Oxide vaporization

White Phosphorus Oxidation. Emission of green light from the oxidation of elemental white phosphoms in moist air is one of the oldest recorded examples of chemiluminescence. Although the chemiluminescence is normally observed from sotid phosphoms, the reaction actually occurs primarily just above the surface with gas-phase phosphoms vapor. The reaction mechanism is not known, but careful spectral analyses of the reaction with water and deuterium oxide vapors indicate that the primary emitting species in the visible spectmm are excited states of (PO)2 and HPO or DPO. Ultraviolet emission from excited PO is also detected (196). 

Table 3. Physical Properties of Ethylene Oxide Vapor from 298 to 800 K...

Miscellaneous Reactions. Ethylene oxide is considered an environmental pollutant. A study has determined the half-life of ethylene oxide ia the atmosphere (82,83). Autodecomposition of ethylene oxide vapor occurs at - 500° C at 101.3 kPa (1 atm) to give methane, carbon monoxide, hydrogen, and ethane (84—86). 

The third key section of the process deals with ethylene oxide purification. In this section of the process, a variety of column sequences have been practiced. The scheme shown in Figure 2 is typical. The ethylene oxide-rich water streams from both the main and purge absorbers are combined, and after heat exchange are fed to the top section of a desorber where the absorbate is steam stripped. The lean water from the lower section of the desorber is virtually free of oxide, and is recirculated to the main and purge absorbers. The concentrated ethylene oxide vapor overhead is fed to the ensuing stripper for further purification. If the desorber is operated under vacuum, a compressor is required. 

Ethylene oxide storage tanks ate pressurized with inert gas to keep the vapor space in a nonexplosive region and prevent the potential for decomposition of the ethylene oxide vapor. The total pressure that should be maintained in a storage tank increases with Hquid temperature, since the partial pressure of ethylene oxide will also increase. Figure 5 shows the recommended minimum storage pressures for Hquid ethylene oxide under nitrogen or methane blanketing gas. 

While the deflagration pressure ratio for ethylene oxide vapor is about 11 or less, Hquid mist decomposition can give much greater pressures and very fast rates of pressure rise (190). 

Explosion prevention can be practiced by mixing decomposable gases with inert diluents. For example, acetylene can oe made nonexplosive at a pressure of 100 atm (10.1 MPa) by including 14.5 percent water vapor and 8 percent butane (Bodurtha, 1980). One way to prevent the decomposition reaction of ethylene oxide vapor is to use methane gas to blanket the ethylene oxide hquid. 

Many accidents occur because process materials flow in the wrong direction. Eor example, ethylene oxide and ammonia were reacted to make ethanolamine. Some ammonia flowed from the reactor in the opposite direction, along the ethylene oxide transfer line into the ethylene oxide tank, past several non-return valves and a positive displacement pump. It got past the pump through the relief valve, which discharged into the pump suction line. The ammonia reacted with 30m of ethylene oxide in the tank, which ruptured violently. The released ethylene oxide vapor exploded causing damage and destruction over a wide area [5]. A hazard and operability study might have disclosed the fact that reverse flow could occur. 

It has been reported that exchange of protons activated by enolization can be performed directly in a glass inlet system of the mass spectrometer prior to analysis by heating the sample at about 200° with deuterium oxide vapor for a few minutes. " Exchange has been observed with 2-, 3-, 6-, 11- and 17-keto steroids, but the resulting isotopic purity is usually poor,... 

Thibault, P., Britton, L. G., and Zhang, F. 2000. Deflagration and Detonation of Ethylene Oxide Vapors m Pipelines. Process Safety Progress, 19(3), 125-139. an Dolah, R. W. and Burgess, D. S. 1974. Explosion Problems in the Chemical Industry. 

The continuous sintering is mainly a zone sintering process in which the electrolyte tube is passed rapidly through the hot zone at about 1700 °C. This hot zone is small (about 60 mm) in zone sintering, no encapsulation devices are employed. The sodium oxide vapor pressure in the furnace is apparently controlled by the tubes themselves. Due to the short residence time in the hot zone, the problem of soda loss on evaporation can be circumvented. A detailed description of / "-alumina sintering is given by Duncan et al. [22]. 

