Carbon dioxide in alkaline solution

Meldon, J.H., Smith K.A., and Colton C.K. The effect of weak acids upon the transport of carbon dioxide in alkaline solutions. Chemical Engineering Science, 1977, 32, 939. 

I. Carbon Dioxide or Sulfur Dioxide in Alkaline Solutions... 

In the higher potential region and at lower potentials (0.5 the complete oxidation of oxalic acid to carbon dioxide in acidic solution was later established by other workers. No oxidation of oxalic acid in alkaline solutions below oxide formation was observed. 

An increase of the current density of the O2 reduction at constant potential with the micropore volume was reported for porous carbon electrodes in alkaline solutions by Schwabe and coworkers [10]. The activation of the electrodes with carbon dioxide or water vapor increased the value of A and produced a certain degree of hydrophobicity. 

The electrochemical reduction of carbon dioxide to produce fuel has often been termed by some as artificial photosynthesis. Compared to the traditional researches using alkaline solution electrolytes, porous separators, and solid metallic electrode structures, there are numerous benefits to using a cell design based on a solid polymeric ion-conduction MEA with porous catalytic electrodes. In this part, we will introduce a typical example of hydroxide-ion-conduction membrane used for electrochemical conversion of carbon dioxide in alkaline PEM cells, conducted by Valdez and coworkers [132],... 

Tungsten oxydichlofide [13520-76-8], WO2CI2, a pale-yeUow crystalline soHd having an mp of 266°C, is soluble in cold water and in alkaline solution, although partly decomposed by hot water. It is prepared by the action of carbon tetrachloride on tungsten dioxide at 250°C in a bomb (13). 

In many applications of mass transfer the solute reacts with the medium as in the case, for example, of the absorption of carbon dioxide in an alkaline solution. The mass transfer rate then decreases in the direction of diffusion as a result of the reaction. Considering the unidirectional molecular diffusion of a component A through a distance Sy over area A. then, neglecting the effects of bulk flow, a material balance for an irreversible reaction of order n gives ... 

This reaction serves as a known model reaction to characterize mass transfer efficiency in micro reactors [7]. As it is a very fast reaction, mass transfer can be analysed solely The analysis can be done simply by monitoring color changes from pH indicators. Ammonia absorption in aqueous acidic solutions generally is even faster than carbon dioxide absorption in alkaline solutions. 

Whether for a class demonstration, a practical joke, or perhaps a clandestine activity, disappearing ink is a fascinating substance. What is the secret to its action One formulation of disappearing ink contains a common acid-base indicator, that is, a substance that by its color shows the acid or basic nature of a solution. One acid-base indicator that shifts from a colorless hue under acidic conditions to a deep blue color in alkaline solutions is thymolphthalein. If the indicator starts off in a basic solution, perhaps containing sodium hydroxide, the typical blue color of an ink is perceived. How does the ink color disappear This behavior is dependent upon the contact of the ink with air. Over time, carbon dioxide in the air combines with the sodium hydroxide in the ink solution to form a less basic substance, sodium carbonate. The carbon dioxide also combines with water in the ink to form carbonic acid. The indicator solution responds to the production of acid and returns to its colorless acid form. A white residue (sodium carbonate) remains as the ink dries. 

Various workers have discussed the determination of total alkalinity and carbonate [ 10-12], and the carbonate bicarbonate ratio [ 12] in seawater. A typical method utilises an autoanalyser. Total alkalinity (T milliequivelents per litre) is found by adding a known (excess) amount of hydrochloric acid and back titrating with sodium hydroxide solution a pH meter records directly and after differentiation is used to indicate the end-point. Total carbon dioxide (C milliequivelents per litre of HCO3 per litre) is determined by mixing the sample with dilute sulfuric acid and segmenting it with carbon dioxide-free air, so that the carbon dioxide in the sample is expelled into the air segments. The air... 

