Addition Of Inert Gas Research Articles

Kinetics and mechanism of the explosive reaction of carbon monoxide and oxygen

AbstractA new technique is described for quantitative measurement of the conditions of reactant concentration at ignition in mixtures of carbon monoxide and oxygen. A thin film of carbon covering the surface of a quartz reaction vessel reacted with oxygen to form carbon monoxide and small quantities of water. Explosions were observed above 900 K over the pressure range 15–100 torr with ratios of CO/O2 far below those hitherto explored. The onset of explosion was favored by the addition of hydrogen, methane, and water and was inhibited by the addition of inert gases. A simple mechanism predicts the occurrence of an explosion over a wide range of product composition and total pressure.

The mass transport rate of mercuric iodide during its crystallization from the vapor phase

The mass transport rate of mercuric iodide has been measured as a function of source temperature and argon pressure in closed ampoules without any nucleation control. Two values of activation energy have been found: about 80 kJ mole -1 for sublimed and zone refined source material transported in the presence of argon and about 60 kJ mole -1 for sublimed only material transported without addition of inert gas. It has been concluded that the evaporation of the source was the rate determining step in the first case and that the 25% decrease in activation energy in the second case was caused by diffusion through the residual gases in the system. An apparent evaporation coefficient α′ evap of the order of 10 -3 has been also evaluated from the experimental data.

Thermal effects in infrared laser photochemistry and energy transfer experiments

Addition of nonabsorbing inert gas to a cell, in which laser pulses are absorbed by a second low pressure gas, is commonly believed to reduce the peak, axial, translational temperature rise due to the increased heat capacity of the system. It is shown that this interpretation is often incorrect and that the axial temperature rise, as a function of inert gas pressure, passes through a maximum as a consequence of the variation with pressure of the thermal diffusivity and V–T energy transfer relaxation time. In the case of experiments where the laser beam is focused into the cell, the dependence on wavelength of the focal cylinder diameter is shown to have a strong effect on the temperature of and thus on comparative results of experiments using common optical systems at different wavelengths. Results of thermal lens experiments are used to support these conclusions and representative IR laser photochemical data are reassessed, conclusions on ’’hole burning’’ in populations of specific levels being shown to be of doubtful validity.

Rotational effects in multiphoton excitation of hot molecules

The visible chemiluminescence resulting from infrared multiphoton excitation (MPE) of CrO2Cl2 is used to study the effect of inert gas addition on the yield and branching ratio of MPE induced reactions. In some cases, addition of foreign gases increases the chemiluminescence yield, and also leads to a blue shift in the emission spectrum. This result may indicate bottleneck formation in the quasicontinuum region. This bottlenecking is discussed using a model that calls for a gradual broadening of single rotational lines as energy is accumulated in the molecule. Under appropriate conditions, fast rotational relaxation can lead to higher average vibrational energy, as well as to a significant population increase in the high energy tail of the vibrational distribution. A stochastic method is used to solve the rate equations. This computationally simple technique is particularly useful in the limiting case of fast rotational relaxation.

Deodorization and finished oil handling

AbstractDeodorization is the final processing step in the production of edible oil products. Chemical/physical aspects of deodorization and mechanical design of deodorizers are explained, including chemical analysis of feedstock, finished product and by‐products. This includes normal operating standards and means of correcting off specification operation. Operating procedures, labor requirements and maintenance are reviewed. Finished oil handling includes use of antioxidants, inert gas addition, pipelines and storage facilities. Emphasis is on the practical operations of deodorization and finished soybean oil handling.

Photofragment fluorescence polarization following photolysis of HgBr2 at 193 nm

When HgBr2 (2–45 mTorr) is photolyzed by the linearly polarized output of an ArF excimer laser (193 nm), the visible emission from the HgBr B 2Σ+ fragment is found to be linearly polarized. The degree of polarization is 11.9%±1.5%, in close agreement with the theoretical value of 14.3% predicted for a 1Σg+(1A1) →1B2(1Σu+) dissociative transition in HgBr2. The addition of inert gases depolarizes the HgBr* emission. A simple model, developed to calculate the average angle through which the angular momentum vector of the HgBr* fragment is tipped by each hard sphere collision, fits well the pressure dependence of the depolarization.

