Oxygen mixture

Clock-type induction periods occur in the spontaneous ignition of hydrocarbon-oxygen mixtures [2], in the setting of concrete and the curing of polymers [3]. A related phenomenon is the induction period exhibited... 

Reference to Figure 3.4 shows that the reduction is not feasible at 800 K. but is feasible at 1300 K. However, we must remember that energetic feasibility does not necessarily mean a reaction will go kinetic stability must also be considered. Several metals are indeed extracted by reduction with carbon, but in some cases the reduction is brought about by carbon monoxide formed when air, or air-oxygen mixtures, are blown into the furnace. Carbon monoxide is the most effective reducing agent below about 980 K, and carbon is most effective above this temperature. 

The low breathing resistance of helium—oxygen mixtures is of therapeutic advantage for patients suffering from asthma and other obstmctive respitatory difficulties. The mixtures have also been used for hyperbaric therapy. 

Cool Flames. An intriguing phenomenon known as "cool" flames or oscillations appears to be intimately associated with NTC relationships. A cool flame occurs in static systems at certain compositions of hydrocarbon and oxygen mixtures over certain ranges of temperature and pressure. After an induction period of a few minutes, a pale blue flame may propagate slowly outward from the center of the reaction vessel. Depending on conditions, several such flames may be seen in succession. As many as five have been reported for propane (75) and for methyl ethyl ketone (76) six have been reported for butane (77). As many as 10 cool flames have been reported for some alkanes (60). The relationships of cool flames to other VPO domains are depicted in Figure 6. 

Montecatini Process. This partial combustion process operates at higher pressure, 405—608 kPa (4—6 atm), than the BASF and SBA processes. The burner dimensions are proportionately smaller. Because of the higher pressure, the danger of premature ignition of the methane—oxygen mixture is higher so that 2 vol % of steam is added to the gas mixture to alter the flammabiUty limits. 

In the heating and cracking phase, preheated hydrocarbons leaving the atomizer are intimately contacted with the steam-preheated oxygen mixture. The atomized hydrocarbon is heated and vaporized by back radiation from the flame front and the reactor walls. Some cracking to carbon, methane, and hydrocarbon radicals occurs during this brief phase. 

The calculated half-life of 1 mol % (1.5 wt %) of pure gaseous ozone diluted with oxygen at 25, 100, and 250°C (based on rate constants from Ref. 19) is 19.3 yr, 5.2 h, and 0.1 s, respectively. Although pure ozone—oxygen mixtures are stable at ordinary temperatures ia the absence of catalysts and light, ozone produced on an iadustrial scale by silent discharge is less stable due to the presence of impurities however, ozone produced from oxygen is more stable than that from air. At 20°C, 1 mol % ozone produced from air is - 30% decomposed ia 12 h. 

Nitrous oxide produces respiratory depression (38,39). It has been shown to produce a direct myocardial depressant effect in dogs (40) and in humans breathing a 40% N2O/60% oxygen mixture (41) however, this may be offset by the activation of the sympathetic nervous system (42). The combination of nitrous oxide and opioids can produce decreases in myocardial contractiHty, heart rate, and blood pressure (43). 

Flammability Limits There are both upper (or rich) and lower (or lean) limits of flammability of fuel-air or fuel-oxygen mixtures. Outside these hmits, a self-sustaining flame cannot form. Flammability limits for common fuels are listea in Table 27-18. 

TABLE 7.8 Explosive Limits of Some Gases in Air and Oxygen Mixtures ... 

Experimental data are available for detonation limits for a limited number of fuel-air and fuel-oxygen mixtures at atmospheric pressure in both confined and nnconfined situations. These are presented in Table 4-4 (Nettleton 1987). 

Free radicals can also be formed on the cellulose molecule by using H2O2 [20-23], ozone-oxygen mixture [21,22], perminganate [22], and bromate [24]. 

Figure 7-42A. Detonation velocities for hydrogen/oxygen mixtures. Note detonation range compared to flammability range of 4% to 95%. By permission. Ref. [41]., Stuii, The Dow Chemical Co. and The American Institute of Chemical Engineers Monograph No. 10, Vol. 73 (1977).

Figure 7-53. Detonation velocity, V, static pressure, Pg, and reflected pressure, Pp developed by detonation wave propagating through hydrogen-oxygen mixtures in a cylindrical tube at atmospheric pressure at 18°C. By permission, U.S. Bureau of Mines, Bulletin 627 [43].

Another consequence of the effect of pressure on gas solubility is the painful, sometimes fatal, affliction known as the bends. This occurs when a person goes rapidly from deep water (high pressure) to the surface (lower pressure), where gases are less soluble. The rapid decompression causes air, dissolved in blood and other body fluids, to bubble out of solution. These bubbles impair blood circulation and affect nerve impulses. To minimize these effects, deep-sea divers and aquanauts breathe a helium-oxygen mixture rather than compressed air (nitrogen-oxygen). Helium is only about one-third as soluble as nitrogen, and hence much less gas comes out of solution on decompression. 

Consider the combination of nitric oxide and oxygen. Nitric oxide (a colorless gas) when mixed with oxygen gas (also colorless) becomes reddish-brown. The color is identical to that of another gas, nitrogen dioxide. All the properties of the nitric oxide-oxygen mixture are consistent with the conclusion that the gas nitrogen dioxide has... 

Powder-Oxygen Mixtures , AIAAJournal 6, 1753 (1968) 10) K.N. Palmer PS. Tonkin,... 

An anesthetic gas, cyclopropane has a rapid onset of action and may be used for induction and maintenance of anesthesia Skeletal muscle relaxation is produced with full anesthetic doses. Cyclopropane is supplied in orange cylinders. Disadvantages of cyclopropane are difficulty in detecting the planes of anesthesia, occasional laryngospasm, cardiac arrhythmias, and postanesthesia nausea, vomiting, and headache Cyclopropane and oxygen mixtures are explosive, which limits the use of this gas anesthetic. 

The catalyst (spheres or rings with a diameter of 3-10 mm) contains 7-20% silver on high-purity a-AI203 having a surface of only <2 m2/g. Cesium or another alkali or earth alkali salt is added in an amount of 100-500 mg/kg catalyst for upgrading the selectivity. However, small amounts of halogen compounds, e.g., dichloroethane, are added to the ethylene/oxygen mixture to inhibit the total oxidation of the ethylene. 

Kuznetsov, M., Alekseev, V., Matsukov, L, and Dorofeev, S., DDT in a smooth tube filled with a hydrogen-oxygen mixture. Shock Waves, 14, 205-215, 2005. 

Gardner, W.E. and Pugh, A., The propagation of flame in hydrogen-oxygen mixtures, Trans. Faraday Soc., 35 283, 1939. 

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