Carbon Monoxide Oxygen Research Articles

A Carbon Monoxide-Oxygen Sampler for Evaluation of Fire Fighter Exposures

A self-contained personal, sampler has been developed to monitor firefighters’ exposure to both carbon monoxide and oxygen in actual fires. A combustible gas detector was modified to be specific for carbon monoxide measurements in the range of 0.02 to 10.0%. A membrane sensor is used to measure oxygen in the range of 0 to 21%; the data are recorded on a small cassette tape recorder with a voltage-to-frequency converter. Tests on actual fire gases indicate mean errors of 14.0% and 3.2% in the carbon monoxide and oyxgen measurements, respectively.

High-temperature oxidation of CO and CH 4

The oxidation of moist carbon monoxide and the post-induction-phase oxidation of methane were studied in a turbulent flow reactor. Reactants, stable intermediates, and products were determined spatially by chemical sampling and gas-chromatographic analysis. The carbon monoxide-oxygen reaction in the presence of water was studied at atmosphericpressure, and over the following ranges: temperature, 1030°–1230°K; equivalence ratio, 0.04–0.5; and water concentration, 0.1%–3.0%. The over-all rate expression found was − d [CO]/ dt =10 14.6±0.25 exp[(−40,000±1200)/ RT ][CO] 1.0 [H 2 O] 0.5 [O 2 ] 0.25 mole cm −3 sec −1 . The data support the fact that hydroxyl radical concentration in the reaction exceeds that at thermal equilibrium by as much as 2 orders of magnitude. The post-induction-phase reaction of methane and oxygen was studied at atmospheric pressure, over the temperature range of 1100°–1400°K and equivalence ratio range of 0.05–0.5. The over-all methane disappearance-rate expression was found to be − d [CH 4 ]/ dt =10 13.2±0.20 exp[(−48,400±1200)/ RT ][CH 4 ] 0.7 [O 2 ] 0.8 , mole cm −3 sec −1 . The rate was shown to be independent of water concentrations added initially or produced in the reaction. The over-all appearance rate of carbon dioxide in the methane-oxygen reaction is described by d [CO 2 ]/ dt =10 14.75±0.40 exp[(−43,000±2200)/ RT ][CO] 1.0 [H 2 O] 0.5 [O 2 ] 0.25 mole cm −3 sec −1 . This correlation represents rates of carbon dioxide formation 3.5 times slower than those found in the independent study of the moist carbon monoxide reaction. From these and other experiments it was possible to deduce thatCH 4 +OH→CH 3 +H 2 O (3) is not the only mechanism contributing to the observed rate of disappearance of methane. It was concluded that the reaction CH 4 +O→CH 3 +OH (4) is of major importance in both oxygen-and fuel-rich systems at high temperatures. Furthermore, the experimental data support that these two reactions, as well as CH 3 +H 2 →CH 4 +H (−5) contribute to the methane results reported here.

Anaerobiosis and the oxygen debt in an anuran amphibian,Rana esculenta (L.)

(1) Artificially ventilated curarised frogs consumed 23% less oxygen than animals breathing naturally but their respiratory quotient was significantly increased. Artificial ventilation maintained arterial oxygen tension at normal levels but arterial carbon dioxide tension fell significantly. When 90% of the haemoglobin was combined with carbon monoxide oxygen consumption was reduced by 40% and the respiratory quotient was increased. (2) During apnoea both normal animals and those exposed to carbon monoxide showed reductions in oxygen uptake of about 45%. Heart rate also declined by 20–40%. During apnoea respiratory quotient of both groups of animals was significantly elevated. In normal animals arterial and venous oxygen tensions fell during apnoea, arterial tensions to 20% of the ventilation value and venous oxygen tensions to a slightly higher value. Arterial oxygen content fell from 9.6 vols % to 3 vols %. Arterial carbon dioxide tensions and contents increased during the apnoea and arterial pH fell. (3) When ventilation was restored frogs consumed about 109–130 μl more oxygen in the first 10 min than in comparable periods before the apnoea. However, animals with 90% of the haemoglobin combined with carbon monoxide showed only a gradual return to the pre-apnoeic level of oxygen consumption. Heart rate, respiratory quotient and blood gas tensions returned to pre-apnoeic levels within 30 min of the resumption of artificial ventilation. The excess oxygen consumed during the first 10 min was equal to the amount of oxygen calculated to have been removed from the oxygen store of the blood during apnoea. (4) It is concluded that the blood has a function in maintaining oxygen metabolism in both ventilated and apnoeic frogs but that oxygen stores, including that of the blood, make little contribution to oxygen metabolism during apnoea and appear to be replenished immediately lung ventilation is restored.

