Inert gas/-atmosphere

Solvent (reaction medium) In most of the cases, solvent is selected with high boiling point (or) with low vapor pressure in order to generate effective cavitation. Gas atmosphere Inert gases like Ar is used in general as cavitation is favored in this atm. 

The process of dissolution of a solid in a liquid can readily be investigated using a rapid-quenching device like that shown schematically in Fig. 5.3. Depending on the nature of substances to be studied, this may be carried out either in vacuum, or in a protective atmosphere (inert gases, hydrogen, nitrogen, etc), or under a flux.197,303309... 

The physiological and biochemical effects of the atmospheric inert gases should not be excluded from consideration in high pressure physiology studies. 

Emission into the atmosphere Inert gases that do not pollute the environment, like N2. O2. noble gases ... 

For the preparation in glass, the double-tube arrangement shown in Fig. Id is used, and an excess of 5% sodium is used to counterbalance the reaction of sodium with the glass wall. After sealing this inner ampule under atmospheric inert-gas pressure, it is rigorously shaken to provide an intimate mixture of P and Na. The inner ampule serves as reaction ampule, thus preventing the corrosion of the outer ampule. The outer ampule is also sealed under atmospheric pressure, in order to counterbalance the vapor pressure of phosphorus ( 10 atm at 500°). Typical batch sizes are a maximum of 4.5 g Na (19.6 mmol) and 13.45 g (43.5 mmol) in an inner reaction ampule (15 mm diameter, 20 cm in length). To facilitate the kinetically hindered vaporization of phosphorus, a trace of iodine or sulfur is added directly in the reaction ampule. 

Vapor Treatment. The vapors from the tank space can be sent to a treatment system (condenser, absorption, etc.) before venting. The system shown in Fig. 9.1 uses a vacuum-pressure relief valve which allows air in from the atmosphere when the liquid level falls (Fig. 9.1a) but forces the vapor through a treatment system when the tank is filled (Fig. 9.16). If inert gas blanketing is required, because of the flammable nature of the material, then a similar system can be adopted which draws inert gas rather than air when the liquid level falls. 

This eliminates the vapor space but sealing the edge can be a problem. Double seals can help and sometimes a fixed roof is also added above the floating roof to help capture any leaks from the seal. However in this case, the space between the fixed and floating roof now breathes and an inert gas purge of this space would typically be used. The inert gas would be vented to atmosphere after treatment. 

II, 36, 1 is almost self explanatory two ground glass joints are used, but these may be replaced by rubber stoppers, if desired. The crude substance is placed in the flask A. Stopcocks 1 and 2 are closed, and the apparatus is exhausted through tap 3 the indifferent gas is then allowed to enter the apparatus to atmospheric pressure. The evacuation and filling with inert gas are repeated several times. The solvent is added through the tap funnel B. 

Metallui ical. To prevent reaction with atmospheric oxygen and nitrogen, some metals must be shielded using an inert gas when heated or melted (94). AppHcations in metals processing account for most argon consumption and an important part of helium usage (see AfETALLURGY). 

The narcotic potency and solubiUty in oHve oil of several metabohcaHy inert gases are Hsted in Table 10. The narcotic potency, ED q, is expressed as the partial pressure of the gas in breathing mixtures requited to produce a certain degree of anesthesia in 50% of the test animals. The solubiUties are expressed as Bunsen coefficients, the volume of atmospheric pressure gas dissolved by an equal volume of Hquid. The Hpid solubiHty of xenon is about the same as that of nitrous oxide, a commonly used light anesthetic, and its narcotic potency is also about the same. As an anesthetic, xenon has the virtues of reasonable potency, nonflammability, chemical inertness, and easy elimination by the body, but its scarcity and great cost preclude its wide use for this purpose (see Anesthetics). 

Sihcon nitride can be heated ia air up to 1450—1550°C. In nitrogen, inert gas, or reducing atmosphere, Si N can be heated up to 1750°C. Above 1750°C, decomposition and sublimating evaporation become severe. When in the presence of carbon, however, Si N stabiUty depends on temperature and pressure. The equiUbrium temperature for the reaction... 

In plasma chromatography, molecular ions of the heavy organic material to be analy2ed are produced in an ionizer and pass by means of a shutter electrode into a drift region. The velocity of drift through an inert gas at approximately 101 kPa (1 atm) under the influence of an appHed electric field depends on the molecular weight of the sample. The various sonic species are separated and collected every few milliseconds on an electrode. The technique has been employed for studying upper atmosphere ion molecule reactions and for chemical analysis (100). 

