Arsenic acid, also known as trihydrogen arsenate or arsoric acid, is a chemical compound with the formula H₃AsO₄. It is the arsenic analogue of phosphoric acid, and behaves very similarly to phosphate salts. Arsenic acid is a tetrahedral molecule with three hydroxyl groups attached to an arsenic atom. It is a strong acid that can ionize in three steps, releasing hydrogen ions and arsenate ions.

Arsenic acid is not found as a pure substance, but only in aqueous solutions, where it is largely ionized. It can be prepared by dissolving arsenic pentoxide in water or by oxidizing arsenious acid with a strong oxidizer such as hydrogen peroxide or nitric acid. Arsenic acid is a powerful oxidizing agent that can convert iodide to iodine, sulfide to sulfur, and ferrous to ferric ions. It can also react with metals to form arsenates, such as calcium arsenate or lead arsenate.

Arsenic acid is extremely toxic and carcinogenic, and can cause severe damage to the skin, eyes, respiratory system, and internal organs. It is also harmful to the environment, as it can contaminate water sources and soil with arsenic compounds. Arsenic acid is used as a desiccant, a wood preservative, a herbicide, and a chemical intermediate for the synthesis of other arsenic compounds. It is also used in some analytical methods for the detection of arsenic.

References:

• Arsenic acid – Wikipedia
• Arsenic acid | H3AsO4 – PubChem
• Arsenic | Definition, Symbol, Uses, & Facts | Britannica

Arsenic trioxide is another important arsenic compound that has both industrial and medical applications. It is a white solid that can be obtained by roasting arsenic sulfide ores or by treating arsenic acid with a reducing agent. Arsenic trioxide is highly soluble in water and forms arsenious acid, which is a weak acid that can ionize in two steps.

Arsenic trioxide is used as a pigment, a glass additive, a preservative, and a pesticide. It is also used in the production of some alloys, semiconductors, and fireworks. Arsenic trioxide has been used as a poison since ancient times, as it can cause various symptoms such as nausea, vomiting, diarrhea, abdominal pain, convulsions, coma, and death. Arsenic trioxide is also a potent anticancer agent that can induce apoptosis in leukemia cells. It is approved by the FDA for the treatment of acute promyelocytic leukemia (APL), a rare form of blood cancer.

References:

• Arsenic trioxide – Wikipedia
• Arsenic trioxide | As2O3 – PubChem
• Arsenic Trioxide – National Cancer Institute