Arsenic trioxide

Arsenic trioxide, sold under the brand name Trisenox among others, is an inorganic compound and medication.[3] As an industrial chemical, its major uses include the manufacture of wood preservatives, pesticides, and glass.[4] As a medication, it is used to treat a type of cancer known as acute promyelocytic leukemia.[3] For this use it is given by injection into a vein.[3]

Arsenic trioxide
Arsenic trioxide   As   O
Clinical data
PronunciationAR se nik tri OKS id
Trade namesTrisenox, others
Other namesArsenic(III) oxide,
Arsenic sesquioxide,
Arseneous oxide,
Arseneous anhydride,
White arsenic,
Aqua Tofani[1]
License data
  • AU: X (High risk)
Routes of
Drug classAntineoplastic agent
ATC code
Legal status
Legal status
  • AU: S4 (Prescription only)
  • US: ℞-only
  • EU: Rx-only
Pharmacokinetic data
Protein binding75%
  • Diarsenic trioxide
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.014.075
Chemical and physical data
Molar mass197.840 g·mol−1
3D model (JSmol)
Density3.74 g/cm3
Melting point312.2 °C (594.0 °F)
Boiling point465 °C (869 °F)
Solubility in water20 g/L (25 °C)
(see text)
  • O1[As]3O[As]2O[As](O3)O[As]1O2
  • InChI=1S/As2O3/c3-1-4-2(3)5-1
Arsenic trioxide
ECHA InfoCard 100.014.075
EC Number
  • 215-481-4
GHS labelling:[2]
H300, H314, H350, H410
P201, P202, P260, P264, P270, P273, P280, P301+P330+P331, P303+P361+P353, P304+P340+P310, P305+P351+P338+P310, P308+P313, P363, P391, P405, P501
Safety data sheet (SDS) american elements SDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Common side effects include vomiting, diarrhea, swelling, shortness of breath, and headaches.[3] Severe side effects may include APL differentiation syndrome and heart problems.[3] Use during pregnancy or breastfeeding may harm the baby.[5][6] Arsenic trioxide has the formula As
.[7] Its mechanism in treating cancer is not entirely clear.[3]

Arsenic trioxide was approved for medical use in the United States in 2000.[3] It is on the World Health Organization's List of Essential Medicines.[8] Approximately 50,000 tonnes are produced a year.[9] Due to its toxicity, a number of countries have regulations around its manufacture and sale.[10]



Arsenic trioxide is used to treat a type of cancer known as acute promyelocytic leukemia (APL).[3] It may be used both in cases that are unresponsive to other agents, such as all-trans retinoic acid (ATRA) or as part of the initial treatment of newly diagnosed cases.[3] This initial treatment may include combination therapy of arsenic trioxide with all-trans retinoic acid (ATRA).[11]

Effectiveness appears similar to Realgar/Indigo naturalis, which can be taken by mouth and is less expensive but is less available.[12] It works by encouraging the proteosome breakdown of retinoic acid receptor alpha, by moving the protein on to the nuclear matrix and increasing ubiquitination.[13]

In the 1970s, Chinese researcher Zhang Tingdong and colleagues discovered this use.[14] It was approved for leukemia treatment in the United States in 2000.[15] University of Hong Kong developed a liquid form of arsenic trioxide that can be given by mouth.[16] Organoarsenic compounds, such as feed additives (roxarsone) and medication (neosalvarsan), are derived from arsenic trioxide.


Industrial uses include usage as a precursor to forestry products, in colorless glass production, and in electronics.[9] Being the main compound of arsenic, the trioxide is the precursor to elemental arsenic, arsenic alloys, and arsenide semiconductors. Bulk arsenic-based compounds sodium arsenite and sodium cacodylate are derived from the trioxide.

A variety of applications exploit arsenic's toxicity, including the use of the oxide as a wood preservative. Copper arsenates, which are derived from arsenic trioxide, are used on a large scale as a wood preservative in the U.S. and Malaysia, but such materials are banned in many parts of the world. This practice remains controversial.[9] In combination with copper(II) acetate, arsenic trioxide gives the vibrant pigment known as Paris green used in paints and as a rodenticide. This application has been discontinued.