Infrared photodissociation of fluorinated ethanes and ethylenes: Collisional effects in the multiple photon absorption process

The ir photodissociation of fluorinated ethanes and ethylenes produces vibrationally excited HF via collisionless molecular elimination. Monitoring of the time resolved HF fluorescence is used as a probe to examine the effects that collisions with inert gas molecules have on the ir photodissociation process. The addition of inert gas is shown to enhance the dissociation yield. Mechanisms which may be responsible for this enhancement are discussed. An example of consecutive dissociation events within the same laser pulse is presented. The energy absorbed in excess of the minimum required for dissociation, the absorption cross section, and the energy absorption rate of highly vibrationally excited vinyl fluoride are estimated.

Improvement of Oscillation Characteristics in He-Zn Hollow Cathode Laser by the Addition of Inert Gas and its Mechanisms

Improvement of Oscillation Characteristics in He-Zn Hollow Cathode Laser by the Addition of Inert Gas and its Mechanisms

Computerized electroanalysis: Part I. Instrumentation and programming

The electronic circuit of a computerized electroanalytical instrument is described. The computer is programmed in a high-level language. The instrument can generate linear potential scans of any conceivable form within a wide range of scan rates. Pulses of varying height and duration can be superimposed on the linear scans. Stirrer motors, inert gas flow and addition of standard reagent are under computer control, thus permitting completely automatic analytical procedures. Data are displayed on a graphical screen. Results from anodic stripping experiments are given.

Yield optimisation of a condensed product by addition of inert gas

Yield optimisation of a condensed product by addition of inert gas

ChemInform Abstract: PHOTODISSOCIATION OF GASEOUS OLEFINIC CATIONS

Chemischer InformationsdienstVolume 5, Issue 3 Physical Organic Chemistry ChemInform Abstract: PHOTODISSOCIATION OF GASEOUS OLEFINIC CATIONS JERRY M. KRAMER, JERRY M. KRAMERSearch for more papers by this authorROBERT C. DUNBAR, ROBERT C. DUNBARSearch for more papers by this author JERRY M. KRAMER, JERRY M. KRAMERSearch for more papers by this authorROBERT C. DUNBAR, ROBERT C. DUNBARSearch for more papers by this author First published: January 22, 1974 https://doi.org/10.1002/chin.197403078AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume5, Issue3January 22, 1974 RelatedInformation

The role of excited states in the gas-phase photolysis of acetaldehyde

The cis-trans isomerization of butene-2 has been used to measure the triplet state yields in the photolysis of acetaldehyde at various wavelengths between 313 and 254 nm over the temperature range 35 to 140 °C. The results, together with those derived from chemical product formation, are consistent with data from luminescence studies. Dissociation into molecular products occurs rapidly, probably by predissociation, from a non-quenchable excited state formed by absorption. The main free radical decomposition occurs from the triplet state and this, in the absence of additives, such as butene-2, is responsible for the chain decomposition. The intersystem crossing and non-quenchable processes are independent of temperature. Isopentyl radicals formed from methyl addition to butene-2 can also propagate a chain reaction for acetaldehyde decomposition. At high temperatures and low pressures, dissociation of vibrationally excited isopentyl radicals can contribute to the measured isomerization yield. This is shown by the effect of addition of inert gas. Evidence is put forward that geometrical isomerization of the olefin involves a triplet aldehyde-olefin complex that can be decomposed by collision with ground state aldehyde molecules without cis-trans rearrangement of the olefin. This conclusion is consistent with other work in the gas and liquid phases.

Photodissociation of gaseous olefinic cations

An ion cyclotron resonance spectrometer was used to study the wavelength dependence of the photodissociation of cations in propene and several isomeric butenes. Photodissociation onsets were determined and compared with electron impact and thermodynamic values. In all cases the photodissociation onsets were found to be above both the thermodynamic onset and the first excited state of the cation as determined by photoelectron spectroscopy. The onset results were compatible with a photodissociation mechanism that proceeds by initial excitation into the first excited state, followed by dissociation. A large increase in the photodissociation cross section for all the cations studied was observed at [inverted lazy s] 3.7 eV. This increase correlated with the second excited states of all the cations except 1-butene. Internal excitation of the parent cations was investigated by the addition of inert gas and by changing the electron beam energy. Photodissociation onsets were also found to be valuable in choosing between alternative structures for gas-phase cations. At least two noninterconverting isomers of C4H8+ were shown to exist.

