 °C)|
|Solubility in glycerol||97 g/kg|
|Solubility in sulfur dioxide||0.09 g/kg (0 °C)
0.031 g/kg (25 °C)
|Solubility in acetic acid||0.67 g/kg (16.6 °C)|
|Vapor pressure||133.3 Pa (160.4 °C)
6.5 kPa (250 °C)
33.5 kPa (300 °C)
Refractive index (nD)
|1.642 (20 °C)|
Std enthalpy of
Gibbs free energy (ΔfG˚)
|B05XA04 (WHO) G04BA01 (WHO)|
|Safety data sheet||ICSC 1051|
|GHS signal word||Warning|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|1650 mg/kg (rats, oral)|
|US health exposure limits (NIOSH):|
|TWA 10 mg/m3 ST 20 mg/m3 (as fume)|
IDLH (Immediate danger)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Ammonium chloride is an inorganic compound with the formula NH4Cl and a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of the natural, mineralogical form of ammonium chloride. The mineral is commonly formed on burning coal dumps from condensation of coal-derived gases. It is also found around some types of volcanic vents. It is mainly used as fertilizer and a flavouring agent in some types of liquorice. It is the product from the reaction of hydrochloric acid and ammonia.
- CO2 + 2 NH3 + 2 NaCl + H2O → 2 NH4Cl + Na2CO3
In addition to being the principal method for the manufacture of ammonium chloride, that method is used to minimize ammonia release in some industrial operations.
- NH3 + HCl → NH4Cl
Ammonium chloride occurs naturally in volcanic regions, forming on volcanic rocks near fume-releasing vents (fumaroles). The crystals deposit directly from the gaseous state and tend to be short-lived, as they dissolve easily in water.
- NH4Cl → NH3 + HCl
Ammonium chloride reacts with a strong base, like sodium hydroxide, to release ammonia gas:
- NH4Cl + NaOH → NH3 + NaCl + H2O
Similarly, ammonium chloride also reacts with alkali metal carbonates at elevated temperatures, giving ammonia and alkali metal chloride:
- 2 NH4Cl + Na2CO3 → 2 NaCl + CO2 + H2O + 2 NH3
Some of ammonium chloride's reactions with other chemicals are endothermic like its reaction with barium hydroxide and its dissolving in water.
The main application of ammonium chloride is as a nitrogen source in fertilizers (corresponding to 90% of the world production of ammonium chloride) such as chloroammonium phosphate. The main crops fertilized this way are rice and wheat in Asia.
Ammonium chloride was used in pyrotechnics in the 18th century but was superseded by safer and less hygroscopic chemicals. Its purpose was to provide a chlorine donor to enhance the green and blue colours from copper ions in the flame.
It had a secondary use to provide white smoke, but its ready double decomposition reaction with potassium chlorate producing the highly unstable ammonium chlorate made its use very suspect.
Ammonium chloride is used as a flux in preparing metals to be tin coated, galvanized or soldered. It works as a flux by cleaning the surface of workpieces by reacting with the metal oxides at the surface to form a volatile metal chloride. For that purpose, it is sold in blocks at hardware stores for use in cleaning the tip of a soldering iron, and it can also be included in solder as flux.
Ammonium chloride is used as an expectorant in cough medicine. Its expectorant action is caused by irritative action on the bronchial mucosa, which causes the production of excess respiratory tract fluid, which presumably is easier to cough up. Ammonium salts are an irritant to the gastric mucosa and may induce nausea and vomiting.
Ammonium chloride is used as a systemic acidifying agent in treatment of severe metabolic alkalosis, in oral acid loading test to diagnose distal renal tubular acidosis, to maintain the urine at an acid pH in the treatment of some urinary-tract disorders.
Ammonium chloride, under the name sal ammoniac or salmiak is used as food additive under the E number E510, working as a yeast nutrient in breadmaking and as an acidifier. It is a feed supplement for cattle and an ingredient in nutritive media for yeasts and many microorganisms.