Alternative medicine

Despite the well known toxicity of arsenic, arsenic trioxide was used in traditional Chinese medicine, where it is known as pi-shuang (Chinese: 砒霜; pinyin: pīshuāng; lit. 'arsenic frost'). In homeopathy, it is called arsenicum album. Some discredited patent medicines, e.g., Fowler's solution, contained derivatives of arsenic oxide.[17]


Arsenic trioxide is readily absorbed by the digestive system. Ingestion of as little as 0.1 grams can be fatal.[9]

Chronic arsenic poisoning is known as arsenicosis. This disorder affects workers in smelters, in populations whose drinking water contains high levels of arsenic (0.3–0.4 ppm), and in patients treated for long periods with arsenic-based pharmaceuticals. Similarly, studies on workers exposed in copper foundries in the U.S., Japan and Sweden indicate a risk of lung cancer 6–10 times higher for the most exposed workers compared with the general population. Long-term ingestion of arsenic trioxide either in drinking water or as a medical treatment can lead to skin cancer. Reproductive problems (high incidences of miscarriage, low birth weight, congenital deformations) have also been indicated in one study of women exposed to arsenic trioxide dust as employees or neighbours of a copper foundry.

In the U.S., the OSHA 1910.1018 occupational permissible exposure limit for inorganic arsenic compounds in breathing zone air is 0.010 mg/m3.

Production and occurrence

Historic arsenic mine Sankt Blasen, Austria

Arsenic trioxide can be generated via routine processing of arsenic compounds including the oxidation (combustion) of arsenic and arsenic-containing minerals in air. Illustrative is the roasting of orpiment, a typical arsenic sulfide ore.

2 As
+ 9 O
→ 2 As
+ 6 SO

Most arsenic oxide is, however, obtained as a volatile by-product of the processing of other ores. For example, arsenopyrite, a common impurity in gold- and copper-containing ores, liberates arsenic trioxide upon heating in air. The processing of such minerals has led to numerous cases of poisonings,[18] and after the mine is closed, the leftover trioxide waste will present environmental hazard (as was the case with the Giant Mine, for example). Only in China are arsenic ores intentionally mined.[9]

In the laboratory, it is prepared by hydrolysis of arsenic trichloride:[19]

2 AsCl3 + 3 H2O → As2O3 + 6 HCl

occurs naturally as two minerals, arsenolite (cubic) and claudetite (monoclinic). Both are relatively rare secondary minerals found in oxidation zones of As-rich ore deposits. Sheets of As2O3 stand for part of structures of the recently discovered minerals lucabindiite, (K,NH4)As4O6(Cl,Br),[20] and its sodium-analogue torrecillasite.[21]

Properties and reactions

Arsenic trioxide is an amphoteric oxide, and its aqueous solutions are weakly acidic. Thus, it dissolves readily in alkaline solutions to give arsenites. It is less soluble in acids, although it will dissolve in hydrochloric acid.[22]

With anhydrous HF and HCl, it gives AsF3 and the trichloride:[19]

As2O3 + 6 HX → 2 AsX3 + 3 H2O (X = F, Cl)

Only with strong oxidizing agents such as ozone, hydrogen peroxide, and nitric acid does it yield arsenic pentoxide, As
or its corresponding acid:[19]

2 HNO3 + As2O3 + 2 H2O → 2 H3AsO4 + N2O3

In terms of its resistance to oxidation, arsenic trioxide differs from phosphorus trioxide, which readily combusts to phosphorus pentoxide.

Reduction gives elemental arsenic or arsine (AsH
) depending on conditions:[19]

As2O3 + 6 Zn + 12 HNO3 → 2 AsH3 + 6 Zn(NO3)2 + 3 H2O

This reaction is used in the Marsh test.


In the liquid and gas phase below 800 °C, arsenic trioxide has the formula As
and is isostructural with P
. Above 800 °C As
significantly dissociates into molecular As
, which adopts the same structure as N
. Three forms (polymorphs) are known in the solid state: a high temperature ( > 110 °C) cubic As
, containing molecular As
, and two related polymeric forms.[23] The polymers, which both crystallize as monoclinic crystals, feature sheets of pyramidal AsO
units that share O atoms.[24]

claudetite I
claudetite II

Society and culture

Environmental effects

Smelting and related ore processing often generate arsenic trioxide, which poses a risk to the environment. For example, the Giant Mine in Canada processed substantial amounts of arsenopyrite-contaminated gold ores.