Thermodynamic Functions of the Gases. To apply Eqs. (1-10), the free energies of formation, Ag , for all gaseous species as a function of temperature are required. Tabulated data were fit by a least-squares procedure to derive an analytical equation for AG° of each vapor species. For the plutonium oxide vapor species, the data calculated from spectroscopic data (3 ) were used for 0(g) and 02(g), the JANAF data (.5) were used and for Pu(g), data from the compilation of Oetting et al. (6) were used. The coefficients of the equations for AG° of the gaseous species are included in Table I. 

Coefficients, distribution—See Distribution coefficients Coefficients of free energy of formation equation, Pu oxide vapor. 127/... 

Ethylene oxide reactions, 20 636, 637-640 Ethylene oxide vapor... 

Propylene oxide selectivity, 20 806-807 Propylene oxide vapors, 20 811 Propylene oxide-styrene (PO-SM)... 

Jacobson KH, Hackley EB, Eeinsilver L The toxicity of inhaled ethylene oxide and propylene oxide vapors. AMA Arch Ind Health 13 237-244, 1956... 

The compound is prepared in a retort attached to inlet tubes for dry chlorine and dry carbon dioxide and a distillation flask. White phosphorus is placed on sand in the retort. All air, moisture, and any phosphorus oxide vapors present in the apparatus are expelled by passing dry carbon dioxide. Dry chlorine is then introduced into the apparatus. If a flame appears on phosphorus it indicates presence of excess chlorine. In that event, the rate of chlorine introduction should be decreased. For obtaining phosphorus trichloride, flame should appear at the end of the chlorine-entry tube. The trichloride formed is collected by condensation in the distillation flask. A soda hme tube is attached to the apparatus to prevent moisture entering the flask. 

Any material proposed for implantation, whether for cell transplantation or some other application, must be biocompatible i.e. it must not provoke an adverse response from the host s immune system. If this goal is not met the implant may be rejected. To this end it is important that the material be easily sterilized either by exposure to high temperatures, ethylene oxide vapor, or gamma radiation. A suitable material must therefore remain unaffected by one of these three techniques. However, biocompatibility is not simply a question of sterility. The chemistry, structure, and physical form of a material are all important factors which determine its biocompatibility. Although our understanding of the human immune system is advancing rapidly, it is not yet possible to predict the immune response to a new material. This can only be determined by in vivo experiments. 

By controlling the structural and electronic properties of sNPS which are related to the nanocrystallite dimensions and porosity, their surface selectivity and sensitivity to different gases (nitrogen and carbon oxide, vapors of water and organic substances) can be adjusted. This approach for the effective detection of acetone, methanol and water vapor in air was described in [13-15].The minimal detectable acetone concentration was reported to be 12 pg/mL. Silicon sensors for detection of SO2 and some medicines such as penicillin were created [16-18]. sNPS were used for the development of a number of immune biosensors, particularly using the photoluminescence detection. Earlier we developed similar immune biosensors for the control of the myoglobin level in blood and for monitoring of bacterial proteins in air [19-23]. 

Explosibility. Liquid ethylene oxide is stable to detonating agents, but the vapor will undergo explosive decomposition. Pure ethylene oxide vapor will decompose partially however, a slight dilution with air or a small increase in initial pressure provides an ideal condition for complete decomposition. Copper or other acetylide-forming metals such as silver, magpesium, and alloys of such metals should not be used to handle or store ethylene oxide because of the danger of the possible presence of acetylene. Acetylides detonate readily and will initiate explosive decomposition of ethylene oxide vapor. In the presence of certain catalysts, liquid ethylene oxide forms a poly-condensate. 