Ammonium chloride is used to spice up dark sweets called salmiak (popular in Nordic and other nearby countries), in baking to give cookies a very crisp texture, and in the liquor Salmiakki Koskenkorva for flavouring. In Iran, Tajikistan, India, Pakistan and Arab countries it is called "Noshader" and is used to improve the crispness of snacks such as samosas and jalebi.
In the laboratory
Ammonium chloride is used to produce low temperatures in cooling baths. Ammonium chloride solutions with ammonia are used as buffer solutions including ACK (Ammonium-Chloride-Potassium) lysis buffer.
In paleontology, ammonium chloride vapor is deposited on fossils, where the substance forms a brilliant white, easily removed and fairly harmless and inert layer of tiny crystals. That covers up any coloration the fossil may have, and if lighted at an angle highly enhances contrast in photographic documentation of three-dimensional specimens. The same technique is applied in archaeology to eliminate reflection on glass and similar specimens for photography.
Giant squid and some other large squid species maintain neutral buoyancy in seawater through an ammonium chloride solution which is found throughout their bodies and is less dense than seawater. This differs from the method of flotation used by most fish, which involves a gas-filled swim bladder. The solution tastes somewhat like salmiakki and makes giant squid unattractive for general human consumption.
Ammonium chloride is used in a ~5% aqueous solution to work on oil wells with clay swelling problems. It is also used as electrolyte in zinc–carbon batteries. Other uses include in hair shampoo, in the glue that bonds plywood, and in cleaning products. In hair shampoo, it is used as a thickening agent in ammonium-based surfactant systems such as ammonium lauryl sulfate. Ammonium chloride is used in the textile and leather industry, in dyeing, tanning, textile printing and cotton clustering. Around the turn of the 20th Century, Ammonium Chloride was used in aqueous solution as the electrolyte in Leclanché cells. These cells found a commercial use as the "local battery" in subscribers' telephone installations. In woodworking, a solution of ammonium chloride and water, when applied to unfinished wood, will burn when subjected to a heat gun resulting in a branding iron mark without use of a branding iron. The solution can be painted onto the wood or applied with a common rubber stamp.
The earliest mention of ammonium chloride was in 554 A.D. in China. At that time, ammonium chloride came from two sources: (1) the vents of underground coal fires in Central Asia, specifically, in the Tian Shan mountains (which extend from Xinjiang province of northwestern China through Kyrgyzstan) as well as in the Alay (or Alai) mountains of southwestern Kyrgyzstan, and (2) the fumaroles of the volcano Mount Taftan in southeastern Iran. (Indeed, the word for ammonium chloride in several Asian languages derives from the Iranian phrase anosh adur (immortal fire), a reference to the underground fires.) Ammonium chloride was then transported along the Silk Road eastwards to China and westwards to the Muslim lands and Europe.
- Pradyot, Patnaik (2003). Handbook of Inorganic Chemicals. The McGraw-Hill Companies, Inc. ISBN 0-07-049439-8.
- Wiberg, Egon; Wiberg, Nils (2001). Inorganic Chemistry (illustrated ed.). Academic Press. p. 614. ISBN 0-12-352651-5.
- Seidell, Atherton; Linke, William F. (1919). Solubilities of Inorganic and Organic Compounds (2nd ed.). D. Van Nostrand Company.
Results here are multiplied by water's density at temperature of solution for unit conversion.
- "Solubility Products of Selected Compounds". Salt Lake Metals. Retrieved 2014-06-11.
- Sigma-Aldrich Co., Ammonium chloride. Retrieved on 2014-06-11.
- "NIOSH Pocket Guide to Chemical Hazards #0029". National Institute for Occupational Safety and Health (NIOSH).
- Rowley, Steven P. (2011). General Chemistry I Laboratory Manual (Second ed.). Kendall Hunt. ISBN 978-0-7575-8942-3.
- Dr. K. G. Bothara (7 October 2008). Inorganic Pharmaceutical Chemistry. Pragati Books Pvt. Ltd. pp. 13–. ISBN 978-81-85790-05-3. Retrieved 12 October 2011.
- Karl-Heinz Zapp "Ammonium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2012, Wiley-VCH, Weinheim. doi:10.1002/14356007.a02_243
- John A. Conkling; Christopher J. Mocella (2010). Chemistry of Pyrotechnics (2nd ed.). CRC Press. ISBN 978-1574447408.