The conversion of pyrrolizidine alkaloids to N-oxides and to dihydropyrrolizine derivatives by rat-liver microsomes in vitro

The enzymatic conversion of pyrrolizidine alkaloids to dihydropyrrolizine derivatives (‘pyrrole derivatives’) and to N-oxides has been investigated. In rat liver both reactions were catalysed by an enzyme present in the microsomal fraction, typical of the mixed-function oxidases. Thus the conversion of alkaloids to pyrrole derivatives and to N-oxides required oxygen and reduced NADP and was activated by Mg 2+, Mn 2+ or Ca 2+ at concentrations of 5 · 10 −3 M. The liver microsomal system was less active in the female rat than in the male and was inhibited by carbon monoxide and by SKF 525A. The conversion of retrorsine to both pyrrolic metabolites and to N-oxides was significantly induced by pretreatment with phenobarbitone or DDT, but the induction of pyrrole derivatives was greater than that of N-oxide. The conversion of retrorsine to pyrrole derivatives was lower in liver microsomal fractions from rats which were starved or fed on protein-free diets. Differences between the rates of formation of pyrrole derivatives and N-oxides followed the inclusion of nicotinamide in the incubation mixtures containing microsomes from untreated rats, or substitution of a carbon monoxide-oxygen mixture for air during the incubation period. The K m values towards the formation of pyrrolic derivatives and N-oxides from retrorsine from normal rat-liver microsomes were similar. No conclusive evidence was found to establish whether N-oxides were intermediate in the formation of pyrrole derivatives. However, pyrrole derivatives could not be detected when N-oxides were added to the hepatic microsomal system in vitro. Rat-liver microsomal enzymes converted a number of alkaloids having either 1,2-dehydropyrrolizidine or saturated pyrrolizidine ring structures to pyrrole derivatives. The pyrrole derivatives from these two groups of alkaloids had different chemical properties. Only alkaloids in the first group were hepatotoxic, and in general the more toxic alkaloids in this group were those from which the greatest amounts of pyrrole derivatives were produced in vitro, although there were exceptions. The enzymatic conversion of retrorsine or monocrotaline to pyrrolic derivatives could not be demonstrated in lung microsomal fractions.

The effect of oscillatory combustion on the formation of atmospheric pollutants

The difference between the relaxation times of the mechanical and thermal transport processes which occur in flow combustors often leads to a coupling phenomenor, which may result in severe acoustical oscillations. Previously reported experiments have indicated that the concentrations of certain chemical species may be significantly affected by these pressure-temperature oscillations. Some chemical species, such as the oxides of nitrogen, which are apparently enhanced, are directly involved in the formation of atmospheric pollutants and chemical smog. Because oscillatory combustion occurs in many industrial applications, an understanding of the complex chemical thermodynamics of combustion systems is very important. In this work approximate integration techniques have been employed to solve the set of simultaneous kinetic rate equations which describe the oscillatory combustion of certain hydrocarbons. The dynamic concentrations for each chemical species have been calculated as a function of time and position in a model flow combustor. Three chemical systems were investigated: the combustion of carbon monoxide in oxygen, the combustion of carbon monoxide in air, and the products of the combustion of methane in air. In addition, calculations of the point-to-point equilibrium concentrations for the chemical systems investigated were made for comparison. Some major conclusions reached as a result of this analytical study were as follows: 1. Pressure-temperature oscillations significantly affect the concentrations of several “trace” components which contribute to air pollution. 2. The amplitude of the temperature oscillations seems to be of more importance than the frequency of the oscillations for the particular combustor model chosen for this study. The effects due to amplitude become more significant with increased temperature. 3. Deviation from equilibrium in flow combustors is very significant for important trace components such as monatomic oxygen and nitric oxide.

