HCN-1 - 19 HYDROGEN CYANIDE Hydrogen cyanide HCN is also...

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347 1 9 HYDROGEN CYANIDE Hydrogen cyanide‚ HCN‚ is also known as hydrocyanic acid‚ prussic acid and formonitrile. Although HCN is a colorless liquid‚ iron cyanide is blue (prussian blue) and its presence as a slight contaminant usually gives HCN a bluish tint that led to the German name Blausäure – blue acid. Selected physical properties of hydrogen cyanide are shown in Table 19.1. Table 19.1. Physical Properties of Hydrogen Cyanide Molecular Formula Molecular Weight Melting Point Triple Point Boiling Point (1 atm) Density‚ g/ml 0 °C 10 °C 20 °C Specific Gravity of Aqueous Solutions (@18°C compared to water @ 18°C) 10.04% 20.29% 60.23% Vapor Specific Gravity (@31°C‚ air = 1) Vapor Pressure‚ kPa -29.5 °C 0.0 °C 27.2 °C Liquid Viscosity @ 20.2 °C 27.03 -13.24°C -13.32 °C 25.70 °C 0.7150 0.7017 0.6884 0.9838 0.9578 0.8290 0.947 6.697 35.24 107.6 0.2014
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348 SYNTHETIC NITROGEN PRODUCTS Table 19.1. Physical Properties of Hydrogen Cyanide - Specific Heat‚ J/mol -33.1°C‚ Liquid 16.0 °C‚ Liquid 27.0 °C‚ Gas Heat of Formation (@ 25°C‚ 1 atm)‚ kJ/mol Gas @ 25°C Liquid @ 25°C Heat of Fusion @ -14 °C‚ kJ/mol Latent Heat‚ kJ/mol Heat of Combustion‚ net‚ kJ/mol Conductivity‚ S/cm 6 Heat of Vaporization‚ kJ/mol Heat of Polymerization‚ kJ/mol Flash cup‚ closed cup‚ °C Autoignition Temperature, °C continued 58.36 70.88 36.03 -130.5 -105.4 7‚100 23.8 642 3.3 x 10- 25.2 42.7 -17.8 6 to 41 538 19.1. SAFETY Cyanides are non-cumulative‚ protoplasmic poisons. That means they can be detoxified readily. Cyanide combines with those enzymes at the blood tissue interfaces that regulate oxygen transfer to the cellular tissues. Unless the cyanide is removed‚ death results through insufficient oxygen in the cells 129 . The warning signs of cyanide poisoning include dizziness‚ numbness‚ headache‚ rapid pulse‚ nausea‚ reddened skin and bloodshot eyes. More prolonged exposure can cause vomiting and labored breathing followed by unconsciousness; cessation of breathing; rapid‚ weak heat beat; and then death. Sever exposure by inhalation can cause immediate unconsciousness. This rapid knockdown power without an irritating odor makes hydrogen cyanide very dangerous 129 . Many people can detect hydrogen cyanide by odor or taste sensation at a concentration of 1 ppm in air while most people can detect 5 ppm. But HCN does not have an offensive odor‚ and a few people cannot smell it even at toxic levels. OSHA has set 4.7 ppm as the maximum‚ average safe exposure limit for a 15-minute period. Exposure to 20 ppm of HCN in air causes slight warning symptoms after several hours; 50 ppm causes disturbances within an hour; 100 ppm is dangerous for exposures of 30 to 60 minutes; and 300 ppm can be rapidly fatal unless prompt‚ effective first aid is administered. A small concentration of cyanide (0.02 to 0.04 mg/L) always exists in a person’s body‚ and the body has a mechanism for continuous removal of small amounts of cyanide 129 .
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HCN-1 - 19 HYDROGEN CYANIDE Hydrogen cyanide HCN is also...

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