- Tenney L Davis (2012). Chemistry of Powder and Explosives. Angriff Press. ISBN 978-0945001171.
- K. L. Kosanke; B. J. Kosanke; Barry T. Sturman; Robert M. Winokur (2012). Encyclopedic Dictionary of Pyrotechnics (and Related Subjects). Journal of Pyrotechnics. ISBN 978-1889526195.
- Smith, Jim; Hong-Shum, Lily (2011). Food Additives Data Book (2nd ed.). John Wiley & Sons. p. 540. ISBN 1444397737.
- Christine S. (8 August 2011). "In Salmiak Territory". The Harvard Crimson. Retrieved 8 August 2017.
- "A New Frigorifick Experiment Shewing, How a Considerable Degree of Cold May be Suddenly Produced without the Help of Snow, Ice, Haile, Wind, or Niter, and That at Any Time of the Year". Philosophical Transactions. 1: 255–261. 18 July 1666.
- That ammonium chloride was imported into China from Sogdiana in Central Asia is mentioned in the Wei shu (History of the Wei [peoples of what is now China]), which was compiled by Wei Shou 魏收 (506–572 A.D.). (Sutton et al., 2008), p. 596. However, it may have been imported into China even before 150 A.D.: there is a brief mention of what might have been ammonium chloride in the Chinese Chou I Tshan Thung Chhi Chu 周易参同契註 [The Kinship of the Three and the Book of Changes, with Commentary] (142 A.D.) by Wei Boyang. (Needham et al., 1980), p. 439.
- The locations of the sources of ammonium chloride in the burning coal deposits of Central Asia are shown on the following map:
- (Sutton et al., 2008), pp. 595-596, especially Fig. 6 (map).
- Jameson, Robert, Manual of Mineralogy … (Edinburgh, Scotland: Archibald Constable & Co. and Hurst, Robinson & Co., 1821), p. 12. From p. 12: "Volcanic Sal Ammoniac. … Geographic Situation.—It occurs in the vicinity of burning beds of coal, both in Scotland and England; and in many volcanic districts in different parts of the world."
- Nicol, James, Manual of Mineralogy; … (Edinburgh, Scotland: Adam and Charles Black and Longman, Brown, Green, and Longmans, 1849), p. 336. From p. 336: "It [i.e., ammonium chloride] is sometimes found near ignited coal seams, as at St Etienne in France, near Newcastle, and in Scotland."
- (Bischof, 1854), pp. 213–214: "Chloride of ammonium is also found at other places, as a sublimate arising from the combustion of coal strata; for instance, at St. Etienne, near Lyons, at Newcastle and at Glan in Rhenish Bavaria."
- les Élèves mineurs de Saint-Étienne [the pupils of Saint-Étienne] (1822) "Note sur le Sel ammoniaque que produit une mine de houille incendiée" (Note on the ammonium salt that a burning coal mine produces), Annales de Chimie et de Physique, 21 : 158–159. [in French]
- The Arab geographer Yaqut al-Hamawi (1179–1229) or "Jakut" mentioned that ammonium chloride was harvested from "Damindan" (Tamindan), a valley on the volcano Mount Taftan in southwestern Iran. See: von Lippmann, E.O., "Wan and wofür erscheint zuerst die Bezeichnung Ammoniak?" (When and why did the term "ammonia" first appear?) In: Lippmann, Edmund O., ed., Abhandlungen und Vorträge zur Geschichte der Naturwissenschaften (Essays and Lectures on the History of the Sciences), vol. 2, (Leipzig, Germany: Veit & Co., 1913), pp. 230–237. From pp. 232–233: " … berichtet er, daß der Höhle Demindân in Persien ein Dampf entströme und sich beim Erkalten als Nuschadir niederschlage, den man von da aus in alle Welt versende." ( … he [i.e., Yaqut] reported that a vapor streams out of the caves at Damindan in Persia and upon cooling precipitates as nushadir [i.e., ammonium chloride], which is conveyed from there throughout the world.) In discussing ancient China's sources of ammonium chloride, Needham et al. state: "The most westerly region of all [of the regions that produce ammonium chloride] lies further to the south, in Persian Baluchistan, where the Damindān (now Tamindan) valley in the Kūh-i-Taftan range, a relatively inactive volcanic massif, produces sal ammoniac [i.e., ammonium chloride] down to this day." (Needham et al., 1980), p. 439.