Laser emission from CO formed in the flash-initiated reactions of O(3 P) atoms with CS and CSe

A study has been made of the laser emission from vibrationally excited CO (CO) formed in the reactions: O(3P)+ CS → CO + S + 356 kJ mol–1(1) and O(3P)+ CSe → CO + Se +∼494 kJ mol–1, (5), with O atoms being produced directly by flash photolysis of SO2. Comparison of the emission from CS2+ SO2 with that from CS2+ O2 established (a) that excitation and quenching of SO2 can lead to appreciable heating and as a result lower gains, and (b) that relaxation of CS†, before it reacts, by SO2 and free S atoms modifies the laser output significantly. The rise in temperature can be moderated by addition of inert gas or SF6, but the latter must be used with care as it also relaxes the higher levels of CO† efficiently. Oscillation has been observed on all vibrational transitions from (20, 19) to (9, 8) with mixtures containing CSe2 and SO2; the delay times before individual transitions appeared are consistent with the CO vibrational distribution predicted from infra-red chemiluminescence experiments. The absence of lower transitions is probably due to relaxation in the processes CO(v)+ Se(3P2)→ CO(v– 1)+ Se(3P1)(7) which are close to resonance when v∼7.

PAДИAЦИOHHO-XИMИЧECКAЯ ФИКCAЦИЯ MOЛEКyЛЯPHOГO AЗOTA

The action of 340 kV electrons or γ- 60Co on gaseous mixtures of molecular nitrogen with various hydrocarbons give rise to radiation fixation of nitrogen. In all cases hydrocyanic acid is the main low molecular weight product of fixation. The radiation-chemical yield G(HCN) depends on the nature of the hydrocarbon and the ratio of components. the maximum G(HCN) values are obtained when the nitrogen/hydrocarbon ratio is 10:90. Most of the present experiments were carried out under an absolute pressure of 2 atm (200 kN m −2). The addition of inert gases to the mixtures increases G(HCN), which is 1⋅ for a mixture of 5 per cent CH 4, 5 per cent N 2 and 90 per cent Ar. Replacing nitrogen by air in the mixtures containing methane leads to a practically complete inhibition of HCN production due to interaction of methyl radicals and oxygen manifests the opposite effect in the case of mixtures of nitrogen with unsaturated hydrocarbons. Foe ethylene the maximum G(HCN) increases from 0⋅27 for ethylene-nitrogen mixtures to 0⋅48 for mixtures of ethylene and air. G(HCN) increases from 0c⋅23 to 1c⋅16 when passing from acetylene-nitrogen mixtures to acetylene-air mixtures; nitrogen-containing cuprene is not formed in the presence of oxygen. To elucidate a possible role of reactions of the methylene radical and atomic nitrogen, HCN synthesis in ketene-nitrogen mixtures has been studied. A maximum of G(HCN) = 1⋅6 is reached with 10 per cent of ketene. The addition of oxygen to the mixtures just slightly reduces G(HCN). The addition of small concentrations of N 2O to the mixtures of ethylene and nitrogen has the usual inhibition action. But when using N 2O as a nitrogen-containing component in the mixtures with ethylene, the maximum G(HCN) is three times larger that from C 2H 4−N 2 mixtures. It is 1⋅6 times smaller when replacing nitrogen by nitrous oxide in the mixtures with methane. Ammonia is also formed in hydrocarbon-nitrogen mixtures; G(NH 3) is comparable to G(HCN) for N 2−CH 4 mixtures. Acetonitrile ( G=0⋅6) and acrylonitrile ( G≈0⋅03) have been identified in CH 4N 2 mixtures irradiate under high pressures (50–75 atm = 5−7⋅5 MN m -2). Nitrogen-containing cuprene producedin C 2H 2–N 2 mixtures with high yield ( G ≈ 5) is more thermostable than usual cuprene and probably contains nitrogen in the form of various functional groups.

Hydrogen Formation in the Photolysis of Propyne at 1236 Å

Hydrogen formation in the photolysis of propyne at 1236 Å occurs exclusively via a molecular process. The following reactions are energetically possible at 1236 Å: CH3C≡CH + hν → C3H2 + H2→ C3H+H+H2→ C3+2H2→ CH+C2H+H2.Photolysis of CH3C≡CH yields equal amounts of D2 and HD; addition of inert gas (C2F6) reduces HD relative to D2. These observations are taken as evidence for participation of the over-all Process (E) which may be rewritten as follows: CH3C≡CH + hν → C3HD* + D2,C3DH* → C3 + HD,C3DH* + M → C3DH + M.The dissociative lifetime of C3DH* is estimated to be 10−10 sec assuming unit efficiency for collisional deactivation.

