Arsine (data page)
Arsine (AsH3) is a colorless, extremely toxic, flammable, and pyrophoric gas. It is one of the simplest hydrides of arsenic. Despite its deadly nature, it finds some use in the semiconductor industry, especially for ion implantation processes. Arsine has a garlic-like or faintly onion-like odor that may not be noticeable at dangerous concentrations.
Properties:
- Chemical Formula: AsH3
- Molar Mass: 77.945 g/mol
- Appearance: Colorless gas
- Odor: Faint garlic-like or onion-like (often undetectable at hazardous concentrations)
- Density: 3.48 g/L (at 0 °C and 1 atm)
- Melting Point: -116.3 °C (-177.3 °F; 156.8 K)
- Boiling Point: -62.5 °C (-80.5 °F; 210.7 K)
- Solubility in Water: Slightly soluble
- Acidity (pKa): ~20 (weak acid)
- Flammability: Pyrophoric (ignites spontaneously in air under certain conditions)
Hazards:
Arsine is a highly dangerous systemic poison. It causes hemolysis, the destruction of red blood cells, leading to kidney failure and death. Symptoms of arsine poisoning may include headache, dizziness, weakness, abdominal pain, nausea, vomiting, and jaundice. There may be a delay of several hours between exposure and the onset of symptoms. Arsine's toxicity is primarily due to its ability to bind to hemoglobin in red blood cells, causing their destruction. Even low concentrations can be fatal.
Production:
Arsine can be produced through several methods, including:
- The reaction of arsenic-containing compounds with strong reducing agents, such as nascent hydrogen (e.g., from the reaction of zinc with hydrochloric acid).
- Hydrolysis of metal arsenides (e.g., magnesium arsenide).
- As a byproduct in certain industrial processes where arsenic is present as an impurity, such as metal refining and the manufacture of certain pesticides.
Uses:
The primary use of arsine is in the semiconductor industry as a precursor for the deposition of arsenic-containing thin films, used in the manufacture of microelectronic devices. Arsine is also used in ion implantation to dope semiconductors with arsenic.
Safety Precautions:
Because of its extreme toxicity and pyrophoric nature, arsine must be handled with extreme caution. This includes:
- Using proper personal protective equipment (PPE), including respirators and protective clothing.
- Working in well-ventilated areas or using fume hoods.
- Implementing strict engineering controls to prevent leaks and releases.
- Having readily available detection equipment and emergency procedures in place.
- Proper training for all personnel who handle arsine.
Storage:
Arsine should be stored in sealed containers in a cool, dry, and well-ventilated area, away from incompatible materials such as strong oxidizers. Cylinders of arsine should be handled and stored with appropriate safety precautions.