What Is Hydrogen Cyanide?
Hydrogen cyanide is liquid under standard conditions. Hydrogen cyanide easily disperses evenly in the air and can burn in the air. When the content of hydrogen cyanide in the air reaches 5.6% to 12.8%, it is explosive. Hydrocyanic acid is highly toxic. The clinical manifestations of acute hydrogen cyanide poisoning are obvious bitter almond smell in the exhaled breath of patients, and mild poisoning mainly manifests as chest tightness, palpitations, accelerated heart rate, headache, nausea, vomiting, and blurred vision. Severe poisoning is mainly manifested in a deep coma, shallow breathing, paroxysmal seizures, and even tonic spasticity. In World War II, Nazi Germany often used hydrogen cyanide as a killer gas for gas chambers.
Hydrogen cyanide
- Chinese name
- Hydrogen cyanide
- English name
- hydrogen cyanide
- nickname
- Hydrocyanic acid
- Chemical formula
- HCN
- Molecular weight
- 27.03
- CAS Registry Number
- 74-90-8
- Melting point
- -13.4 (259.75 K, 7.88 ° F)
- Boiling point
- 26 ° C (299.15 K, 78.8 ° F)
- Water soluble
- Soluble in water
- Density
- 0.697 (18 )
- Exterior
- Colorless gas or liquid with bitter almond smell
- Flash point
- -17.8
- Application
- Electroplating, mining
- Risk description
- Inorganic acute drugs, flammable liquid
- Hydrogen cyanide is liquid under standard conditions. Hydrogen cyanide easily disperses evenly in the air and can burn in the air. When the content of hydrogen cyanide in the air reaches 5.6% to 12.8%, it is explosive. Hydrocyanic acid is highly toxic. The clinical manifestations of acute hydrogen cyanide poisoning are obvious bitter almond smell in the exhaled breath of patients, and mild poisoning mainly manifests as chest tightness, palpitations, accelerated heart rate, headache, nausea, vomiting, and blurred vision. Severe poisoning is mainly manifested in a deep coma, shallow breathing, paroxysmal seizures, and even tonic spasticity. In World War II, Nazi Germany often used hydrogen cyanide as a killer gas for gas chambers.
Physical and chemical properties of hydrogen cyanide
Physical properties of hydrogen cyanide
- Colorless transparent liquid, volatile, with a bitter almond odor. Miscible with ethanol, ether, glycerin, ammonia, benzene, chloroform and water. [1-2]
- Auto-ignition vapor pressure at different temperatures:
| 0 32T | 35.23kPa [3] |
| 10 50T | 53.32kPa [3] |
| 20 ° C (68T) | 81.3lkPa [3] |
| 30 86T | 121.3kPa [3] |
Hydrogen cyanide chemical properties
- The weak acid reacts with the base to form a salt. When its aqueous solution is boiled, it partially hydrolyzes to form ammonium formate. Under basic conditions, it combines with aldehydes and ketones to form cyanohydrins, and interacts with acetone to generate acetone cyanohydrins. Gaseous hydrocyanic acid generally does not polymerize, but when moisture condenses, a polymerization reaction occurs, and air (oxygen) does not promote the polymerization reaction. Liquid hydrocyanic acid or its aqueous solution can cause polymerization under alkaline, high temperature, long-term storage, exposure to light and radiation, discharge, and electrolysis. After the polymerization begins, the heat generated will cause a chain reaction of the polymerization, thereby accelerating the progress of the polymerization reaction, and simultaneously releasing a large amount of thermal energy, causing a violent explosion. The explosion limit is 5.6% to 40% (volume). Its steam burns into a blue flame. In the presence of hydrocyanic acid in the air, a blue reaction was measured with a benzidine-copper acetate test paper, and a change from orange to pink was measured with a methyl orange-mercury (II) test paper. Yellow turns brown. Very toxic. [2]
- Chemical reaction equation:
- NH 3 + C = HCN + H 2 Reaction conditions: intense heat.
- Because HCN is weaker than carbonic acid and stronger than bicarbonate, it cannot react with carbonates to emit CO 2. On the contrary, cyanide will react as follows to absorb CO 2 and generate bicarbonate.