- Ammonium chloride was later harvested from other volcanoes: The Arabs harvested it from Mount Etna in Sicily during the 10th century.
- The Arab geographer Al-Muqaddasi (c. 945/946 - 991) mentioned that ammonium chloride was obtained from Mt. Etna. See: Lippmann, Edmund Oskar von, Entstehung und Ausbreitung der Alchemie … (Origin and Spread of Alchemy … ), vol. 1, (Berlin, Germany: Springer, 1919), p. 404. From p. 404: " … er erwähnt, daß der dortige Salmiak nicht von gleicher Güte ist wie der Siciliens, dessen Lager jetzt aber schon erschöpft seien, … " ( … he mentions that the salmiak [i.e., ammonium chloride] there [i.e., in Fergana ] is not of equal value to that of Sicily’s, whose deposits are now, however, exhausted, … )
- The Arab geographer ibn Hawqal (d. ca. 978) also mentioned that ammonium chloride was obtained from fumaroles on the slopes of Mt. Etna. See: Ruska, Julius (1928) "Die Salmiak in die Geschichte der Alchemie" (Ammonium chloride in the history of alchemy), Zeitschrift für angewandte Chemie, 41 : 1321–1324.
- (Sutton et al., 2008), p. 595.
- Breislak, Scipion, Essais mineralogiques sur la solfatare de Pouzzole (Naples, Italy: Janvier Giaccio, 1792), p. 140. From p. 140: "Deux endroits de la Solfatare, celui où est construite la fontaine de vapeurs, et un autre à peu de distance produisent le muriate d'ammoniaque." (Two places on Solfatare — that where the fumerole has formed and another a little distance away — produce muriate of ammonia [i.e., ammonium chloride].)
- (Lémery, Nicolas) (1705) "Diverses observations chimiques. I." (Various chemical observations. I.), Histoire de l'Académie royale des sciences: année MDCCV, avec les memoires … , p. 66. From p. 66: "Monsieur Lémery a eu entre les mains un Sel tiré du Mont Vesuve, & que l'on appelle Sel Armoniac naturel." (Mr. Lémery got hold of a salt [which was] extracted from Mount Vesuvius, and which is called natural Armenian salt [i.e., ammonium chloride].)
- Bischof, Gustav with Benjamin H. Paul and J. Drummond, trans., Elements of Chemical and Physical Geology, vol. 1 (London, England: the Cavendish Society, 1854), p. 212.
- (Sutton et al., 2008), p. 599.
- Marcellin, Jean Baptiste Geneviève, Baron Bory de Saint-Vincent, Dictionnaire classique d'histoire naturelle, vol. 1 (Paris, France: Rey et Gravier, 1822), p. 270. From p. 270: "On trouve ce Minéral dans presque tous les volcans. … Elle se trouve également en Tartarie, dans le pays des Kalmuks; en Perse, au Thibet, dans l'île de Bourbon, en Bucharie, … " (One finds this mineral [i.e., ammonium chloride] in nearly every volcano … It is found also in Tartary [i.e., a region extending from Central Asia eastwards to the Pacific Ocean], in the country of the Kalmyks, in Persia, in Tibet, on Bourbon Island [i.e., Réunion], in Bucharia [i.e., a region of Central Asia extending from Turfan through Uzbekistan and Tajikistan ] … )
- Bunsen, Robert (1847) "Ueber den innern Zusammenhang der pseudovulkanischen Erscheinungen Islands" (On the intrinsic relationship of pseudo-volcanic phenomena of Iceland), Annalen der Chemie and Pharmacie, 62 : 1–59, see pp. 8–9. From pp. 8–9: "Im Juli 1846, also nur wenige Monate nach dem Ausbruch des Vulkans, wo ich in diesen Gegenden verweilte, zeigte sich der untere Theil dieses Stromes mit dampfenden Fumarolen übersäet, in denen sich eine solche Menge reiner, zum Theil sehr schön krystallisirter Salmiak sublimirte, dass man dort, trotz der unaufhörlichen Regengüsse, dieses wertvolle Salz zu Hunderten von Pfunden hätte sammeln können." (In July 1846, thus only months after the eruption of the volcano [i.e., Mt. Hekla], where I stayed in this region, the lower part of this [lava] flow appeared studded with steaming fumaroles, in which such a quantity of pure and sometimes very beautifully crystallized ammonium chloride had sublimated that one could have collected there — despite ceaseless downpours — hundreds of pounds of this valuable salt.)
