CYANOGEN

Chemical Properties

Cyanogen is a colorless, flammable, com- pressed liquefied gas at room temperature. At deadly levels only, it has a pungent, almond-like odor.

Uses

Cyanogen is used as a fumigant, as a fuel gas for welding and cutting metals, as a propellant, and in organic synthesis. It occurs in blast-furnace gases. It is also known to occur at varying concentrations in cassava flour consumed in northern Mozambique.

Production Methods

Cyanogen can be prepared by slowly dropping potassium cyanide solution into copper sulfate solution or by heating mercury cyanide.

Definition

cyanogen: A colourless gas, (CN)₂,with a pungent odour; soluble inwater, ethanol, and ether; d. 2.335g dm–3; m.p. –27.9°C; b.p. –20.7°C.The compound is very toxic. It maybe prepared in the laboratory byheating mercury(II) cyanide; industriallyit is made by gas-phase oxidationof hydrogen cyanide using air over asilver catalyst, chlorine over activatedsilicon(IV) oxide, or nitrogendioxide over a copper(II) salt.Cyanogen is an important intermediatein the preparation of various fertilizersand is also used as a stabilizerin making nitrocellulose. It is an exampleof a pseudohalogen.

General Description

A colorless gas with an odor of almonds. Freezes at -28°C and boils at -20.7°C. Shipped as a liquid confined under its vapor pressure. The gas is heavier than air and a flame can travel back to the source of leak very easily. Prolonged exposure to fire or intense heat may cause the containers to violently rupture and rocket. Used to make other chemicals, as a fumigant, and as a rocket propellant.

Air & Water Reactions

Highly flammable. Soluble in water and slowly decomposed by water to oxalic acid and ammonia.

Reactivity Profile

Colorless, flammable, highly toxic gas. CYANOGEN can react explosively with strong oxidants (dichlorine oxide, fluorene, oxygen, ozone). When heated to decomposition or on contact with acids, acid fumes, water or steam CYANOGEN will react to produce deadly hydrogen cyanide gas and oxides of nitrogen [Sax, 9th ed., 1996, p. 945].

Health Hazard

Cyanogen is a highly poisonous gas having toxic symptoms similar to those of HCN. Acute exposure can result in death by asphyxia. The toxic routes are inhalation and percutaneous absorption. At sublethal concentrations the symptoms of acute toxicity are nausea, vomiting, headache, confusion, and weakness.
Rats exposed to cyanogen exhibited toxic symptoms of respiratory obstruction, lacrimation, and somnolence. Exposure to 350 ppm for 1 hour caused death to 50% of test animals. In humans, exposure to 16 ppm for 5 minutes produced irritation of eyes and nose. Toxicity of cyanogen is considerably lower than that of HCN. Lethal dose in test animals from subcutaneous injection varied between 10 and 15 mg/kg. Ernesto et al. (2002) have reported persistent konzo epidemics and subclinical upper motor neuron damage along with an elevated urinary thiocyanate concentration in school children in Mozambique who were exposed to high cyanogen concentrations from cassava flour.
A subchronic toxicity study conducted on male rhesus monkeys and male albino rats exposed over a period of 6 months (6 hours/day, 5 days/week) indicated marginal toxicity of cyanogen at 25 ppm (Lewis et al. 1984). Total lung moisture content and body weights were significantly lower. The odor threshold level for cyanogen is about 250 ppm.

Fire Hazard

Highly flammable, burns with a purpletinged flame; vapor density 1.8 (air = 1); the vapor may travel a considerable distance to an ignition source and flash back; fireextinguishing procedure: use a water spray to fight fire and keep fire-exposed containers cool; shut off the flow of gas.
Cyanogen forms an explosive mixture with air within the range of 6.6–32%. Liquid cyanogen can explode when mixed with liquid oxygen. When mixed with an acid or water or when heated to decomposition, it produces toxic fumes.

Safety Profile

: A poison by subcutaneous and possibly other routes. Moderately toxic by inhalation. Human systemic effects by inhalation: damage to the olfactory nerves and irritation of the conjunctiva. A systemic irritant by inhalation and subcutaneous routes. A human eyeirritant. Very dangerous fire hazard when exposed to heat, flames (sparks), or oxidizers. To fight fire, stop flow of gas. Potentially explosive reaction with powerful oxidants (e.g., dichlorine oxide, fluorine, oxygen, ozone). When heated to decomposition or on contact with acid, acid fumes, water, or steam will react to produce highly toxic fumes of NOx and CN-. See also other cyanogen entries and CYANIDE.

Potential Exposure

Cyanogen is currently used as an intermediate in organic syntheses; at one time, it was used in poison gas warfare.

storage

Cyanogen is stored outside or in a detached area: cool, dry, and well ventilated, and isolated from acid, acid fumes, and water. It is shipped in high-pressure metal cylinders of.

Shipping

UN1026 Cyanogen, Hazard Class: 2.3; Labels: 2.3-Poisonous gas, 2.1-Flammable gas, Inhalation Hazard Zone B. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner.

Incompatibilities

Chemically unstable in rising tempera- tures. May form explosive mixture with air. Explosive reac- tion with strong oxidizers (e.g., dichlorine oxide, fluorine). Forms toxic gases on contact with acids, including hydro- gen cyanide. Slowly hydrolyzed in water to form hydrogen cyanide, oxalic acid, and ammonia.

Waste Disposal

Return refillable compressed gas cylinders to supplier. Incineration; oxides, or nitrogen are removed from the effluent gas by scrubbers and/or ther- mal devices.

Raw materials

Preparation Products