Toxicity of EtnO (Ref 17, pp 314—15 Spec MIL-E-52171). Liquid EtnO, concentrated or dilute, when exposed to the skin can cause -severe delayed bums. Short exposures produce mild first degree bums, but prolonged exposures produce second degree bums with the formation of large blisters. Exposure to the vapor results in systemic manifestations and irritation to the respiratory system. Inhalation of ethylene oxide vapors, if. prolonged, results in severe systemic poisoning with the symptoms of nausea, vomiting, headache, dysnea, and diarthea. The anesthetic properties are similar to chloroform, but with pronounced undesirable side and after effects. 

Tests on gninea pigs have shown that a 5 percent by volume concentration of ethylene oxide vapor kills in a short time. The maximum concentration for 60 minutes without serious disturbance was 0.3 percent by volume. 

Above the decomposing surfaces of AP crystals and exposed solid fuel a diffusion flame exists, which represents the reaction between fuel and oxidant vapors. 

High Temperature Measurements of the Rates of Uptake of Molybdenum Oxide, Tellurium Oxide, and Rubidium Oxide Vapors by Selected Oxide Substrates... 

The rates of uptake of molybdenum, tellurium, and rubidium oxide vapors by substrates of calcium ferrite and a clay loam have been measured in air over a temperature range of 900° to 1500°C. and a partial pressure range of about 10r7 to 10 atm. The measured rates of uptake of molybdenum and tellurium oxide vapors by molten calcium ferrite and of rubidium oxide vapor by both molten clay loam and calcium ferrite were controlled by the rates of diffusion of the oxide vapors through the air. The measured rates of uptake of molybdenum and tellurium oxide vapors by molten clay loam were controlled by a combination of a slow surface reaction and slow diffusion of the condensate into the substrate. 

A dry air stream was introduced into the furnace via a hole in the small alumina tube just below the top alumina plug. The air flowed up and around the top alumina plug where it mixed with the radioactive oxide vapor, and the air-radioactive oxide vapor mixture flowed up through the high temperature zone and left through the top of the furnace. 

The interior of the furnace was lined with platinum foil to limit any reaction of the oxide vapors with the alumina furnace walls. Three perforated platinum foil diaphragms were placed at intervals inside the furnace to act as heat shields and to ensure thorough mixing of the oxide vapor-air mixtures. 

Preparation of Materials and Samples. The source of the molybdenum oxide vapor was M0O3 containing "Mo tracer. The "Mo was supplied as ammonium molybdate in NH4OH solution (Nuclear Science and Engineering Co.). The solution was evaporated to dryness in a platinum crucible, and the ammonium molybdate was heated in air at about 500°C. for several hours to decom ose it to M0O3. 

Procedure. In preparation for a series of experimental runs, the top and bottom sections of the furnace were brought to their proper operating temperatures, the air flow was started, and a standby source of radioactive oxide vapor was inserted into the lower section of the furnace. After about a 24-hour equilibration period, the standby oxide source was replaced with the regular source which had just been weighed. 

At the end of each day s runs, the regular radioactive vapor source was removed from the furnace and was replaced by the standby source. The regular source was then reweighed, and the amount of radioactive oxide vapor which had evaporated was determined. This weight, combined with the known volume of air passed through the furnace, gave the vapor concentration of the radioactive oxide in the furnace. 

Some checks on the experimental techniques were made. There was uncertainty as to whether or not the vapor concentrations in the furnace might not be changed by repeated opening of the furnace lid for the inserting and removing the samples. To test this effect, two identical samples of clay loam were prepared and were exposed to molybdenum oxide vapor in the furnace. One sample was inserted into the furnace and left for 60 minutes and then withdrawn and counted. The other sample was inserted and withdrawn 12 times. Each interval in the furnace was 5 minutes, and the sample was counted after a total accumulated time in the furnace of 60 minutes. It was found that the sample which had been left in the furnace for the one 60-minute interval had taken up 7% less M0O3 than the sample which had been exposed for 12 five-minute intervals. This discrepancy is considerably smaller than the over-all accuracy of the measurements, and therefore no correction was applied to the data. 

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