Oxidant gases

For tire situation in figure C2.8.5 a), tire catliodic reaction is tire reduction of oxide/gas or... 

Regardless of the techniques used to purify the KA oil, several waste streams are generated during the overall oxidation—separation processes and must be disposed of. The spent oxidation gas stream must be scmbbed to remove residual cyclohexane, but afterwards will stiU contain CO, CO2, and volatile hydrocarbons (especially propane, butane, and pentane). This gas stream is either burned and the energy recovered, or it is catalyticaHy abated. 

Hot Corrosion. Hot corrosion is an accelerated form of oxidation that arises from the presence not only of an oxidizing gas, but also of a molten salt on the component surface. The molten salt interacts with the protective oxide so as to render the oxide nonprotective. Most commonly, hot corrosion is associated with the condensation of a thin molten film of sodium sulfate [7757-82-6], Na2S04, on superaHoys commonly used in components for gas turbines, particularly first-stage turbine blades and vanes. Other examples of hot corrosion have been identified in energy conversion systems, particularly coal gasifiers and direct coal combustors. In these cases the salt originates from alkali impurities in the coal which condense on the internal... 

Low humidity ethylene oxide gas sterilisa tion procedures and moisture-proof packaging for polyglycoHc acid products are necessary because of the susceptibihty to degradation resulting from exposure to moisture and gamma sterilisation. 

K. Ihokura and J. Watson, The Stannic Oxide Gas Sensor, CRC Press, Ann Arbor, Mich., 1994. 

Carhon monoxide Fuming of metallic oxides, gas-operated fork trucks Primary metals steel and aluminum Reduction in oxygen-carrying capacity of blood... 

The logaritlrmic law is also observed when the oxide him is an electrical insulator such as AI2O3. The transport of elecuons tlrrough the oxide is mainly due to a space charge which develops between tire metal-oxide interface and the oxide-gas interface. The incorporation of oxygen in the surface of tire oxide requhes the addition of electrons, and if this occurs by a charging process... 

If the oxidizing gas is pure oxygen, and iNi2+ remains approximately constant over the oxide thickness... 

The Ni-base alloy surface is exposed to an oxidizing gas, oxide nuclei form, and a continuous oxide film forms (Ni) (Cr203, etc.)- This oxide film is a protective layer. The metal ions diffuse to the surface of the oxide layer and combine with the molten Na2S04 to destroy the protective layer. Ni2S and Cr2S3 results sulfidation) ... 

Reaetion with eonstruetion materials, e.g. nitrie aeid ean produee nitrie oxide gas on eontaet with eopper in pipes or eopper windings in motors of eanned pumps ... 

Oxide movements are determined by the positioning of inert markers on the surface of the oxideAt various intervals of time their position can be observed relative to, say, the centreline of the metal as seen in metal-lographic cross-section. In the case of cation diffusion the metal-interface-marker distance remains constant and the marker moves towards the centreline when the anion diffuses, the marker moves away from both the metal-oxide interface and the centreline of the metal. In the more usual observation the position of the marker is determined relative to the oxide/ gas interface. It can be appreciated from Fig. 1.81 that when anions diffuse the marker remains on the surface, but when cations move the marker translates at a rate equivalent to the total amount of new oxide formed. Bruckman recently has re-emphasised the care that is necessary in the interpretation of marker movements in the oxidation of lower to higher oxides. 

Several authors " have suggested that in some systems voids, far from acting as diffusion barriers, may actually assist transport by permitting a dissociation-recombination mechanism. The presence of elements which could give rise to carrier molecules, e.g. carbon or hydrogen , and thus to the behaviour illustrated in Fig. 1.87, would particularly favour this mechanism. The oxidant side of the pore functions as a sink for vacancies diffusing from the oxide/gas interface by a reaction which yields gas of sufficiently high chemical potential to oxidise the metal side of the pore. The vacancies created by this reaction then travel to the metal/oxide interface where they are accommodated by plastic flow, or they may form additional voids by the mechanisms already discussed. The reaction sequence at the various interfaces (Fig. 1.87b) for the oxidation of iron (prior to the formation of Fe Oj) would be... 

The Space Shuttle uses aluminum metal and ammonium perchlorate in its reusable booster rockets. The products of die reaction are aluminum oxide, aluminum chloride, nitrogen oxide gas, and steam. The reaction mixture contains 7.00 g of aluminum and 9.32 g of ammonium perchlorate. 

When ammonia reacts with oxygen, nitrogen oxide gas and steam are formed. How much heat is evolved or absorbed when one liter of ammonia gas at 23.0°C and at 765 mm Hg reacts ... 

When ammonia reacts with dinitrogen oxide gas (AH = 82.05 kj/mol), liquid water and nitrogen gas are formed. How much heat is liberated or absorbed by the reaction that produces 345 mL of nitrogen gas at 25°C and 717 mm Hg ... 

At a certain temperature, nitrogen and oxygen gases combine to form nitrogen oxide gas. 

Cupric sulfide, copper(II) sulfide, reacts with hot nitric acid to produce nitric oxide gas, NO, and elemental sulfur. Only the oxidation numbers of S and N change. Write the balanced equation for the reaction. 

The total consumption type of burner consists of three concentric tubes as shown in Fig. 21.5. The sample solution is carried by a fine capillary tube A directly into the flame. The fuel gas and the oxidant gas are carried along separate tubes so that they only mix at the tip of the burner. Since all the liquid sample which is aspirated by the capillary tube reaches the flame, it would appear that this type of burner should be more efficient that the pre-mix type of burner. However, the total consumption burner gives a flame of relatively short path length, and hence such burners are predominantly used for flame emission studies. This type of burner has the advantages that (1) it is simple to manufacture, (2) it allows a totally representative sample to reach the flame, and (3) it is free from explosion hazards arising from unbumt gas mixtures. Its disadvantages are that (1) the aspiration rate varies with different solvents, and (2) there is a tendency for incrustations to form at the tip of the burner which can lead to variations in the signal recorded. 

A burner which utilises a mixture of fuel and oxidant gases and which is attached to a waste vessel (liquid trap) should be provided with a U-shaped connection between the trap and the burner chamber. The head of liquid in the connecting tube should be greater than the operating pressure of the burner if this is not achieved, mixtures of fuel and oxidant gas may be vented to the atmosphere and form an explosive mixture. The trap should be made of a material that will not shatter in the event of an explosive flash-back in the burner chamber. 

For food and pharmaceutical applications, the microbial count must be reduced to less than 10,000 viable cells per g exopolysaccharide. Treatment with propylene oxide gas has been used for reducing the number of viable cells in xanthan powders. The patented process involves propylene oxide treatment for 3 h in a tumbling reactor. There is an initial evacuation step before propylene oxide exposure. After treatment, evacuation and tumbling are alternated and if necessary the reactor is flushed with sterile nitrogen gas to reduce the residual propylene oxide level below the Food and Drug Administration permitted maximum (300 mg kg 1). The treated polysaccharide is then packaged aseptically. 

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