Molecular Formula: C₆H8AsNO₃
Molar mass: 217.05 g/mol
EINECS: 202-674-3
Flash Point: 273.4 °C
Boiling Point: 528.5 °C at 760 mmHg
Vapour Pressure: 5.34E-12 mmHg at 25°C
Melting point: ≥300 °C(lit.)
Water solubility: Slightly soluble
Appearance: Off-white fine crystalline powder
Product categories: As (Arsenic) Compounds;Semimetal Compounds;Classes of Metal Compounds
Structure of Arsanilic acid (98-50-0):

H-Bond Donor: 3
H-Bond Acceptor: 4
IUPAC Name: (4-Aminophenyl)arsonic acid
Canonical SMILES: C1=CC(=CC=C1N)[As](=O)(O)O
InChI: InChI=1S/C6H8AsNO3/c8-6-3-1-5(2-4-6)7(9,10)11/h1-4H,8H2,(H2,9,10,11) 
InChIKey: XKNKHVGWJDPIRJ-UHFFFAOYSA-N

 Arsanilic acid (98-50-0) was initially used in medicine to treat simple skin diseases. In 1905, H.W. Thomas and A. Breinl, reported that atoxyl was active against the trypanosomes of sleeping sickness. The effect was however not very pronounced and the necessary dosage was so high that toxic side effects far outweighed the benefits. Nevertheless, the discovery of arsanilic acid's activity against trypanosomes was the basis for a major advance by the bacteriologist Paul Ehrlich.The result of this collaboration was the discovery of the drug Salvarsan in 1909, which also was later abandoned but which accelerated the growth of medicinal chemistry.

 Arsanilic acid (98-50-0) was used as a drug in the late 19th and early 20th centuries but is now considered prohibitively toxic.

 Arsanilic acid (98-50-0) was first reported in 1859 by Antoine Béchamp.The original synthesis, which involved the reaction of aniline and arsenic acid, remains useful today.Béchamp optimistically chose the name Atoxyl, referring to its reduced toxicity compared to arsenic.

IARC Cancer Review: Animal Inadequate Evidence IMEMDT    IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man . 23 (1980),p. 39.(World Health Organization, Internation Agency for Research on Cancer,Lyon, France.: ) (Single copies can be ordered from WHO Publications Centre U.S.A., 49 Sheridan Avenue, Albany, NY 12210) . Reported in EPA TSCA Inventory. Arsenic and its compounds are on the Community Right-To-Know List.

Poison by intravenous and intraperitoneal routes. Moderately toxic by ingestion. Flammable, decomposes with heat to yield flammable vapors. When heated to decomposition or on contact with acid or acid fumes it emits highly toxic fumes of As and NO_x. See also ARSENIC COMPOUNDS and ANILINE.

Hazard Codes: T,N
Risk Statements:
23:  Toxic by inhalation
25:  Toxic if swallowed
50:  Very Toxic to aquatic organisms
53:  May cause long-term adverse effects in the aquatic environment
Safety Statements:
20:  When using, do not eat or drink
21:  When using, do not smoke
28:  After contact with skin, wash immediately with plenty of ... (to be specified by the manufacturer)
28A     After contact with skin, wash immediately with plenty of water.
45:  In case of accident or if you feel unwell, seek medical advice immediately (show label where possible)
60:  This material and/or its container must be disposed of as hazardous waste
61:  Avoid release to the environment. Refer to special instructions safety data sheet

OSHA PEL: TWA 0.5 mg(As)/m³
ACGIH TLV: BEI: 35 μ (As)/L inorganic arsenic and methylated metabolites in urine

For occupational chemical analysis use NIOSH: Arsenic, Organo-, 5022.

 Arsanilic acid (98-50-0)is the organoarsenic compound also called p-aminophenylarsenic acid ; 4-Aminobenzenearsonic acid ; 4-Arsanilic acid, Atoxyl ; 4-Aminophenylarsonic acid.It is hazardous,so the first aid measures and others should be known.Such as: When on the skin: first,should  flush skin with plenty of water immediatelyfor at least 15 minutes while removing contaminated clothing. Secondly,Get shoesmedical aid . Or in the eyes: Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids.Then get medical aid soon.While ,it's Inhaled: Remove from exposure and move to fresh air immediately.Give artificial respiration while not breathing. When breathing is difficult, give oxygen. And as soon as to get medical aid. Then you have the ingesting of the product : Wash mouth out with water,and get medical aid immediately.
In addition, it is not compatible with strong oxidizing agents, and you must not take it with incompatible materials.And also prevent it to broken down into hazardous decomposition products: carbon monoxide, carbon dioxide, oxides of arsenic, oxides of nitrogen.