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The solubility of gas obeys Henry's law, that is, the amount of a dissolved gas in a liquid is proportional to its partial pressure. Therefore, placing a solution under reduced pressure makes the dissolved gas less soluble. Sonication and stirring under reduced pressure can usually enhance the efficiency.
The system can be flushed with an inert gas to reduce the concentration of oxygen so that when the flammable gas is admitted, an ignitable mixture cannot form. In NFPA 56, [1] this is known as purge-into-service. In combustion engineering terms, the admission of inert gas dilutes the oxygen below the limiting oxygen concentration.
Air-free techniques refer to a range of manipulations in the chemistry laboratory for the handling of compounds that are air-sensitive. These techniques prevent the compounds from reacting with components of air , usually water and oxygen ; less commonly carbon dioxide and nitrogen .
A new, emerging flue gas desulfurization technology has been described by the IAEA. [16] It is a radiation technology where an intense beam of electrons is fired into the flue gas at the same time as ammonia is added to the gas. The Chendu power plant in China started up such a flue gas desulfurization unit on a 100 MW scale in 1998.
A physical change involves a change in physical properties. Examples of physical properties include melting, transition to a gas, change of strength, change of durability, changes to crystal form, textural change, shape, size, color, volume and density. An example of a physical change is the process of tempering steel to form a knife blade.
Most liquids freeze by crystallization, formation of crystalline solid from the uniform liquid. This is a first-order thermodynamic phase transition, which means that as long as solid and liquid coexist, the temperature of the whole system remains very nearly equal to the melting point due to the slow removal of heat when in contact with air, which is a poor heat conductor.
A certain amount of energy, which may be large enough, is required to remove an electron from an atom or a molecule in its ground state. [12] [13] In chemi-ionization processes, the energy consumed by the ionization must be stored in atoms or molecules in a form of potencial energy or can be obtained from an accompanying exothermic chemical change (for example, from a formation of a new ...
Methanation is an important step in the creation of synthetic or substitute natural gas (SNG). [7] Coal or wood undergo gasification which creates a producer gas that must undergo methanation in order to produce a usable gas that just needs to undergo a final purification step.