Showing papers on "Carbonic acid published in 1975"

Carbonic Acid Corrosion of Steel

Abstract: The relation between the corrosion rate of steel in carbonic acid and the CO2 partial pressure was determined by means of weight loss and polarization resistance measurements. This relation is compared with that expected for completely dissociated acids, and appears to be significantly different. A theoretical analysis of this effect shows that it can be quantitatively explained if the direct reduction of undissociated carbonic acid is the rate-determining step in the cathodic process. Both anodic and cathodic processes have been further studied by means of potentiodynamic polarization curves. The effect of temperature on the corrosion rate can be analyzed in terms of an activation energy for the overall corrosion process.

The first lonization constant of carbonic acid from 25 to 250°C and to 2000 bar

Abstract: The apparent first ionization constant of carbonic acid has been determined by conductivity measurements and found to vary from 4.32×10−7 at 25°C to 1.6×10−8 at 250°C. The pressure effect to 2000 bar has been measured, and the ratio Kp/K1 is 7.3 at 25°C and 19 at 250°C. The standard partial molar volume change for the ionization at 1 bar, $$\Delta \bar V_1^0$$ , increases from −27.6 cm3-mole−1 at 25°C to −88 cm3-mole−1 at 250°C. The volume changes are smaller at higher pressures. A linear correlation between $$\Delta \bar V_1^0$$ and the partial molar compressibility for the ionization reaction has been noted. A similar correlation exists between the partial molar entropy and volume changes for the reaction.

Acid‐base relationships within the avian egg

Abstract: Summary 1. In the newly laid egg of the domestic fowl the pH values of the albumen and yolk are about 7.6 and 6.0 respectively. 2. When the egg is stored in air there is a loss of carbon dioxide from the albumen and the pH of this fluid rises to a maximum value of about 9.5. A large proportion of the carbon dioxide which remains in the albumen is in the form of carbonate. 3. In the fertile incubated egg the pH of the albumen attains a maximum value within a period of about 2 days; the albumen then becomes less alkaline and it is nearly neutral by the end of the second week. The increasing acidity of the albumen can be attributed to (a) the secretion of hydrogen ions by the blastoderm and (b) the output of carbon dioxide by developing tissues. 4. During the first 2 weeks of incubation the pH of the yolk progressively increases to a maximum value of about 7.5: there is then a tendency for the pH of this fluid to fall and the yolk that is retained within the body of the hatched chick is slightly acidic. 5. The embryo may never come into direct contact with either the albumen or the yolk when the pH of these fluids are high and low respectively. At the beginning of embryonic development the blastoderm is separated from the albumen by the vitelline membrane and from the yolk by a layer of subgerminal fluid with a maximum pH of about 7.8. The vitelline membrane ruptures on day 4 but by this time the embryo is bathed in amniotic fluid with a pH of about 7.5. 6. The pH of amniotic fluid falls from a maximum value of about 7.5 during week I to a minimum value of about 6.5 during week 2. Amniotic fluid is a simple solution of salts until day 12; albumen then begins to flow into the amniotic cavity and the buffering capacity of amniotic fluid increases. 7. The principal end-product of nitrogenous metabolism in the chick embryo is uric acid and about 100 mg of this substance are deposited within the allantoic cavity. The pH of allantoic fluid may exceed 7.5 during week 1 but falls to 6.0 or below after day 13. 8. The tension of carbon dioxide within the egg is determined by the ratio of the rate of carbon dioxide production by the embryo to the permeability of the shell towards carbon dioxide. For the greater part of the period of incubation the permeability of the shell towards carbon dioxide is constant. Thus, as the carbon dioxide output of the embryo increases, the carbon dioxide tension within the egg rises. 9. The pH of the blood can be defined in terms of the ratio of the bicarbonate concentration to the carbon dioxide tension. There is a progressive increase in the carbon dioxide tension of the blood during the period of incubation but the pH is maintained at about 7.4 by an increase in bicarbonate concentration. 10. Part of the increase in bicarbonate is due to the removal of hydrogen ions from carbonic acid by haemoglobin. There is also a large influx of bicarbonate into the blood, but the source of this bicarbonate is not known; the evidence that renal mechanisms are involved is inconclusive and it is probable that the embryo utilizes the enormous potential store of bicarbonate in the egg shell.

Processes of nutrient transfer in a tropical rain forest

Abstract: The process of cation leaching in a tropical soil was investigated at Finca La Selva, Costa Rica. It was concluded that carbonic acid is the agent responsible for most cation leaching in this soil, just as it is in a temperate Douglas-fir forest soil in western Washington. Calculated carbon dioxide pressures in the tropical soil are approximately an order of magnitude greater than those in the temperate soil; thus it is presumed that the greater soil carbon dioxide production in the tropical soil has played a major role in depleting the reserve of exchangeable cations therein. Carbon dioxide evolution studies conducted at the site indicate that probably less than half the total soil carbon dioxide evolved comes from initial litter decomposition. Consequently, high decomposition rates cannot necessarily be directly related to high soil-leaching potential. Other aspects of mineral transfer in solution are discussed with special reference to storm duration, storm intensity, and uptake by vegetation. IT HAS LONG BEEN KNOWN that litter decomposition rates are greater in the tropics than in temperate regions (Jenny eXt al. 1949), a fact that must have a profound effect on the mineral cycling schemes of the two regions. In some tropical rain forests, for instance, base saturation is below 5 percent (Bourgeois et al. 1972), and presumably most of the nutrient capital lies in the forest biomass (Jordon 1970; Edmisten 1970). Therefore it appears that rapid and efficient uptake of minerals released from decomposing litter occurs, thus preventing further depletion of the total nutrient capital. In addition, rapid decomposition may aggravate nutrient loss by producing greater amounts of carbon dioxide (CO2), which in turn will result in higher carbonic acid concentrations in the soil solution. McColl (1969) has shown that carbonic acid is responsible for most soil-leaching losses from a 45-year-old Douglas-fir forest in western Washington. As a wetting front enters the soil, it encounters the high levels of gaseous C02 normally present in the soil atmosphere. According to Henry's law, C02 enters this incoming solution until the concentration of dissolved CO2 is proportional to the partial pressure of gaseous C02 in the soil, according to the equation [CO2 (aq) I K,Pco2, where Khl is Henry's law constant. Aqueous C02 hydrolizes with water to