The three-dimensional detonation polar and an application to spinning detonation

Expressions are derived for a three-dimensional polar in the pressure ratio, deflexion angle space to represent conditions downstream of a detonation wave with given upstream conditions. An analysis of reflected waves is undertaken and the representation of three wave confluences in a three-dimensional hodograph space studied. These techniques are applied to experimental results available for spin detonation in gaseous mixtures of acetylene-oxygen-argon and carbon monoxide-oxygen. Assumptions made in earlier papers concerning local extinction of combustion at the confluence point are not necessary in this picture.

Studies on reduction of azo-linkages in human placental homogenates

Investigations of the capacity of human placental tissue to metabolize exogenous substrates revealed a system present in the soluble fraction of placental homogenates which increased the NADPH-dependent reduction of the azo-linkage of neoprontosil. Characterization of the enzyme system involved indicated striking differences in comparison to the azo-reductase system(s) present in hepatic tissues. Activity of the placental system was not affected by additions in vitro of magnesium ion, nicotinamide, NADP or NAD, and was only very slightly inhibited when incubated under atmospheres of pure oxygen of carbon monoxide. Placental azo-linkage reduction was enhanced by addition in vitro of EDTA, reduced glutathione and glucose 6-phosphate. The addition in vitro of flavins resulted in a decreased rate of conversion of neoprontosil to sulfanilamide. Flavin mononucleotide appeared to possess the greatest inhibitory effect. The system was also inhibited by sulfhydryl reagents. Comparisons of specific activities from homogenates of tissue obtained early in the gestational period vs. that obtained at term revealed no statistically significant differences. Studies on the mechanism of increased azo-linkage reduction revealed that an enzymicnonenzymic system involving d-glucose 6-phosphate: NADP oxidoreductase (EC 1.1.1.49) and 6-phospho- d-gluconate: NADP oxidoreductase (EC 1.1.1.44) could account for this increase in azo-linkage reduction.

A photoelectric study of the low pressure explosion limit of the wet carbon monoxide-oxygen reaction

The so-called low pressure glow and explosion limits of the water-catalysed reaction between carbon monoxide and oxygen have been studied using a photomultiplier to obtain light intensity/time graphs. The results show no sign of a glow limit, and little discontinuity at the explosion limit. The effects of mixture composition, changes of surface, vessel packing, addition of inert gases and replacement of protium by deuterium oxide have been investigated. It is suggested that the reaction involves degenerate chain branching and the formation of a semi-stable intermediate, and that diffusion of radicals to the walls is not the most important step in chain termination.

Ignition kinetics of the carbon monoxide-oxygen reaction

An analytic solution for the ignition kinetics of the dry CO−O2 reaction is obtained by assuming an initiation reaction followed by the chain-branching steps C O + O → C O 2 * C O 2 * + O 2 → C O 2 + 2 O together with chain termination by quenching of CO2* and three-body recombination of CO and O. It is concluded that shock-tube induction times on reportedly dry CO−O2 mixtures cannot be explained by this mechanism. The shock-tube data can be explained by the following scheme, if a water vapor content of 20 ppm or less is assumed: C O + O 2 → k i C O 2 + O O + H 2 O → k 5 2 O H O H + C O → k 6 C O 2 + H H + O 2 → k 2 ' O H + O The rate constant for the initiation reaction was found to be k i = 2.5 × 10 9 exp ⁡ ( − 48 , 000 / R T ) l i t e r s m o l e − 1 sec ⁡ − 1 . The rate constant for the reaction between O and H2O at 1600°K was estimated by two different methods to be 8×108 and 1.5×109 liters mole−1 sec−1. Induction periods for mixtures with deliberate additions of hydrogen can be fit by adding the steps O + H 2 → k 3 ' O H + H O H + H 2 → k 1 ' H 2 O + H