- CN-+ CO 2 + H 2 O = HCN + HCO 3-
Hydrogen cyanide toxicity test
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- [4-29]
Toxicological information of hydrogen cyanide
- The maximum allowable concentration is 0.3 mg / m 3 . The lethal dose is 1 mg / kg (body weight). Acute toxicity LC 50 : 357 mg / m 3 (mouse inhalation, 5 min) [30]
- Cyanide ions can inhibit the activities of 42 enzymes in tissue cells, such as cytochrome oxidase, peroxidase, decarboxylase, succinate dehydrogenase, and lactate dehydrogenase. Among them, cytochrome oxidase is the most sensitive to cyanide. Cyanide ions can rapidly interact with oxidized cytochrome oxidase
- Toxic effects: the harm of cyanide to the human body is divided into two aspects: acute poisoning and chronic effects. The acute poisoning caused by cyanide can be divided into mild, moderate and severe. Mild poisoning manifests as eye and upper respiratory tract irritation symptoms, with bitter almond smell, numbness of lips and throat, and then nausea, vomiting, tremor, etc .; moderate poisoning manifests as sigh-like breathing, and skin and mucous membranes are often bright red Other symptoms worsened; severe poisoning manifested as loss of consciousness, tonicity and paroxysmal seizures, until angled arch reflex, blood pressure decreased, urine and fecal incontinence, often accompanied by cerebral edema and respiratory failure. The chronic effects of hydrocyanic acid on the human body are manifested as neurasthenia syndrome, such as dizziness, headache, fatigue, chest compression, muscle pain, abdominal pain, etc., and may have eye and upper respiratory tract irritation symptoms. After long-term contact with the skin, it can cause a rash, manifested as macular rash, pimples, and extremely itchy. [31]
- Example and analysis of hydrogen cyanide poisoning: At around 10:00 am on July 27, 1992, the hydrocyanic acid pipeline of the cyanohydrin section of a chemical plant in Shanghai was blocked. Zhou discovered that the hydrocyanic acid pipeline with the plug valve removed had a slight drip, that was, he rushed to the platform on the fourth floor, and wanted to close the plug valve of the drip pipeline, but accidentally opened the main plug valve of the hydrocyanic acid tank. Causes 60 kg of hydrogen cyanide to leak out of the tank. During the call evacuation process, some workers in other sections in the downwind direction had no time to escape and inhaled a large amount of hydrogen cyanide gas, resulting in 4 people with acute hydrogen cyanide poisoning, including 1 who died of acute hydrogen cyanide poisoning with brain trauma.
- Dosing:
- (1) According to the volume between the fumigation chambers, calculate the amount of NaCN and the number of cylinders (glazed water tanks) to be used, and distribute the cylinders evenly in the warehouse. [3]
- (2) For weighing sodium cyanide, workers must wear overalls, long rubber boots, goggles, masks, and rubber gloves. Each serving should not exceed 15kg. Put it on the side of the vat after dispensing. [3]
- (3) When weighing concentrated sulfuric acid and dispensing concentrated sulfuric acid, it is safer to use the cylinder suction method, and put it on the side of the reaction tank after the dispensing. [3]
- (4) Pour sufficient water into the reaction tank, then slowly pour concentrated sulfuric acid and stir. [3]
- (5) When administering peony, the medicine should be injected from the warehouse to the outside of the warehouse. Avoid confusion. [3]
- (6) Close the warehouse immediately after administration. [3]
- Concentration and leak detection: The most commonly used and more accurate method is the "benzidine" method: a 0.1% benzidine acetate solution and a 0.3% copper acetate solution are prepared and stored in brown bottles, and each of the two solutions is mixed before use ( Use within 15 minutes). Cut through the filter paper into 6cm × 12cm strips to soak up the liquid medicine. The paper strip with liquid medicine is blue after encountering cyanic acid gas. [3]
- Ventilation, detoxification and residue disposal: After the sealing time is reached, open the warehouse transom to allow the indoor poisonous gas to escape. Only when the inspection is non-toxic, personnel can enter the fumigation place. After the poisoning is completed, lift the reaction tank away from the warehouse and dig deep. (1.2 ~ 15m), the burial point should be more than 50m away from the riverside well. [3]
Symptoms of hydrogen cyanide poisoning
Mild hydrogen cyanide poisoning
- Eye and upper respiratory tract irritation symptoms, headache, dizziness, chest tightness, nausea, etc. The bitter almond smell in the exhaled breath can relieve itself. [32]
Moderate poisoning by hydrogen cyanide
- Nausea, vomiting, chest pressure, shortness of breath, bright red or pale skin and mucous membranes.
