Cyanide gas

In early times hydrogen cyanide was manufactured from beet sugar residues and recovered from coke oven gas. These methods were replaced by the Castner process in which coke and ammonia were combined with Hquid sodium to form sodium cyanide. If hydrogen cyanide was desired, the sodium cyanide was contacted with an acid, usually sulfuric acid, to Hberate hydrogen cyanide gas, which was condensed for use. This process has since been supplanted by large-scale plants, using catalytic synthesis from ammonia and hydrocarbons. 

The use of black cyanide as a fumigant and rodenticide makes use of the atmospheric humidity action that Hberates hydrogen cyanide gas. It can only be used effectively ia confined spaces where hydrogen cyanide builds up to lethal concentrations for the particular appHcation. Black cyanide is also used ia limited quantities ia the production of pmssiates or ferrocyanides (see Iron compounds). 

The metal-plating baths used are acidic copper sulfate and alkaline silver cyanide. Acid contamination ia the alkaline silver cyanide bath will release extremely poisonous hydrogen cyanide gas. Eor this reason, the two plating setups should be isolated from each other. Both plating baths should be weU... 

Cyanides are dangerously toxic materials that can cause instantaneous death. They occur in a number of industrial situations but are commonly associated with plating operations, and sludges and baths from such sources. Cyanide is extremely soluble and many cyanide compounds, when mixed with acid, release deadly hydrogen cyanide gas. Cyanide is sometimes formed during the combustion of various nitrile, cyanohydrin, and methacrylate compounds. Cyanides (CN ) are commonly treated by chlorine oxidation to the less toxic cyanate (CNO ) form, then acid hydrolyzed to COj and N. Obviously, care should be taken that the cyanide oxidation is complete prior to acid hydrolysis of the cyanate. 

Hazards of Combustion Products Toxic hydrogen cyanide gas may form in fires Behavior in Fire Not pertinent Ignition Tenqterature Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials No reaction Stability During Transport Stable, in presence of moisture, toxic hydrogen cyanide gas may collect in enclosed spaces Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor cf Polymerization Not pertinent. 

Chemical Reactivity - Reactivity with Water. When potassiiun cyanide dissolves in water, a mild reaction occurs and poisonous hydrogen cyanide gas is released. The gas readily dissipates, however if it collects in a confined space, then workers may be exposed to toxic levels. If the water is acidic, toxic amounts of the gas will form instantly Reactivity with Common Materials Contact with even weak acids will result in the formation of deadly hydrogen cyanide gas Stability During Transport Stable Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

Caution Potassium cyanide is a potent poison, which should always be handled with gloves in a well-ventilated hood. Contact with acid releases toxic hydrogen cyanide gas. 

Cyanide-based metal finishing solutions usually operate at basic pH levels to avoid decomposition of the complexed cyanide and the formation of highly toxic hydrogen cyanide gas. 

It generates toxic levels of sulfide or cyanide gas when exposed to a pH range of 2 to 12.5. 

No studies were located regarding quantitative absorption in humans after dermal exposure to cyanide gas or common inorganic salts. Evidence that cyanide can be absorbed through the skin of humans is provided in case reports of toxic effects in humans after accidental dermal contact with cyanide (see Section 2.2.3). 

Environmental Fate. The environmental fate of hydrogen cyanide gas in air is well studied (Cicerone and Zellner 1983 Fritz et al. 1982) however, it would be useful if the role of particulate cyanides (e.g., sodium cyanide, potassium cyanide) in determining the fate of total cyanides in the air was known. Given that hydrogen cyanide occurs in the atmosphere from both natural and anthropogenic processes (Cicerone... 

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