Arsenic poisoning in literature and society

The poisonous properties of arsenic are the subject of an extensive literature.[25][26][27]

In Austria, there lived the so-called "arsenic eaters of Styria", who ingested doses far beyond the lethal dose of arsenic trioxide without any apparent harm. Arsenic is thought to enable strenuous work at high altitudes, e.g. in the Alps.[28][29][30][31]


  1. Shakhashiri, B. Z. "Chemical of the Week: Arsenic". University of Wisconsin-Madison Chemistry Dept. Archived from the original on 2008-08-02. Retrieved 2008-08-03.
  2. "Safety Data Sheet". American Elements. 2021. Retrieved 4 January 2022.
  3. "Arsenic Trioxide Monograph for Professionals". Retrieved 15 November 2019.
  4. Landner, Lars (2012). Chemicals in the Aquatic Environment: Advanced Hazard Assessment. Springer Science & Business Media. p. 259. ISBN 9783642613340.
  5. British national formulary : BNF 76 (76 ed.). Pharmaceutical Press. 2018. p. 907. ISBN 9780857113382.
  6. "Arsenic trioxide (Trisenox) Use During Pregnancy". Retrieved 16 November 2019.
  7. Sun, Hongzhe (2010). Biological Chemistry of Arsenic, Antimony and Bismuth. John Wiley & Sons. p. 295. ISBN 9780470976227.
  8. World Health Organization (2019). World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
  9. Grund, S. C.; Hanusch, K.; Wolf, H. U. "Arsenic and Arsenic Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_113.pub2.
  10. Consolidated List of Products Whose Consumption And/or Sale Have Been Banned, Withdrawn, Severely Restricted Or Not Approved by Governments: Chemicals. United Nations Publications. 2009. p. 24. ISBN 9789211302196.
  11. Zhu, J.; Chen, Z.; Lallemand-Breitenbach, V.; De Thé, H. (2002). "How acute promyelocytic leukaemia revived arsenic". Nature Reviews Cancer. 2 (9): 705–714. doi:10.1038/nrc887. PMID 12209159. S2CID 2815389.
  12. Howard, Scott C. "Proposal for the inclusion of arsenic therapies in the WHO Model list of ESSENTIAL MEDICINES for the treatment of acute promyelocytic leukemia" (PDF). WHO. Archived from the original (PDF) on 2022-03-09. Retrieved 15 November 2019.
  13. Zhu, J; Koken, MH; Quignon, F; Chelbi-Alix, MK; Degos, L; Wang, ZY; Chen, Z; de Thé, H (15 April 1997). "Arsenic-induced PML targeting onto nuclear bodies: implications for the treatment of acute promyelocytic leukemia". Proceedings of the National Academy of Sciences of the United States of America. 94 (8): 3978–83. doi:10.1073/pnas.94.8.3978. PMID 9108090.
  14. Rao Y, Li R, Zhang D (June 2013). "A drug from poison: how the therapeutic effect of arsenic trioxide on acute promyelocytic leukemia was discovered". Sci China Life Sci. 56 (6): 495–502. doi:10.1007/s11427-013-4487-z. PMID 23645104.
  15. Bian Z, Chen S, Cheng C, Wang J, Xiao H, Qin H (2012). "Developing new drugs from annals of Chinese medicine". Acta Pharmaceutica Sinica B. 2: 1–7. doi:10.1016/j.apsb.2011.12.007.
  16. Au, W.-Y.; Kumana, C. R.; Kou, M.; Mak, R.; Chan, G. C.; Lam, C.-W.; Kwong, Y.-L. (2003). "Oral arsenic trioxide in the treatment of relapsed acute promyelocytic leukemia". Blood. 102 (1): 407–408. doi:10.1182/blood-2003-01-0298. PMID 12814916.
  17. Gibaud, S.; Jaouen, G. (2010). Arsenic-Based Drugs: From Fowler's Solution to Modern Anticancer Chemotherapy. Topics in Organometallic Chemistry. Vol. 32. pp. 1–20. doi:10.1007/978-3-642-13185-1_1. ISBN 978-3-642-13184-4.
  18. "Giant Mine – Northwest Territories Region – Indian and Northern Affairs Canada". Archived from the original on 2006-06-27. Retrieved 2007-08-28.
  19. Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY.
  20. Garavelli et al. 2013,
  21. Kampf et al. 2013,
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  26. Emsley, J. (2006). "Arsenic". The Elements of Murder: A History of Poison. Oxford University Press. pp. 93–197. ISBN 978-0-19-280600-0.
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  28. "Arsenic Eaters". New York Times. July 26, 1885.
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