Severe hydrogen cyanide poisoning
- Causes hydrocephalus in the brain, compression of nerves, loss of consciousness, fatigue, tonicity or paroxysmal convulsions, muscle relaxation throughout the body, disappearance of reflexes, breathing and heartbeat can be stopped at any time.
- [32]
First aid measures for hydrogen cyanide
- Remove the patient to fresh air, remove contaminated clothing, rinse the contaminated skin with clean water and 0.5% sodium thiosulfate. Oral poisoning can use 0.2% potassium permanganate, 5% sodium thiosulfate, or 3% peroxide. Thorough gastric lavage with hydrogen, pay attention to sedation, keep warm and inhale oxygen. Isoamyl nitrite is injected with 3% sodium nitrite 10-15ml in a timely manner. Artificial breathing should be performed for heartbeat and respiratory arrest until it is sent to the hospital. [32]
Hydrogen cyanide medical measures
- Sodium nitrite-sodium thiosulfate therapy. For moderate and mild patients, inhalation of isoamyl nitrite and intravenous injection with 3% sodium nitrite, and then injection of 50% sodium thiosulfate 10-20ml. For severely ill patients, intramuscular injection of 10% 4-dimethylaminobenzoic acid 2ml, followed by 10g of sodium thiosulfate; if the symptoms are repeated, it can be repeated half an hour later. At the same time as the above treatment, give oxygen, long coma, severe hypoxia, and actively prevent cerebral edema. [32]
Application fields of hydrogen cyanide
Main uses of hydrogen cyanide
- Hydrogen cyanide is mainly used in electroplating industry (copper plating, gold plating, silver plating), mining industry (extracting gold and silver), cabins and warehouses for fumigating rodents, and manufacturing various resin monomers such as acrylic resins and methacrylic Ester and other industries can also be exposed to this substance during the production of cyanide. [33]
Hydrogen cyanide prevention object
- Hydrocyanic acid is one of the earliest widely used fumigants in modern times. Hydrocyanic acid can be used to control various insect states (except mite dormant bodies) for various storage pests. The toxicity of the animal is stronger than that of the active plant, so it is a better fumigant for fumigation of seedlings and seeds in a sufficiently dry dormant body. Normal seed treatment with hydrocyanic acid will not affect its germination rate. Treatment of dormant seedlings with hydrocyanic acid has a good effect in controlling worms, but it must be washed with water after fumigation to prevent pesticide damage. The medicine is easily soluble in water and dissolved into a dilute acid in water, and cannot be safely used for fruits and vegetables with high water content. Hydrocyanic acid is an excellent fumigant commonly used for many storages, grains, grains, etc. Many objects have strong adsorption of hydrocyanic acid. If the smoked articles are dried, this effect is reversible. Adsorption, which limits the penetration of the drug, it is recommended to use reduced pressure fumigation. Because hydrocyanic acid is highly toxic to warm-blooded animals, it is often used as a rodenticide for ocean-going vessels. [3]
How to use hydrogen cyanide
- 1. Liquid hydrocyanic acid direct application: This dosage form is more convenient, safe, and labor-saving. Its operation method is similar to that of bromide. When using it, you should pay attention to it. Return to the original factory to avoid explosion during use. [3]
- 2. Reaction with cyanate to generate cyanide gas:
- (1) Calcium cyanide enters water to generate cyanide gas: The use of calcium cyanide requires 15 to 26 ° C. Relative humidity of 80% to 90% is better. The method is to evenly spread calcium cyanide on paper and let it decompose by itself. The thickness of the tile is 1 to 2mm. In dry weather, spray water appropriately around the medicine. ; Such as calcium cyanide containing 50% cyanide is generally used 25 ~ 35g / m3. [3]
- (2) Sodium cyanide: Sodium cyanide used to be the most widely used fumigant in China. The NaCN for fumigation must have a purity of more than 98%. The density of the concentrated sulfuric acid reacted with it is 1.84 (Baume degree 66). The ratio of sodium cyanide to concentrated sulfuric acid and water is (W: W: W) l: 1.5: 3. Theoretically, 1 part of sodium cyanide should be mixed with 1 part of concentrated sulfuric acid, but excess acid can accelerate the generation of cyanic acid. Mixing water and concentrated sulfuric acid can exotherm and accelerate the reaction, but the temperature should not be higher than 60 70 when heating Otherwise, sulfuric acid will be reduced to CO2 and SO2, which will reduce the production of HCN. If too much water is added, HCN cyanogen gas will generate less water vapor and more slowly, which will affect the fumigation effect. Almost all products are carbon monoxide. Therefore, the ratio of the ya system is of great significance to the fumigation effect; the recommended dosage of sodium cyanide NaCN is 30 40g / m3 (10 ).