Rotomolding. Nylon-6, nylon-11, and nylon-12 can be used in rotomolding and are generally suppHed for these appHcations as a powder or with a small pellet si2e. The process involves tumbling the resin in a heated mold to form large, thin-walled mol dings. Nylon-11 and nylon-12 use mold temperatures of 230—280°C and nylon-6 is processed at over 300°C. An inert gas atmosphere is preferred to avoid oxidation. 

Gas-flow counting is a method for detecting and quantitating radioisotopes on paper chromatography strips and thin-layer plates. Emissions are measured by interaction with an electrified wire in an inert gas atmosphere. AH isotopes are detectable however, tritium is detected at very low (- 1%) efficiency. 

For quantitative analysis, the resolution of the spectral analyzer must be significantly narrower than the absorption lines, which are - 0.002 nm at 400 nm for Af = 50 amu at 2500°C (eq. 4). This is unachievable with most spectrophotometers. Instead, narrow-line sources specific for each element are employed. These are usually hoUow-cathode lamps, in which a cylindrical cathode composed of (or lined with) the element of interest is bombarded with inert gas cations produced in a discharge. Atoms sputtered from the cathode are excited by coUisions in the lamp atmosphere and then decay, emitting very narrow characteristic lines. More recendy semiconductor diode arrays have been used for AAS (168) (see Semiconductors). 

Internal pressure may be caused by several potential sources. One source is the vapor pressure of the Hquid itself. AH Hquids exert a characteristic vapor pressure which varies with temperature. As the temperature iacreases, the vapor pressure iacreases. Liquids that have a vapor pressure equal to atmospheric pressure boH. Another source of internal pressure is the presence of an iaert gas blanketing system. Inert gas blankets are used to pressuri2e the vapor space of a tank to perform speciali2ed functions, such as to keep oxygen out of reactive Hquids. The internal pressure is regulated by PV valves or regulators. 

TJItrahigh (99.999 + %) purity tellurium is prepared by zone refining in a hydrogen or inert-gas atmosphere. Single crystals of tellurium, tellurium alloys, and metal teUurides are grown by the Bridgman and Czochralski methods (see Semiconductors). 

Reduction. BrezeHus attempted the first reduction of zirconium in 1824 by the reaction of sodium with potassium fiuorozirconate. However, the first pure ductile metal was made in 1925 by the iodide thermal-dissociation method. The successfiil commercial production of pure ductile zirconium via the magnesium reduction of zirconium tetrachloride vapor in an inert gas atmosphere was the result of the intense research efforts of KroU and... 

Mixing cellulose esters in nonpolar hydrocarbons, such as toluene or xylene, may result in static electricity buildup that can cause a flash fire or explosion. When adding cellulose esters to any flammable Hquid, an inert gas atmosphere should be maintained within the vessel (132). This risk may be reduced by the use of conductive solvents in combination with the hydrocarbon or by use of an antistatic additive. Protective clothing and devices should be provided. 

Storage. Purified and dry aHyl chloride can be safely stored in carbon steel vessels. Use of lined vessels is recommended if slight discoloration or trace presence of metals is undesirable for its intended use. In any event, the presence of air should be avoided for safety (flammabHity) reasons through the use of an inert gas pad. Tank vents should be treated, eg, by incineration, prior to venting to the atmosphere. Some commercial producers intentionaHy add about 0.1% propylene oxide as a stabilizer to prevent discoloration however, this is usuaHy unnecessary if product purity is sufficiently high. 

Another purpose of inerting is to control oxygen concentrations where process materials are subject to peroxide formation or oxidation to form unstable compounds (acetylides, etc.) or where materials in the process are degraded by atmospheric oxygen. An inert gas supply of sufficient capacity must be ensured. The supply pressure must be monitored continuously. 

Provide automatic sprinkler system/inerting gas Provide deflagration vents Provide deflagration suppression system Monitor flammable atmosphere/fire Provide nitrogen blocks (nitrogen injection to stop flame propagation) or other explosion isolation measures... 

Inert gas not present leading to creation of flammable atmosphere. 

Some stabilizers or inhibitors require a certain oxygen concentration in the tank head space atmosphere in order to function. Where inerting is required, careful control is necessary to maintain this minimum oxygen concentration in inerting gas while still staying below the minimum oxygen concentration required for combustion. 

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