Carbon dioxide diffusivity

These values are as much as one hundred times larger than those typically observed in conventional liquids. The improved transport rates in SCFs versus liquid solvents are important in practical appheations including supercritical extraction. Furthermore, carbon dioxide diffuses through condensed-hquid phases (e.g., adsorbents and polymers) faster than do typical solvents which have larger molecular sizes. 

Figure 7. Carbon dioxide diffusion from a paint film saturated with carbon dioxide (catalyst DBTDL).

The diffusion of oxygen and carbon dioxide also depends on their partial pressure gradients. Oxygen diffuses from an area of high partial pressure in the alveoli to an area of low partial pressure in the pulmonary capillary blood. Conversely, carbon dioxide diffuses down its partial pressure gradient from the pulmonary capillary blood into the alveoli. 

This entire reaction is reversed when the blood reaches the lungs. Because carbon dioxide is eliminated by ventilation, the reaction is pulled to the left. Bicarbonate ions diffuse back into the red blood cells. The hemoglobin releases the hydrogen ions and is now available to load up with oxygen. The bicarbonate ions combine with the hydrogen ions to form carbonic acid, which then dissociates into carbon dioxide and water. The carbon dioxide diffuses down its concentration gradient from the blood into the alveoli and is exhaled. A summary of the three mechanisms by which carbon dioxide is transported in the blood is illustrated in Figure 17.8. 

Alkalinisation of local anaesthetic solution with sodium bicarbonate (NaHC03) increases the pH of the solution to a value near its pKa. This results in an increased proportion of unionised drug available for neural penetration and thereby reduces the onset time. Carbonation is a term used to describe the acidification of a local anaesthetic solution with carbon dioxide. Following injection, the carbon dioxide diffuses into the axoplasm causing a decrease in the pH. This results in a higher proportion of ionised drug within the cell. In theory this should enhance the Na-i- channel block but in practice the results are disappointing. 

Inside the yeast cell the hexoses are converted principally to ethanol, carbon dioxide, and adenosinetriphosphate (ATP) with the liberation of waste heat. The ATP is an energy source in cell metabolism the ethanol and carbon dioxide diffuse across the cell wall to the exterior where the ethanol dissolves in the juice and the carbon dioxide bubbles... 

Figures 5 and 6 show the results of the calculations, and they are compared with the actual data distribution as shown by a dashed bounding line. With both calcite and dolomite, colder waters match conditions of carbon dioxide pressure greater than atmospheric, and high temperature conditions match carbon dioxide pressure nearly the same as the atmosphere. It appears the degree of mixing and the rate of carbon dioxide diffusion is of prime importance when considering approach to liquid, gas, and solid equilibrium.

An alternative is an arrangement of manometer and porous pot which effectively compares the rate of diffusion of a gas with that of air (Figure 16.1). This can be used to show that carbon dioxide diffuses slower than air and hydrogen diffuses faster. 

On the basis of these experiments it is possible to conclude that at film thicknesses of the order of micrometers, the effect of adsorption layers on the diffusion rate can be neglected (this conclusion refers mainly to carbon dioxide diffusion). 

Scientific program consists of seven sessions which cover most of possibilities of chemical conversion of carbon dioxide. As for carbon dioxide exhausts from large generation sources, it should be concentrated and separated, followed by the rapid conversion into valuable compounds. Once carbon dioxide diffuses into the atmosphere, it is preferable to be incorporated into the plant through the biochemical methods. For six sessions, one plenary lecture and one key note lecture were done. One special lecture was delivered by Dr. Mary Preville of lEA. 

Carbon dioxide is continually produced by cellular aerobic metabolism of glucose and fatty acids. Carbon dioxide diffuses down its concentration gradient from the cell to the blood, which carries it to the lungs. It can interact with water to form carbonic acid (H2C03), a process catalyzed by carbonic anhydrase, an enzyme present in erythrocytes. Carbonic acid can then dissociate to liberate bicarbonate ion (HCOJ) and hydrogen ion (H+) as follows ... 

Lower temperatures slow the rate of carbon dioxide loss and can leave unburned limestone in the product (Table 7.1). Also, if a moderate particle size rather than finely ground limestone is used to reduce dust carryover in the kiln, additional carbon dioxide partial pressure must be developed in the larger granules to ensure carbon dioxide diffusion to the outside. 

The carbon dioxide diffuses to the lungs and is eventually exhaled. The formation of the Hb ions (due to the reaction between HHb and HCO3 shown above) also favors the uptake of oxygen at the lungs... 

Step 5 Carbon dioxide diffuses away from the surface into the kiln gases. 

Diffusion of oxygen happens efficiently because there is a concentration gradient from air in the alveoli to blood in the capillaries the distance through the alveoli walls, tissue fluid and capillary walls is small and the total surface area of all the alveoli is large. For the same reasons, carbon dioxide diffuses in the opposite direction. 

Kholyavenko and Rubanik (143) investigated the effect of internal diffusion on the ethylene oxidation rate, using the diaphragm method, and calculated the effective diffusion coefficients for ethylene and carbon dioxide diffusing through a silver diaphragm. 

EXAMPLE 1 A gas, A. diffuses throu a porous plug at Carbon dioxide diffuses through the plug at Calculate the molar mass of A. 

A mixture of carbon monoxide and carbon dioxide diffuses through a porous diaphragm in one half of the time taken for the same volume of bromine vapour. What is the composition by volume of the mixture ... 

On the other hand, if R is greater than R, carbon dioxide diffusion occurs in the opposite... 

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