Sodium methyl arsenate

Structural formula
General
Surname	Sodium methyl arsenate
other names	MSMA; Sodium methyl arsonate;
Molecular formula	CH 4 AsNaO 3
Brief description	colorless and odorless crystals
External identifiers / databases
EC number	218-495-9
ECHA InfoCard	100,016,815
PubChem	23664719
Wikidata	Q3066718
properties
Molar mass	161.95 g mol −1
Physical state	firmly
Melting point	130-140 ° C
Vapor pressure	0.0104 mPa
solubility	practically insoluble in water; slightly soluble in methanol (160 g l −1 at 25 ° C);
safety instructions
H and P phrases	H: 301-331-410
	P: 261-273-301 + 310-311-501
Toxicological data	700 mg kg −1 ( LD 50 , rat , oral )
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Sodium methyl arsenate is a universal plant protection product , which is mainly used as a herbicide. Its use was banned early on in Germany, but it is still used in the USA. It is a potent class 1 carcinogen .

Manufacturing

Sodium methyl arsenate can be obtained from chloromethane , arsenic (III) oxide , sulfuric acid and caustic soda :

${\ displaystyle \ mathrm {CH_ {3} Cl + As_ {2} O_ {3} + H_ {2} SO_ {4} + NaOH \ longrightarrow CH_ {4} AsNaO_ {3}}}$

It can also be produced by methylating sodium arsenite with dimethyl sulfate :

${\ displaystyle \ mathrm {NaAsO_ {2} + C_ {2} H_ {6} O_ {4} S \ longrightarrow CH_ {4} AsNaO_ {3}}}$

use

Sodium methyl arsenate is used as a defoliant in cotton crops, particularly in Texas and Louisiana, and as a herbicide on golf courses.

Admission

Sodium methyl arsenate is not approved as a crop protection agent in the European Union or Switzerland .

Individual evidence

↑ ^a ^b ^c Entry on sodium methyl arsonate in the GESTIS substance database of the IFA , accessed on March 25, 2013 (JavaScript required)
↑ ^a ^b ^c ^d Robert Krieger (Ed.): Hayes' Handbook of Pesticide Toxicology, Volume 1 . Elsevier, 1999, ISBN 978-0-12-374367-1 , pp. 779 ( limited preview in Google Book search).
↑ ^a ^b Data sheet Monosodium acid methane arsonate sesquihydrate, analytical standard at Sigma-Aldrich , accessed on March 25, 2013 ( PDF ).
↑ ^a ^b Entry on SODIUM METHANEARSONATE in the Hazardous Substances Data Bank , accessed on August 4, 2018.
↑ MS Cox, PF Bell and JL Kovar, Arsenic supply characteristics of four cotton-producing soils; Plant and Soil Volume 180, Number 1, 11-17, 1996, doi: 10.1007 / BF00015406 .
^ Directorate-General for Health and Food Safety of the European Commission: EU pesticide database ; Entry in the national directory of plant protection products in Switzerland ; Retrieved June 25, 2016.

[gestis-1] Entry on sodium methyl arsonate in the GESTIS substance database of the IFA , accessed on March 25, 2013 (JavaScript required)

[hayes-2] Robert Krieger (Ed.): Hayes' Handbook of Pesticide Toxicology, Volume 1 . Elsevier, 1999, ISBN 978-0-12-374367-1 , pp. 779 ( limited preview in Google Book search).

[Sigma-3] Data sheet Monosodium acid methane arsonate sesquihydrate, analytical standard at Sigma-Aldrich , accessed on March 25, 2013 ( PDF ).

[pc-4] Entry on SODIUM METHANEARSONATE in the Hazardous Substances Data Bank , accessed on August 4, 2018.

[5] MS Cox, PF Bell and JL Kovar, Arsenic supply characteristics of four cotton-producing soils; Plant and Soil Volume 180, Number 1, 11-17, 1996, doi: 10.1007 / BF00015406 .

[6] Directorate-General for Health and Food Safety of the European Commission: EU pesticide database ; Entry in the national directory of plant protection products in Switzerland ; Retrieved June 25, 2016.