Gas chromatography and pulmonary diffusing capacity measurements

A gas chromatographic system is described which accurately measures low levels of neon and carbon monoxide in high concentrations of oxygen. The system contains a special parallel column package used in conjunction with a venting valve. Accurate reproducible analyses for Ne, CO, CO2, O2 and N2 are obtained from a single 10-ml gas sample. respiratory gas analysis; carbon monoxide in oxygen, determination; neon in oxygen, determination Submitted on December 2, 1964

Heterogeneous photocatalysis I. The influence of oxidizing and reducing gases on the electrical conductivity of dark and illuminated zinc oxide surfaces

Since the photoconductivity of zinc oxide increases with time in a carbon monoxide atmosphere and also during the subsequent evacuation under light, it must be concluded that the uptake of CO by an illuminated zinc oxide surface is understandable only if neutral CO molecules react with chemisorbed oxygen to form CO O −(ads). The decreased photoconductivity of zinc oxide due to introduction of carbon monoxide in oxygen confirms this mechanism and leads to the further assumption that a considerable portion of the chemisorbed oxygen must be present as O 2 −(ads). This assumption also explains why the half-life period t 1 2 of the dark decay in pure oxygen is proportional to 1 p O 2 The generation of charge carriers during the illumination is strongly influenced by doping zinc oxide with Li 2O and Ga 2O 3. Possible mechanisms are discussed. Since an addition of Li 2O to zinc oxide changes neither the position nor the intensity of the green luminescence band, it remains uncertain whether the donors, reacting with the electronic species, are responsible for the green luminescence light.

Carbon monoxide-oxygen atom reaction: B.H. Mahan and R.B. Solo, J. Chem. Phys., 37 (11), 1 Dec. 1962, 2669–2677.

Carbon monoxide-oxygen atom reaction: B.H. Mahan and R.B. Solo, J. Chem. Phys., 37 (11), 1 Dec. 1962, 2669–2677.

Carbon Monoxide—Oxygen Atom Reaction

The kinetics and light emission of the carbon monoxide—oxygen atom reaction have been investigated. At pressures above 0.2 mm, carbon dioxide is formed by a bimolecular association reaction which appears to violate the electron spin conservation rule. The quantum yield of the reaction is 1/350 at 298°K, and increases with increasing temperature. Evidence has been found that excited carbon dioxide molecules can participate in chain branching processes.

Oxygen dependency of in vivo photophosphorylation.

THE mechanism by which ATP is formed when the intact green is illuminated is not yet fully understood. ATP formation in isolated chloroplasts has been shown to be dependent on illumination1and has been shown to proceed by either a cyclic or a non-cyclic process depending on the oxido-reduction catalysts used2. Chloroplasts are capable of photophosphorylation at low rates in the absence of catalysts. This endogenous activity has been demonstrated to be oxygen dependent3,4. Ion-exchange chromatographic studies of the ATP content of intact barley seedlings show that the steady-state level of ATP in light is several fold that in dark5. The level with illumination drops if the leaves are exposed to nitrogen or to carbon monoxide–oxygen mixtures. This was interpreted as evidence that formation of ATP in barley seedlings in light was an oxidative process, using molecular oxygen as a terminal electron acceptor.

Dosage chromatographique de l'oxygene et de l'argon aux faibles concentrations dans les gaz caloporteurs

A study of the conditions for Chromatographie analysis of a mixture of oxygen and argon led to the choice of a column of 5 Å molecular sieves, thermostated at — 78° C (with a resolution factor R = 1.85). The method was then used for the analysis of traces of these gases in helium, carbon dioxide and nitrogen. Thanks to techniques of concentration and of permuting columns, it was possible to analyse quantities of the order of 1 vpm of oxygen or argon in helium and carbon monoxide and 50 to 80 vpm in nitrogen, even in the presence of other normal impurities (nitrogen, carbon monoxide, hydrogen, etc.).

Kinetic study of the carbon monoxide-oxygen reaction through the inhibition mechanism of this reaction

The gas-phase inhibition of the explosive combustion of carbon monoxide by very small amounts of inhibitor shows the ‘reactional activity’ pertaining to the carbon monoxide-oxygen system. The present paper is a contribution to our knowledge of the carbon monoxide combustion process as regards: (1) the process and kinetics of the initiation reaction, and (2) the branching factor.