Pressure effects and quantum yields in the photolysis of ethylene and propene at 185 nm

Gaseous ethylene and propene were photolysed with varying amounts of added nitrogen, oxygen, and other gases. The product analysis and variation of yields with added gas are consistent with the major primary reactions (i)–(v) for which the primary quantum yields were estimated. Several other minor primary reactions were found. The C2H4+hν(λ= 185 nm)→ C2H2+ H2; ϕ= 0·68 (i), → C2H2+ 2H; ϕ= 0·20 (ii), → C2H3+ H; ϕ= 0·16 (iii), C3H6+hν(λ= 185 nm)→ CH2:CHCH2·+ H; ϕ= 0·41 (iv), → C2H3·+ CH3; ϕ= 0·36 (v) reactions are inhibited by the addition of inert gases ranging from He to CO2; the inhibition is, within experimental error, the same for each additive. Higher pressures were needed to inhibit the ethylene photolysis than other olefins studied and the effect is attributed to the smaller collision diameter of the excited state in ethylene. The results for propene can be explained by a mechanism involving two excited intermediates, only one of which is readily quenched.

Collisional deactivation of singlet methylene in the photolysis of ketene

An investigation has been made into the effect of inert gas additions on product quantum yields for the photolysis at 2800 and 2490 Å of mixtures of ketene and oxygen and for the photolysis at 2800 Å of mixtures of ketene and carbon monoxide. Concentration ratios of O2 (or CO) to CH2CO were chosen so that the reaction of CH2(3Σg−) with CH2CO could be ignored and C2H4 formation could be attributed entirely to the reaction[Formula: see text]Quenching of the C2H4 quantum yield by inert gases was interpreted in terms of collisional deactivation of CH2(1A1) to the ground state[Formula: see text]and rate constant ratios k2/k1 have been determined for a number of gases: He (0.018), Ar (0.014), Kr (0.033), Xe (0.074), N2 (0.052), N2O (0.10), CF4 (0.047), C2F6 (0.11), and SF6 (0.045). It has been assumed that collision-induced intersystem crossover in excited singlet ketene makes an insignificant contribution to the observed quenching effects, but it has not been possible to verify this assumption experimentally. The mechanism of collision-induced electronic relaxation of singlet methylene is discussed in the light of the results.

The cool flame combustion of ethanol

The kinetics and products of the cool flame combustion of ethanol between about 280 and 330°C have been studied using a static system. The oxidation exhibited a long induction period, during which very little reaction occurred, followed by a period during which the rate, as measured by temperature and pressure increase and by consumption of reactants, accelerated exponentially. The passage of a cool flame was marked by a sharp increase in rate. During the acceleration period before a flame, the main products were hydrogen peroxide, water, carbon oxides, acetaldehyde, formaldehyde and methanol, the concentrations of which increased continuously except for acetaldehyde which rose to a constant value or even a maximum. Added acetaldehyde did not completely remove the induction period and did not reduce the acceleration period unless the amount added was greater than that normally present just before a cool flame passed. Coating the vessel with potassium chloride markedly inhibited cool flame formation. The temperature rise in a mixture up to the passage of a cool flame (∆ T c. f. ) was found to be constant at a constant ambient temperature ( T 0 ) on varying the mixture composition and total pressure and on addition of inert gases, but probably increased slightly with increasing T 0 . When only slow oxidation occurred the maximum temperature rise was less than Δ T c. f. . In contrast, the amount of alcohol consumed up to the cool flame was much less for a 1:2 than for a 1:1 ethanol/oxygen mixture at constant T 0 and varied with total pressure and on addition of inert gases. Addition of He, CO 2 and H 2 O increased the cool flame pressure limit at constant T 0 , whereas Ar and Xe reduced it. The results indicate that branching was probably due to the decomposition of an acetyldehyde-hydrogen peroxide compound and that thermal factors, particularly the thermal conductivity of the mixture, were of predominant importance in determining whether a cool flame occurred. The variation in the consumption of ethanol up to the cool flame with conditions has been explained qualitatively by considering the oxidation simply as a self-heating reaction. The sudden increase in rate when a cool flame occurred may have been due to spontaneous ignition of a peroxidic intermediate.

Photolysis of isobutene at 185 nm

On photolysis at 185 nm in a mercury-free system, isobutene, 2-methyl propene, yields hydrogen. thirty-one hydrocarbon products and a solid polymer (table 1). The product yields are decreased by addition of inert gases, or by increasing the reactant pressure. Yields are also reduced by the addition of oxygen, which affects some products similarly but others to a greater extent than nitrogen, Using this effect to distinguish between products formed by molecular and free radical reactions, a primary scheme of six reactions is postulated and the primary quantum yields determined (table 2). The major reactions are cleavage of the C—C and the β C—H bonds in the ratio 1.2 : 1. The overall quenching is attributed to deactivation of an excited intermediate state, the lifetime of which has been estimated. The intermediate is thought to be a Rydberg state.