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Some arsenite salts can be prepared from an aqueous solution of As 2 O 3. Examples of these are the meta-arsenite salts and at low temperature, hydrogen arsenite salts can be prepared, such as Na 2 H 2 As 4 O 8, NaAsO 2 ·4H 2 O, Na 2 HAsO 3 ·5H 2 O and Na 5 (HAsO 3)(AsO 3)·12H 2 O. [5]
Sodium arsenite can be inhaled or absorbed through the skin. Along with its known carcinogenic and teratogenic effects, contact with the substance can yield symptoms such as skin irritation, burns, itching, thickened skin, rash, loss of pigment, poor appetite, a metallic or garlic taste, stomach pain, nausea, vomiting, diarrhea, convulsions, decreased blood pressure, and headache.
The pigment was originally prepared by making a solution of sodium carbonate at a temperature of around 90 °C (194 °F), then slowly adding arsenious oxide, while constantly stirring until everything had dissolved. This produced a sodium arsenite solution.
In its standard state arsine is a colorless, denser-than-air gas that is slightly soluble in water (2% at 20 °C) [1] and in many organic solvents as well. [citation needed] Arsine itself is odorless, [5] but it oxidizes in air and this creates a slight garlic or fish-like scent when the compound is present above 0.5 ppm. [6]
[20] [21] Starting in the early 19th century and continuing into the 20th century, Fowler's solution, a toxic concoction of sodium arsenite, was sold. The organoarsenic compound Salvarsan was the first synthetic chemotherapeutic agent, discovered by Paul Ehrlich. [21]
Arsenate (+5 oxidation state) is the dominant form of arsenic in surface water, while arsenite (+3 oxidation state) is the dominant form in hypoxic to anoxic environments. Arsenite is more soluble and mobile than arsenate. Many species of bacteria can transform arsenite to arsenate in anoxic conditions by using arsenite as an electron donor. [189]
The determination of arsenic(V) compounds is the reverse of the standardization of iodine solution with sodium arsenite, where a known and excess amount of iodide is added to the sample: As 2 O 5 + 4 H + + 4 I − ⇌ As 2 O 3 + 2 I 2 + 2 H 2 O
Sodium dihydrogen arsenate is a colorless solid that is highly toxic. The salt is the conjugate base of arsenic acid: H 3 AsO 4 ⇌ H 2 AsO − 4 + H + (K 1 = 10 −2.19) In the laboratory, it is prepared in this way, crystallizing from a hot saturated aqueous solution, where it is highly soluble when hot (75.3 g in 100 mL at 100 °C).