Experimental Measurements and Theoretical Analysis of Detonation Induction Distances

Experimental measurements of the induct ion distances are given for hydrogen-oxygen, acetyleneoxygen, acetylene-air, methane-oxygen, carbon monoxide-oxygen, hydrogen-oxygen-nitrogen, hydrogen-oxygen-hel ium, hydrogen-oxygen-argon, and hydrogen-oxygen-carbon dioxide mixtures at initial pressures of 1, 5, 10 and 25 a t m . An empirical relationship involving the combust ion t e m perature, burning velocity, sonic velocity in the unburned gas and Reynolds number based on the burning velocity has been established to predict detonation induction distances of certain c o m bustible gas mixtures. The correlation is not satisfactory for mixtures containing hydrocarbons; an explanation of this discrepancy is offered.

THE RESPIRATORY EXCHANGE OF DIAPAUSING PUPAE OF THE CECROPIA SILKWORM IN THE PRESENCE OF CARBON MONOXIDE

1. After due correction for complicating reactions, the rate of total gas uptake of normal diapausing pupae of the Cecropia silkworm in a carbon monoxide-oxygen mixture of 5 to 1 is found to be stimulated approximately 2-fold over the rate in air. 2. Ninety per cent of this extra gas uptake is due to a stimulation of the true respiration of the pupa. 3. The remaining ten per cent is due to the combustion of carbon monoxide to carbon dioxide. 4. The combustion of carbon monoxide is increased slightly when the metabolism of the pupa is enhanced following integumentary injury. 5. There is a slight fixation of carbon-14 in pupae under aerobic conditions presumably as a result of fixation of C14O2 manufactured from C14O by the pupa. 6. There is no detectable fixation of C14O in pupae exposed to this gas under anaerobic conditions. 7. After correction for carbon monoxide-combustion, it is clear that the enhanced oxygen uptake following integumentary injury of diapausing pupae is inhibited by carbon monoxide. 8. This carbon monoxide-inhibition is directly proportional to the enhancement of oxygen uptake following injury.

Cytological effects of phenylnitrosamines—III. The effect on X-ray sensitivity at low oxygen tensions

A number of agents structurally or functionally related to cupferron have been studied for their ability to enhance the frequency of chromosomal aberrations produced by X-rays in the presence of 1 per cent oxygen in the root-tips of Vicia faba. A marked enhancement was obtained only with agents which inhibited bean-root respiration. In experiments with the respiratory inhibitor carbon monoxide, the X-ray dose necessary to produce a given frequency of aberrations in the absence of oxygen was about 2.3 times as high as that which produced the same effect in the presence of 1 per cent oxygen. The carbon monoxide effect was light-reversible; no enhancement was obtained when the roots were exposed to strong light during irradiation and carbon monoxide treatment. Both cupferron and carbon monoxide enhanced X-ray sensitivity only when they were present before and during irradiation. Post-treatments with these agents did not have any influence on the frequency of aberrations produced by a given X-ray dose. The frequency of aberrations produced by 108 r of X-rays was almost doubled when the change from 1 per cent oxygen in nitrogen to 1 per cent oxygen in carbon monoxide was made 70 sec before irradiation. In order to be fully effective, the CO-treatment was started between 2 and 5 min before irradiation. These results support the hypothesis that cupferron and other respiratory inhibitors enhance the X-ray sensitivity of bean roots at low oxygen tensions because they prevent the formation of an oxygen gradient in the roots. A comparison between the cytological and physiological effects of cupferron, and those of some other agents which are structurally or functionally related to it, is presented in tabular form.

Second Explosion Limit of Dried Carbon Monoxide–Oxygen Mixtures

THE position of the second explosion limit of carefully dried mixtures of carbon monoxide and oxygen in quartz vessels has been determined. Both the heating and withdrawal methods were used in a static system. Carbon monoxide was prepared from sodium formate and concentrated sulphuric acid, and oxygen by heating potassium permanganate. After being passed through chemical desiccants and then through cold traps, the gases underwent a final drying operation immediately before use. This final drying consisted in allowing the gases (sometimes premixed) to stand in ‘Pyrex’ drying vessels surrounded by liquid oxygen for at least 12 hr.