Sodium arsenate is the
inorganic compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...
with the
formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...
Na
3AsO
4. Related salts are also called sodium arsenate, including Na
2HAsO
4 (
disodium hydrogen arsenate
Disodium hydrogen arsenate is the inorganic compound with the formula Na2HAsO4.7H2O. The compound consists of a salt and seven molecules of water of crystallization although for simplicity the formula usually omits the water component. The other ...
) and NaH
2AsO
4 (
sodium dihydrogen arsenate). The trisodium salt is a white or colourless solid that is highly toxic. It is usually handled as the dodecahydrate Na
3AsO
4.12H
2O.
The compound can be obtained by neutralizing
arsenic acid
Arsenic acid or trihydrogen arsenate is the chemical compound with the formula . More descriptively written as , this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as ...
:
:H
3AsO
4 + 3 NaOH → Na
3AsO
4 + 3 H
2O
The salt (as its dodecahydrate) is isomorphous with
trisodium phosphate
Trisodium phosphate (TSP) is the inorganic compound with the chemical formula . It is a white, granular or crystalline solid, highly soluble in water, producing an alkaline solution. TSP is used as a cleaning agent, builder, lubricant, food a ...
.
[Remy, Francis; Guerin, Henri "Radiocrystallographic study of dodecahydrate trisodium arsenate and vanadate Na3AsO4.12H2O and Na3VO4.12H2O, and some hydrates of fluorinated or hydroxylated salts of general formula: M3XO4.xMY.(10 - x)H2O where M = Na, K; X = P, As, V and Y = F, OH" Bulletin de la Société Chimique de France 1970, vol. 6, pp. 2073-8.] The anion AsO
43- exists at high pH, but below pH 11.5, it converts to HAsO
42- (also written HOAsO
32-).
References
Arsenates
Sodium compounds
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