Activity coefficients of bicarbonates and carbonates in seawater1

Abstract: The total (stoichiometric) activity coefficients of bicarbonate and of carbonate ions were determined in seawater by a method that is independent of ion-pairing models and used in conjunction with estimates of the coefficients of major cations to calculate the mean activity cocfficicnts of bicarbonate and carbonate salts. The total ( stoichiometric) activity coefficients of bicarbonate and of carbonate ions in seawater were dctcrmined as a function of the salinity from the ratios of the thermodynamic and the apparent dissociation constants of carbonic acid. This method made it unnecessary to resort to ion-pairing models and, thus, permitted the avoidance of many assumptions. The coefficients were used in conjunction with estimated ones for some of the major cations of seawater, introducing at this stage specific ionic interaction models, to calculate the first reported values of the mean activity coefficients of bicarbonate and of carbonate salts in seawater. Data on single ion and mean activity coefficients are of use in physicochemical studies such as the interpretation of the solubility behavior of minerals in seawater. Free activity coefficients are those that are obtained in unassociated solutions and, in solutions in which specific ionic intcractions occur, are a construct that corresponds to the effects of the ionic strength alone. Total activity coefficients, on the other hand, are those mcasurcd in the presence of specific interactions and are related to free ones, when the ion-pairing model is used (Pytkowicz et al. 1966; Pytkowicz 1969)) by

Blowing agent mixture

Abstract: The invention refers to a blowing agent composition consisting of 1,4 butan-diol-bis-(carbonic acid ester-benzoic acid anhydride) and silicon dioxide. Silicon dioxide reduces the decomposition temperature of the anhydride while at the same time increasing the yield of gas substantially.

Carbonic Acid and its Derivatives

Abstract: Publisher Summary This chapter discusses carbonic acid and its derivatives, a large and diverse group of compounds. Metacarbonic acid and its esters, such as carbon dioxide, esters of carbonic acid, anhydrides of primary esters of carbonic acid, mixed anhydrides of primary carbonates, and mono-carboxylic acids are also profiled with detailed information on general methods of preparation, properties, and typical reactions. Halides of carbonic acid, sulfur analogues of carbonic acid, and their derivatives, such as carbon oxysulfide and carbon disulfide, thiocarbonic acids and their halides, such as thiophosgene, amides, and related derivatives of carbonic acid, and the thiocarbonic acids are illustrated in a systematic manner. Special stress is evident in the discussion on urea and its derivatives, such as halogenoureas, ureides, and so on because of its commercial relevance as a fertilizer. Derivatives of iminodicarboxylic acid, such as biuret and nitrilotricarboxylic acid, sulfur analogues of carbamic acid, and hydrazino, azo, and azido derivatives of thiocarbonic acid are also emphasized in this chapter. Sulfur compounds of cyanogens, such as thiocyanic acid, cyanamide and its derivatives, and derivatives of carbodi-imide and orthocarbonic acid are also covered.

Method for the preparation of salts of carbonic acid monoesters

Abstract: A method is disclosed for preparing salts of monoesters of the carbonic acid, the improvement consisting in that the alcohol corresponding to the monoester is reacted with carbon dioxide and a halide of a metal of the Groups IA, IIA, IIIA and IIB of the Periodic Table, the reaction being effected in the presence of a nitrogenous, aliphatic, aromatic or heterocyclic base.

Reviewing acid-base balance.

Abstract: the chemical reactions of body fluids become too acid or too alkaline. An acid, a substance that contains hydrogen ions that can be given off or donated to other substances, is called a proton donor. A base can receive a hydrogen ion and is a proton acceptor. For example, H2C03, or carbonic acid, can give off or donate H+ (hydrogen ion) and the proton acceptor HCO3, (bicarbonate or base) can accept the H+. The quantity of hydrogen (H+) present in body fluids largely determines acid-base balance. But since

6-Sulphonamido-penicillanic acid derivs - prepd. by reacting 6-APA with an activated sulphonic acid

Abstract: 6-Sulphonamido penicillanic acid derivs. of formula (I) (where R is an undefined residue), e.g. 6-(p-acetamidobenzenesulphon-amido)-penicillanic acid, are new cpds. They may be prepd. by activating a sulphonic acid R-SO3H and condensing the product with 6-amino penicillanic acid (6-APA). (I) have antibiotic activity. Activation of the sulphonic acid RSO3H can be effected by (a) converting into a mixed anhydride with carbonic acid, e.g. by reacting with ClCOOEt in the presence of NEt3, or (b) converting into RSO2Cl. The sulphonic acid used may be an aliphatic, aromatic, carbocyclic or heterocyclic sulphonic acid.

Thermoplastic carbonate-modified copolyesters and a process for their preparation

Abstract: Carbonate-modified copolyesters which are suitable for the production of mouldings by injection moulding or for the production of pipes, films and fibers by extrusion, can be obtained by reacting aromatic dicarboxylic acids or their ester-forming derivatives and carbonic acid esters of dihydric aliphatic alcohols which have carbonic acid ester groupings in the molecule and hydroxyalkyl end groups.