diphenylarsenyl cyanide, (C₆H₅)₂AsCN; colorless crystals. Melting point, 31.5°C; boiling point, 346°C; density, 1.3160 g/cm³ (52°C); index of refraction n_D⁵², 1.6153. Insoluble in water but readily soluble in organic solvents. It is hydrolyzed rather rapidly by hot water, and it oxidizes comparatively readily. It is prepared mainly from diphenylchloroarsine (by an exchange reaction with sodium cyanide).

In the form of vapor or smoke, diphenylcyanoarsine strongly irritates the upper respiratory passages (unendurable concentration, 0.25 mg/m³). During World War I it was used by Germany as a poison under the code name Klark II.