- Del Campo, Ángel (1912) "Los sublimados blancos del volcán Chinyero (Canarias)" (The white sublimates of the volcano Chinyero in the Canary Islands), Anales de la Sociedad Española de Física y Química, 10 : 431–449.
- Shipley, J.W., (1919) "Scientific results of the Katmai expeditions of the National Geographic Society: VII. Ammonia and nitrous nitrogen in the rain water of southwestern Alaska," Ohio Journal of Science, 19 (4) : 230–234. Available at: Ohio State University
- (Sutton et al., 2008), p. 599.
- The term for "ammonium chloride" in Arabic is nūshādir or nūshādur, in Sanskit, navasadaru or navasara, in Chinese, nao sha, and similarly in Armenian and Syriac. (Sutton et al., 2008), p. 596.
- In De Lapidibus (About Stones), which is attributed to "Pseudo-Aristotle" and which dates from ca. 750–870 A.D., is a brief statement that ammonium chloride was created at the public baths (from the soot of the fires that served to heat the bath waters). Ruska, Julius, Das Steinbuch des Aristoteles mit literargeschichtlichen Untersuchungen nach der arabischen Handschrift der Bibliothèque Nationale [The book of stones of Aristotle with literary-historical investigations into the Arabic manuscript of the Bibliothèque Nationale] (Heidelberg, Germany: Carl Winter, 1912), p. 191. From p. 191 (in Latin): "Et unus lapis est qui vocatur nasciadhor i. liscianada qui fit in balneis." (And there is one stone that is called nasciadhor [i.e., nûshâdur, ammonium chloride] or liscianada that is made [i.e., created] in the baths.) See also: (Sutton et al., 2008), p. 595.
- The Persian geographer Al-Istakhri (d. 957 A.D.) stated that ammonium chloride was obtained from the soot of camel dung that was burned to heat the public baths in Alexandria. See: (Lippmann, 1919), p. 403. From p. 403: Istakhri " … bestätigt das persische Vorkommen … des Nûschâdirs, 'den die Ägypter aus dem Rauche ihrer Bäder haben' [aus dem Rauche des zum Heizen gebräuchlichen getrockneten Kamelmistes], … " (Istakhri confirms the occurrence in Persia … of ammonium chloride (nûshâdir), "which the Egyptians have [obtained] from the smoke of their baths" [i.e., from the smoke of the dried camel dung that's used for heating] … ) See also: (Sutton et al., 2008), p. 595.
The production of ammonium chloride from the soot of burned animal dung was reported early in the 18th century by a number of European observers:
- Sicard, Claude (S.J.), Nouveaux Mémoires de la Compagnie de Jesus dans le Levant [New memoirs of the Jesuits in the Levant], vol. 2 (Paris, France: Nicolas le Clerc, 1717), pp. 96–98. From pp. 96–98: " … nous arrivâmes sur le midy à Desmayer … " ( … we arrived at midday at Desmayer, a town [in the Nile delta] which is inhabited only by Muslims. It is in this place that the most esteemed sal armoniac [i.e., ammonium chloride] in all Egypt is made. This salt is made in ovens, whose top is vented lengthwise and in several places. One places in these vents twenty or thirty round glass bottles, about a foot and a half in diameter, with a neck of half a foot [across]. The bottles are sealed well: filled with soot and a little sea salt, and animal urine. Then one constructs a layer of loam and brick [on top of the oven], which covers everything except the tops of the bottles' necks, which [remain open] to the air. Then a fire is lit in the oven, and it is maintained continually for three days and three nights. The phlegm [i.e., liquid components] of the material contained in the bottles is driven off, and the acid salts and alkalies meet and cling to each other near the neck, [where they] form a white, round mass. The operation being completed, all of the bottles are broken, and these masses are removed, which are called "sal armoniac". It is to be noted that the soot of which I spoke, is produced by the smoke of pats, which is called gellée in Arabic. They [i.e., the pats] are formed from animal manure. Any other smoke is unlikely to condense into sal armoniac.)