- (3) Potassium cyanide (KCN) is expensive and is generally used as a drug in laboratories. [3]
Caution for hydrogen cyanide
Health hazards of hydrogen cyanide
- Inhibits respiratory enzymes, causing intracellular suffocation. Acute poisoning: Inhalation of high concentrations of hydrogen cyanide gas within a short period of time can immediately stop breathing and die. Non-sudden death patients are clinically divided into 4 stages: prodromal period with mucosal irritation, deepening of breathing, fatigue, headache; oral tongue tip, oral numbness, etc. Dyspnea has dyspnea, elevated blood pressure, and bright red skin and mucous membranes. Seizures, coma, and respiratory failure occurred during the convulsions. During the paralysis period, the whole body muscles relax, and the breathing and heartbeat stop and die. Can cause eye and skin burns, poisoning caused by absorption. Chronic effects: neurasthenia syndrome, dermatitis. [34]
First aid measures for hydrogen cyanide
- Skin contact: Remove contaminated clothing immediately and rinse thoroughly with running water or 5% sodium thiosulfate solution for at least 20 minutes. Seek medical attention.
- Eye contact: Raise the eyelids immediately and rinse thoroughly with plenty of running water or saline for at least 15 minutes. Seek medical attention.
- Inhalation: Quickly leave the scene to fresh air. Keep your airways open. If breathing is difficult, give oxygen. When breathing is stopped, immediately perform artificial respiration (do not use mouth to mouth) and chest compressions. Give inhaled isoamyl nitrite and seek medical attention.
- Ingestion: Drink plenty of warm water and induce vomiting. Wash the stomach with 1: 5000 potassium permanganate or 5% sodium thiosulfate solution. Seek medical attention. [34]
Hydrogen cyanide fire extinguishing method
- Shut off the air supply. If the gas source cannot be shut off, the flame at the leak shall not be extinguished. Firefighters must wear special protective clothing for the whole body, oxygen breathing apparatus, and operate from a safe distance or protected place. Fire extinguishing agent: dry powder, alcohol-resistant foam, carbon dioxide. Water extinguishing is not effective, but water containers must be kept cool. Vaporized with mist water. [34]
Hydrogen cyanide safety common sense
- 1. Contact opportunity: It is mainly used in the electroplating industry (copper plating, gold plating, silver plating), the mining industry (extracting gold and silver), cabins, warehouses, and fumigating rodents, manufacturing various resin monomers such as acrylic resins, nails Industries such as acrylic acrylate resins can also be exposed to this substance during the production of cyanide. [31]
- 2. Local treatment: Isolate isoamyl nitrite 1-2 ampoules in a handkerchief, shatter it in front of the nose and mouth, and perform artificial respiration while paying attention to vital signs. [31]
- 3. Selection of gas mask: Because of the strong toxicity of hydrogen acid gas, you must be cautious when choosing and wearing a gas mask. GB2890-82 IL type canisters are commonly used in China. When using other types of canisters, you should read the instructions carefully And production date, generally the effective filter time is only about 50 minutes in the concentration of 3g / m3 cyanic acid gas; before using, apply chlorinated bitcoin to test the effectiveness of the filter can and whether to wear the gas mask. It is recommended that a large fumigation team have at least one self-contained breathing device when fumigating with hydrocyanic acid, in case of accident. [3]
- Remarks: GB2890-1995 replaced GB289o-82. The National Technical Supervision Bureau 1995-1 06-28 approved the implementation of 1996-011 01 [35]