Arsine

Table Of Contents

Arsine Names
Arsine Chemical Definition
Arsine Commercial Availability
Arsine Properties
Arsine Uses and Applications
Health Effects of Arsine Exposure
Treatment for Arsine Exposure
Arsine Precautions

Arsine is flammable and highly toxic gas with formula As H3. It is one of the simpler compounds of arsenic. Reaction of arsenic-containing substances with newly formed hydrogen in water or acids leads to formation of arsine gas. Although arsine is odorless, it is possible to smell like mild garlic when it is present at above about 0.5 ppm

Arsine Names

Arsine is known by many other names like

Arsenic hydride
Hydrogen arsenide
Arseniuretted hydrogen
Arsenious hydride
Arsenic trihydride

Arsine Chemical Definition

Arsines refer to a group of organoarsenic compounds of the formula AsH3−xRx, where R denotes aryl or alkyl. For instance, As(C6H5)3 that is known as Triphenylarsine is an arsine.

Picture 1 – Image of Arsine
Source – encyclopedia.airliquide.com

Arsine Commercial Availability

It is generally commercially available as a liquefied compressed gas in cylinders.

Arsine Properties

Some of the main properties of Arsine are

It is colorless
It is odorless, but smells like mild garlic when present at above about 0.5 ppm
It is slightly soluble in water (20% at 20º C)
It has a molecular weight of 78.0 daltons
It has a boiling point (760 mm Hg) of -62.5ºC.
It is denser than air with gas density of 2.7 (air = 1)
It is extremely flammable and may be ignited by heat, sparks, or flames.
It is a stable compound and decomposes only gradually at room temperature. Humidity, presence of light and specific catalysts (namely aluminum) is some of the factors that determine its rate of decomposition.
It can react dangerously with halogens like fluorine and chlorine or some of their compounds, resulting in explosions
It reacts violently with strong oxidizing agents such as potassium permanganate and nitric acid
As is common with heavy hydrides such as SbH3, H2Te and SnH4, it is unstable thermodynamically though stable kinetically
It can be oxidized with concentrated O2 or dilute O2 concentration. This is a relatively simple process that can be represented by the chemical formula: 2 AsH3 + 3 O2 → As2O3 + 3 H2O
Unlike PH3, this substance does not form stable chains, although H2As–AsH2 and even H2As–As(H)–AsH2 have been spotted. Diarsine is unstable above −100 °C.
Although usually regarded as non-basic, isolable salts of the tetrahedral groups [AsH4] + can be produced by pronation of arsines by superacids.

Arsine Uses and Applications

This substance has varied uses.

It finds its use in the semiconductor industry as a dopant. For silicon and germanium, arsenic is an n-dopant in relation to P. More importantly, arsine is deployed at 700–900 °C to manufacture the semiconductor GaAs by chemical vapor deposition (CVD): Ga(CH3)3 + AsH3 → GaAs + 3 CH4
Acidic properties of As–H bond are often harnessed. Thus, arsine can be deprotonated: AsH3 + NaNH2 → NaAsH2 + NH3
The use of arsine was suggested in chemical warfare because of arsine gas being colorless, almost odorless, and 2.5 times denser than air, ideal for a blanketing effect. Despite such favorable traits, arsine was never formally used as a weapon, due to its high flammability and its reduced efficacy in comparison to non-flammable substitute phosgene.
It is sometimes used in soldering, galvanizing, burnishing, and lead plating.

Health Effects of Arsine Exposure

Exposure to arsine majorly occurs through inhalation. It is non-irritating and creates no urgent warning signs. Symptoms like nausea, dizziness and abdominal pain may be experienced within few hours of contact with 3 ppm of arsine. Exposure to large dose of arsine may lead to additional health implications including convulsions, paralysis, and respiratory failure. Skin contact with liquid arsine can lead to frostbite. Severe exposure to arsine is fatal in most cases. Those who survive may have long-term effects including

Kidney damage
Numbness
Pain in extremities
Neurological problems such as loss of memory, confusion and irritation

Treatment for Arsine Exposure

Blood transfusions and IV (intravenous) fluids may be required. Hemodialysis may be needed in case of some patients.

Arsine Precautions

As no antidote to arsine exists, the best precaution is to avoid it. However, if exposed, one needs to move immediately to an area of fresh air to reduce serious implications. You are advised to change your cloth and wash yourself thoroughly if you think that you are exposed to arsine.

References