Acetylene is an unsaturated hydrocarbon CH=CH; a colorless gas. Melting point -81,8°C, it hardens, bypassing the liquid state; its density is 1,171 kg/m3 (in p = 103,3 kN/m2 = 760 mm Hg. article t = 0°C); slightly soluble in water, well soluble in acetone (at 15°C 25 volume of acetylene in 1 volume of acetone). Mixtures of acetylene with air (2.3 to 80.7 per cent A. by volume) are explosive. Acetylene has a narcotic effect.
The combustion of acetylene produces a large amount of heat (14 000 kcal/m3), in this regard, an oxyacetylene flame (maximum temperature of 3150°C) has been successfully used for welding and cutting of ferrous and non-ferrous metals. Acetylene can be transported and stored in steel cylinders under pressure of 1.9 Mn/m2 (19 kgf/cm2) in the form of an acetone solution absorbed by a porous material (e.g., charcoal).
Mode of production
In the laboratory, acetylene is obtained by the action of the water on calcium carbide
CaC2 + 2H2O = C2H2 ↑ + CA(Oh)2
and with dehydration of two methane molecules at temperatures above 1400°C.
Application
Acetylene is used:
Safety
Since acetylene is soluble in water and its mixtures with oxygen can explode in a very wide range of concentrations, it can not be collected in gasometres. Acetylene explodes at a temperature of about 500 °C or a pressure above 0.2 MPa; CPV 2,3-80,7 %, the ignition temperature of 335 °C. the explosion hazard is reduced at diluted acetylene with other gases, such as N2, methane, or propane. Prolonged contact of the acetylene with the copper or silver forms explosive acetylenic copper or silver, which explodes upon impact, or temperature rise. Therefore, acetylene can not be stored in tanks containing copper (for example, the valves of the cylinders).
Acetylene has a slight toxic effect. Acetylene normalized Pdcm.R. = PDK S. S. = 1.5 mg/m3 according to hygienic norms GN 2.1.6.1338-03 “Maximum permissible concentration (MPC) of polluting substances in atmospheric air of populated areas”. Pdcr.z. (working area) is not installed (according to GOST 5457-75 and GN 2.2.5.1314-03), as the concentration limits of distribution of flame in mixtures with air is 2.5-100 %.
It can be stored and transported in steel cylinders filled with an inert porous mass (e.g., charcoal) of white color (with a red inscription “A”) in the form of a solution in acetone under the pressure of 1.5-2.5 MPa.
