Arsine is a colorless gas. It is a reducing agent. It has a weak garlic odor. It easily burns to make arsenic trioxide in excess air or arsenic in small amounts of air. It breaks down to arsenic and hydrogen when heated. It can dissolve in water. It is heavier than air. Arsine reacts violently with oxidizing agents, such as the halogens.
Arsine is made by reacting any arsenic(III) compound with any hydride. It can also be made by reacting any arsenide with an acid. It was first made by reacting zinc, hydrochloric acid, and arsenic trioxide.
Arsine is used to make semiconductors like gallium arsenide. It was looked at as a chemical weapon. It is almost odorless (it kills before one smells it), heavy (spreads along the ground), and colorless. It was unstable though, easily igniting.
Arsine is extremely toxic. 0.00005% (0.5 ppm) can poison people; 0.025% (250 ppm) quickly kills people.