Toxic Gases 14 Carbon Monoxide

Hess s law is very convenient for obtaining values of AH for reactions that are difficult to carry out in a calorimeter. Consider, for example, the formation of the toxic gas carbon monoxide from the elements... 

Consider the two compounds that contain carbon and oxygen. The carbon contained in wood is converted to carbon dioxide when wood burns completely. The formula for this product is CO2. If the carbon in wood burns incompletely, the highly toxic gas carbon monoxide is formed. What is the formula for carbon monoxide ... 

A common symbol for volume percent is % (v/v). Commercial rubbing alcohol, for example, is an aqueous solution of isopropyl alcohol (a three-carbon alcohol) that contains 70 volumes of isopropyl alcohol per 100. volumes of solution, and the label indicates this as 70% (v/v). Parts-by-volume concentrations are most often used for liquids and gases. Minor atmospheric components occur in parts per million by volume (ppmv). For example, there are about 0.05 ppmv of the toxic gas carbon monoxide (CO) in clean air, 1000 times as much (about 50 ppmv of CO) in air over urban traffic, and 10,000 times as much (about 500 ppmv of CO) in cigarette smoke. 

One fairly common reaction is the oxidation reaction, in which an oxygen atom is added to the chemical structure of the molecule. The most conunon of the oxidation reactions is combustion, in which a molecule is heated to a high temperature in the presence of air and decomposed to produce CO and water. This reaction forms the basis by which energy is generated from fossil resources, with the production of CO as a by-product. Combustion of fossil resources has led to an increase in the atmospheric content of CO. However, under conditions of restricted oxygen, the oxidation of hydrocarbons C H to carbon dioxide is not complete, and the toxic gas carbon monoxide may also be formed (1 atom of C and 1 atom of O forms CO) (Chapter 3). 

Carbon monoxide (CO) is generated in incomplete combustion processes. In households the main sources are all kinds of fuel burners (fuel oil, wood, natural gas, coal etc.) and automotive exhaust gas. Carbon monoxide is an odorless and invisible gas, and, due to its affinity to hemoglobin, which is higher than that of oxygen, it reduces the blood s capacity to carry oxygen. Hence it is toxic, especially for unborn and small children as well as for the elderly or people with heart problems or anemia. Even small amounts of CO can be harmful. Tab. 5.6 gives an overview of the relation between CO concentration and the corresponding symptoms of intoxication. 

Dewaxing (Figure 4.17) processes also produce heater stack gas (carbon monoxide, sulfur oxides, nitrogen oxides, and particulate matter) as well as hydrocarbon emission such as fugitive propane and fugitive solvents. Steam stripping wastewater (oil and solvents) and solvent recovery wastewater (oil and propane) are also produced. The fugitive solvent emissions may be toxic (toluene, methyl ethyl ketone, methyl isobutyl ketone). 

Caution. Due to the toxicity of mercury compounds, both starting materials and products must be handled with care to avoid any skin contact. Due to the toxicity of carbon monoxide gas, this reaction must also be carried out in a well-ventilated hood. 

In the 19th-century days of gas lamps, water gas was frequently used for domestic purposes, a practice fraught with danger because of the extreme toxicity of carbon monoxide (see Chapter 19). The ratio of hydrogen to carbon monoxide in water gas... 

Moss, R.H., C.FJackson, and J.Seiberlich. 1951. Toxicity of carbon monoxide and hydrogen cyanide gas mixtures. Arch. Ind. Hyg. Occup. Med. 4 53-64. 

Carbon monoxide. Carbon monoxide is a colorless, odorless gas, liquefying at -191.5°. It is readily available, at pressures of up to about 100 bar, in a variety of cylinder sizes, so that experiments can be run at 80 bar without a compressor. The acute toxicity of carbon monoxide reflects its high affinity for hemoglobin. It is stated" that 400-500 ppm of carbon monoxide in air can be breathed for an hour without appreciable effect, while levels above 1000 ppm are dangerous, and at more than 4000 ppm it causes death within an hour. The previously cited reference gives a Threshold Limit Value of 50 ppm. Carbon monoxide must always be used in an efficient fume cupboard, keeping emissions into the laboratory atmo-... 

HAZARD RISK Slight fire hazard when exposed to heat incompatible with acetone, strong alkalis, chemically active metals, dinitrogen tetraoxide, fluorine, potassium-tert-butoxide, sodium, sodium hydroxide, methanol, sodium methoxide, triisopropyl phosphine decomposition emits toxic fumes of hydrogen chloride gas, phosgene gas, carbon monoxide and carbon dioxide can be explosive when confined with water poses explosive hazard if present in boiler feed or cooling water NFPA code H 2 F 0 R 0. 

Despite the results presented above, there has been reluctance to consider carbon monoxide for microbiological control. This may result from fears regarding its inherent toxicity as well as from the public perception of the use of toxic compounds to treat wine. Indeed, carbon monoxide is a toxic, colorless, and odorless gas whose detection requires specialized equipment. However, in terms of potential health risks, SO2 is considerably more toxic than carbon monoxide. Toxicity data for the two show that the IDLH (Immediately Dangerous to Life and Health) level for CO is 1500 mg/L, whereas for SO2, it is only 100 mg/L (Sigma-Aldrich Library of Chemical Safety Data, 1988). 

Toxic substances are ones which impede or prevent the function of one or more organs within the body, such as the kidneys, liver and heart. A toxic substance is, therefore, a poisonous one. Lead, mercury, pesticides and the gas carbon monoxide are toxic substances. Carcinogenic substances are ones which are known or suspected of promoting abnormal development of body cells to become cancers. Asbestos, hard wood dust, creosote and some mineral oils are carcinogenic. It is very important that the health and safety rules accompanying the substance are strictly followed. 

Outside of carbon monoxide for which the toxicity is already well-known, five types of organic chemical compounds capable of being emitted by vehicles will be the focus of our particular attention these are benzene, 1-3 butadiene, formaldehyde, acetaldehyde and polynuclear aromatic hydrocarbons, PNA, taken as a whole. Among the latter, two, like benzo [a] pyrene, are viewed as carcinogens. Benzene is considered here not as a motor fuel component emitted by evaporation, but because of its presence in exhaust gas (see Figure 5.25). 

To enable interchangeabiUty of the SNG with natural gas, on a calorific, flame, and toxicity basis, the synthetically produced gas consists of a minimum of 89 vol % methane, a maximum of 0.1% carbon monoxide, and up to 10% hydrogen. The specified minimum acceptable gross heating value is approximately 34.6 MJ/m (930 Btu/fE). 

Nickel Carbonyl The extremely toxic gas nickel carbonyl can be detected at 0.01 ppb by measuring its chemiluminescent reaction with ozone in the presence of carbon monoxide. The reaction produces excited nickel(II) oxide by a chain process which generates many photons from each pollutant molecule to permit high sensitivity (315). 

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