Bicarbonate-Carbon Dioxide System

Human plasma under normal circumstances has a pH of 7.4, which is maintained by a HC03 /H2C03 buffering system. H2C03 in actuality is a combination of true H2C03 and dissolved C02. Their relationship to HC03 and to each other is shown in Equation (3.17)  

In red blood cells, the enzyme that catalyzes the conversion of C02 and H20 to HC03 and H+ is carbonic anhydrase, and it plays a crucial role in maintaining the pH of the organism at a constant level. 

Example 3.5 indicates that the blood of the patient is abnormally acidic. We also note that pC02 is normal, whereas the bicarbonate is severely depressed. Because the pH is less than 7.4, the patient is said to be acidotic, and because the bicarbonate is largely responsible for this and the bicarbonate part of the Henderson-Hasselbalch equation has been termed the metabolic component, the patient is suffering from pure metabolic acidosis. This is often seen in untreated 

Treatment of acid-base disturbances requires a determination of how much acid (NH4C1) or alkali (NaHCQ3) to add to the patient s system. For this 

A patient with slow and shallow breathing had a pC02 of 58 mm Hg and a total C02 of 33.8 meq/L. What is the acid-base status  

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Additional vapor-liquid equilibrium data based on published iitformation and ejqterimen-tal work have been reported by Bocard and Mayland (1962). Other physical data on the potassium carbonate-potassium bicarbonate-carbon dioxide system are shown in Figures 5-11 to 5-14. The data of Bocard and Mayland (1962) have been converted to a series of nomographs by Mapstone (1966). 

Tosh, J. S., J. H. Field, H. E. Benson and W. P. Waynes, "Equilibrium Study of the System Potassium Carbonate, Potassium Bicarbonate, Carbon Dioxide and Water," U. S. Bureau of Mines, Report of Investigations, 1959, 5484. 

The acid-base equilibria between carbonate/bicarbonate/carbon dioxide clearly show that in vivo systems sufficient amounts of CO2 will be present such as to allow reactions to occur and point out the relevance of the reactivity of COj with biologically significant compounds. The carbonate radical anion is a strong oxidant the reacts by either H-atom abstraction or electron transfer (Eo(C03, H /HCOj) = 1.78V, where the former is generally slower than the latter. 

A large amount of comprehensive physical data on the potassium carbonate-potassium bicarbonate-carbon dioxide-water and potassium carbonate-potassium bicarbonatepotassi-um bisulfide-carbon dioxide-hydrogen sulfide-water systems is available in literature (Benson et al., 1954 Benson et al., 1936 Tosh et al., 1959 Tosh et al., 1960 Allied Chemical Coip., 1961 Bocard and Mayland, 1962). Some typical data are given below however, fm complete information, the reader is referred to the original sources. 

Both potassium nitrate (0.5%) and potassium chromate (0.2%) are very effective in carbon dioxide systems, but not with hydrogen sulfide. Use of metavanadate in hot carbonate systems can passivate steel in a carbonate solution only when the bicarbonate content is low. The addition of oxygen to the system increases passivation of mUd steel, but increases corrosion of copper-nickel alloys. 

Ammonium bicarbonate, sp gr 1.586, formula wt 79.06, is the only compound in the NH —CO2—H2O system that dissolves in water without decomposition. SolubiUty in 100 g of H2O ranges from 11.9 g at 0°C to 59.2 g/100 g of H2O at 60°C (8). The heat of formation from gaseous ammonia and carbon dioxide andUquid water is 126.5 kj/mol (30.2 kcal/mol). Ammonium bicarbonate is manufactured by passing carbon dioxide gas... 

There are essentially two components in a chemical leavening system bicarbonate that suppHes carbon dioxide gas, and an acid which triggers the Hberation of carbon dioxide from bicarbonate upon contact with moisture (see Carbon dioxide). 

The component reactions in eqn. (2) are very fast, and the system exists in equilibrium. Additional carbon dioxide entering the sea is thus quickly converted into anions, distributing carbon atoms between the dissolved gas phase, carbonate and bicarbonate ions. This storage capacity is clear when the apparent equilibrium constants for the two reactions in eqn. (2) are examined, namely... 

