CO2 gas bubbles

H. Yang, T. S. Zhao, and Q. Ye. In situ visualization study of CO2 gas bubble behavior in DMFC anode flow fields. Journal of Power Sources 139 (2005) 79-90. 

Typical procedure. O-A-PhenylbutYl-O -butyl carbonate 989 [711] To 4-phenyl-l-buta-nol 985 (100 mg, 0.67 mmol) in anhydrous DMF (1.6 mL, 0.4 m) were added cesium carbonate (625 mg, 2.10 mmol, 3 equiv.) and tetrabutylammonium iodide (208 mg, 0.67 mmol, 1 equiv.). CO2 gas (flow rate 25-30 mL min ) was bubbled into the reaction mixture for 2-3 min, and then 1-bromobutane 988 (274 mg, 0.22 mL, 2.0 mmol) was added to the suspension. The reaction proceeded at ambient temperature with CO2 gas bubbling for 3.5 h, after which time the starting material (4-phenyl-l-butanol) had been consumed. The reaction mixture was then poured into water (30 mL) and extracted with hexanes/EtOAc (3 1 v/v, 60 mL). The organic layer was washed with water (2 x 30 mL) and brine (30 mL), and dried over anhydrous sodium sulfate. Evaporation of the solvent followed by flash column chromatography (hexanes/EtOAc, 9 1 v/v) afforded 0-4-phenylbutyl-0 -butyl carbonate 989 (157 mg, 94%) as a colorless oil. 

Figure 32.6 Schematic diagram (a) and TEM images (b and c) of hollow mesoporous silica spheres prepared via emulsion technology assisted by CO2 gas bubbles. (Reproduced with permission from Refs [68,69].)...

Carbonated beverages illustrate what happens when a dissolved gas undergoes a rapid drop in pressure. Soft drinks, soda water, and champagne are bottled under several atmospheres pressure of carbon dioxide. When a bottle is opened, the total pressure quickly falls to 1 atm. At this lower pressure, the concentration of CO2 in the solution is much higher than its solubility, so the excess CO2 forms gas bubbles and escapes from the liquid. As the photo shows, this process can be dramatic. 

The large change of shapes of the base line and the very large negative peak around 1600 cm are due to the decrease in the amount of water between the window and the electrode. The decrease in water seemed to be caused partly by the reaction with methanol, but mainly by CO2 gas evolution because between the window and the electrode, there is not enou solution to dissolve all the CO2 formed on the electrode. Indeed, gas bubbles were seen in these high concentration methanol experiments, which were not foimd in 0.1 M methanol experiments. 

CO2 is measured by acidifying a seawater sample. This converts all the bicarbonate and carbonate ion into CO2. The CO2 gas is stripped out of the water sample by bubbling with an inert gas and then swept through either a coulometer or infrared analyzer for quantification. Alternatively, 2CO2 can be calculated from two easily measurable concentrations, pH and alkalinity. (See the online appendix on the companion website for the equations.)... 

Ebullition is the process by which gas bubbles form from volatile solutes in solution and rise to the surface and atmosphere. Bubbles form spontaneously when a solution becomes supersamrated with a volatile solute. Rates of formation of bubbles and ebullition depend on the volatility of the particular solute as well as its concentration in solution. In a soil producing methane, for example, although CH4 and CO2 may be generated in equal proportions (Chapter 5), gas bubbles will contain a large excess of CH4 over CO2 because CH4 is about 20 times more volatile than CO2. 

Once issued from the fiber tip, the bubble rises because of buoyancy and grows because CO2 gas diffuses into the bubble. Expansion as a bubble rises to lower pressure also contributes to the bubble size increase, but the effect is negligible in the case of champagne and beer bubbles. To understand the ascent dynamics, it is necessary to know the viscosity of beer and champagne. Beer viscosity depends on its sugar content. A typical viscosity of beer is about 1.44 times that of pure water (Zhang and Xu, 2008). If the temperature is 9°C, the viscosity is 0.0019 Pa s. The ascent velocity of a bubble depends on its size (the specific size limit is based on the physical property of beer) as follows ... 

Adsorption layer in equilibrium with the CO2 gas into the bubble and where Henry s law locally applies. 

The polymer is saturated with carbon dioxide (CO2) under high pressure. As the pressure is released, the gas bubbles that form become the pores of the foam. 

Sodium hydrogen carbonate, NaHC03, is called baking soda because it reacts with acidic substances in food to yield bubbles of CO2 gas that cause dough to rise ... 

Foams can be made by releasing a gas within a foamable liquid. For example, the opening and pouring of a bottle of soda releases pressurized CO2 gas, producing foam bubbles. Chemical reactions can also generate bubbles within the liquid. Other methods of foam production are to force both liquid and gas through a packed column (Khan et al. 1988), to spray foamable liquid onto a screen on which a fan is blowing (Aubert et al. 1986), or to use the foam-extrusion process (Han 1981). 

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