Protection from Carbon Dioxide.—In working with substances in alkaline solutions, it is sometimes necessary to protect the solution from the carbon dioxide in the air. This is particularly true when compounds are present that can form insoluble carbonates. In all such cases, the operations involved must be carried out in closed vessels containing air that has been purified by drawing it over a suitable absorbent such as soda lime. When... 

The principal features of the electrochemistry and construction of oxygen electrodes in alkaline solution, which were considered in Chapter 3 for primary cells, are common to secondary cells. If air is used rather than oxygen, it is then necessary to scrub the gas to remove carbon dioxide, since otherwise the electrolyte becomes progressively contaminated with carbonate which reduces the conductivity and may block electrode pores. 

A much more useful method for the preparation of a variety of substituted thiophenes and benzo[6]thiophenes in good yield depends on the oxidative cyclization of 1,3-diene-1-thiols (3) to the substituted thiophenes (4). This reaction was first reported (13CB1903) for the oxidation of o-mercaptocinnamic acid (5) to form benzo[6]thiophene (8) in good yield, using an aqueous alkaline solution of potassium ferricyanide. The intermediacy of a sul-fenium ion (6) was suggested, in view of the quantitative loss of carbon dioxide in the final product. 

Tri-4-hydroxytri-3-methyltriphenylselenonium oxide occurs when the corresponding chloride in alkaline solution is treated with carbon dioxide or dilute acetic acid. It is an amorphous powder, decomposing at 236° C. Its solution in alkali gives the nitrate when treated with nitric acid. This decomposes at 224° C. 

Maleic anhydride decomposes exothermically, evolving carbon dioxide, in the presence of alkali- or alkaline earth-metal or ammonium ions, dimethylamine, triethylamine, pyridine or quinoline, at temperatures above 150°C [1], Sodium ions and pyridine are particularly effective, even at concentrations below 0.1%, and decomposition is rapid [2], An industrial incident involved gas-rupture of a large insulated tank of semi-solid maleic anhydride which had been contaminated with sodium hydroxide. Use of additives to reduce the sensitivity of the anhydride has been described [3], Accidental transfer of an aqueous solution of sodium 2-benzothiazolethiolate into a bulk storage tank of the anhydride led to eventual explosive destruction of the tank [4],... 

Carbon dioxide (C02, melting point -56.6°C at 76 psi - 527 kPa, density 1.9769 gL at 0°C) is a colorless, odorless gas. Solid carbon dioxide sublimes at -79°C (critical pressure 1073 psi, 7397 kPa, critical temperature 31°C). High concentrations of the gas do cause stupefaction and suffocation because of the displacement of ample oxygen for breathing. Carbon dioxide is soluble in water (approximately 1 volume carbon dioxide in 1 volume water at 15°C), soluble in alcohol, and is rapidly absorbed by most alkaline solutions. 

Bradshaw A.L. and Brewer P.G. (1988b) High precision measurements of alkalinity and total carbon dioxide in seawater by potentiometric titration - 2. Measurements on standard solutions. Mar. Chem. 24,155-162. 

For anodic processes the choice of materials for the electrode is much more limited than for cathodic ones, as the anode could bo easily attacked by the products of the electrolysis (chlorine, oxygon etc.), or electrochemioally dissolved. In alkaline solutions the selection will be restricted to the application of platinum (or alloys of platinum with irridium or rhodium), palladium, carbon (or rather graphite) iron and nickel, while for acid solutions only metals of the platinum group and graphite will be suitable in a special case of the electrolysis in sulphuric acid solutions lead has found wide use, it getting coated with a conductive film of lead dioxide. 

Habermann, on electrolyzing the alcohol in alkaline solution, obtained, besides carbon dioxide, an aldehyde resin (Ludersdorf and Connel 6) from which he isolated a body closely related to cinnamic aldehyde. In aqueous solution, on the addition of potassium acetate, the alcohol was split up into ethane, potassium ethyl-carbonate, carbon dioxide, and acetic ester. 

---