- Geoffroy, Étienne (1720) "Observations sur la nature et la composition du sel ammoniac" (Observations on the nature and composition of ammonium chloride), Histoire de l'Academie Royale des Sciences: année MDCCXX, avec les memoires … , pp. 189–191.
- Lemere (1719) "Adressé à l'Académie sur le sel ammoniac, etc." (Address to the [French Royal] Academy [of Sciences] on ammonium chloride, etc.), Histoire de l'Academie Royale des Sciences: année MDCCXX, avec les memoires … , pp. 191–194.
- (Lemere) (1716) "Observations sur la nature et la composition du sel ammoniac," Histoire de l'Academie Royale des Sciences: année MDCCXX, avec les memoires … , pp. 195–207. On p. 202, Lemere states that ammonium chloride can be made by combining ammonium carbonate and hydrochloric acid: "L'on prend de l'esprit ou du sel volatil d'urine; on jette dessus de l'esprit de sel marin, jusqu'à ce qu'il ne se fasse plus de fermentation; on fait évaporer au sable la liqueur, qui, étant séche, fournit un sel salé qui a les mêmes effets que le sel ammoniac." (One takes the spirit or volatile salt of urine [i.e., ammonium carbonate]; one tosses on it spirit of sea salt [i.e., hydrochloric acid], until it no longer makes fermentation [i.e., effervesces]; one evaporates, on a sand [bath], the solution, which, [upon] being dry, furnishes a salty solid which has the same effects as ammonium chloride.)
- Duhamel du Monceau, Henri-Louis (1735) "Sur le sel ammoniac," Histoire de l'Academie Royale des Sciences: année MDCCXXXV, avec les memoires … , pp. 106–116 ; 414–434 ; 483–504.
- Ellis, John (1760) "The method of making sal ammoniac in Egypt; as communicated by Dr. Linnaeus from his pupil Dr. Hasselquist, who had been lately in those parts," Philosophical Transactions of the Royal Society of London, 51: 504–506.
- Beckmann, Johann, Beyträge zur Geschichte der Erfindungen [Contributions to the history of inventions] (Leipzig, Germany: Paul Gotthelf Kummer, 1805), vol. 5, 4. Salmiak, pp. 254–285. English translations: (1) Beckmann, Johann with William Johnston, trans., A History of Inventions and Discoveries, 2nd ed. (London, England: Walker, 1814), vol. 4, pp. 360–384. ; and (2) Beckmann, Johann with William Johnston, trans., A History of Inventions, Discoveries, and Origins, 4th ed. (London, England: Henry G. Bohn, 1846), vol. 2, pp. 396–407.
- Multhauf, Robert P. (1965) "Sal Ammoniac: a case history in industrialization," Technology and Culture, 6 (9) : 569–586.
- Sutton, Mark A.; Erisman, Jan Willem; Dentener, Frank; Möller, Detlev (2008) "Ammonia in the environment: From ancient times to the present," Environmental Pollution, 156 : 583–604. Available at: ResearchGate
- Bischof, Gustav with Benjamin H. Paul and J. Drummond, trans., Elements of Chemical and Physical Geology, vol. 1 (London, England: the Cavendish Society, 1854).
- Needham, Joseph; Ho Ping-Yü; Lu Gwei-Djen; Sivin, Nathan, Science and Civilization in China, vol. 5: Chemistry and Chemical Technology, Part IV: Spagyrical discovery and invention: apparatus, theories and gifts (Cambridge, England: Cambridge University Press, 1980).
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