The formation of a passive film of iron oxide (magnetite, Fe304), under sulfite or hydrazine reducing conditions, is optimized at pH of 11 to 12. The downside is that the decomposition of carbonates and bicarbonates produces carbon dioxide, the primary cause of condensate system corrosion. 

Where FW contains bicarbonate or carbonate alkalinity (as calcium, magnesium, or sodium salts), these salts undergo thermal decomposition in the boiler, and the steam-volatile contaminant gas carbon dioxide is introduced into the steam distribution system, as shown ... 

Carbon dioxide devices were originally developed by Severinghaus and Bradley (59) to measure the partial pressure of carbon dioxide in blood. This electrode, still in use today (in various automated systems for blood gas analysis), consists of an ordinary glass pH electrode covered by a carbon dioxide membrane, usually silicone, with an electrolyte (sodium bicarbonate-sodium chloride) solution entrapped between them (Figure 6-17). When carbon dioxide from the outer sample diffuses through the semipermeable membrane, it lowers the pH of the inner solution ... 

Carbonic anhydrase inhibitors decrease aqueous humor production by inhibition of the carbonic anhydrase isoenzyme II located in the ciliary body. In the eye, carbonic anhydrase catalyzes the conversion of water and carbon dioxide to bicarbonate and hydrogen ion, which is a significant step in aqueous humor production. Carbonic anhydrase inhibitors are available in systemic and topical preparations.10,13,14... 

CO3 species was formed and the X-ray structure solved. It is thought that the carbonate species forms on reaction with water, which was problematic in the selected strategy, as water was produced in the formation of the dialkyl carbonates. Other problems included compound solubility and the stability of the monoalkyl carbonate complex. Van Eldik and co-workers also carried out a detailed kinetic study of the hydration of carbon dioxide and the dehydration of bicarbonate both in the presence and absence of the zinc complex of 1,5,9-triazacyclododecane (12[ane]N3). The zinc hydroxo form is shown to catalyze the hydration reaction and only the aquo complex catalyzes the dehydration of bicarbonate. Kinetic data including second order rate constants were discussed in reference to other model systems and the enzyme carbonic anhy-drase.459 The zinc complex of the tetraamine 1,4,7,10-tetraazacyclododecane (cyclen) was also studied as a catalyst for these reactions in aqueous solution and comparison of activity suggests formation of a bidentate bicarbonate intermediate inhibits the catalytic activity. Van Eldik concludes that a unidentate bicarbonate intermediate is most likely to the active species in the enzyme carbonic anhydrase.460... 

The system illustrated by (272) forms the basis of a model for the zinc-containing metalloenzyme, carbonic anhydrase (Tabushi Kuroda, 1984). It contains Zn(n) bound to imidazole groups at the end of a hydrophobic pocket, as well as basic (amine) groups which are favourably placed to interact with a substrate carbon dioxide molecule. These are both features for the natural enzyme whose function is to catalyze the reversible hydration of carbon dioxide. The synthetic system is able to mimic the action of the enzyme (although side reactions also occur). Nevertheless, the formation of bicarbonate is still many orders of magnitude slower than occurs for the enzyme. 

Figure 6-8 shows how the partial pressure of carbon dioxide in equilibrium with surface water oscillates in phase with the fluctuations in precipitation rate, saturation state, and temperature. The oscillations in alkalinity and bicarbonate concentrations have shifted in phase by about 90° because these quantities decrease when precipitation and evaporation are removing carbon from the system at above-average rates. 

Effervescence these systems that consist for instance of a carbonate or bicarbonate salt and an organic acid like e.g. citric acid, develop carbon dioxide gas on contact with water and are well known in pharmaceutical/health food tablets. A few market products exist that make use of this system but for reasons explained above this system is not that suitable for detergent tablets with a high content of surfactants. 

In this system, the least soluble component is sodium bicarbonate, so this crystallizes out. On calcination it yields sodium carbonate and the carbon dioxide is recycled. The ammonia is recovered by adding calcium hydroxide, producing calcium chloride waste and liberating the... 

In the method for extractable phosphorus [62, 64-66] the phosphorus is extracted from the soil at 20 1°C with sodium bicarbonate solution at pH8.5. After filtration and release of carbon dioxide the extracts are introduced into a flow-injection system for the determination of phosphate. Phosphate is determined by reaction with vanadomolybdate and the yellow colour evaluated at 410nm. Between 20 and lOOOmg kg-1 phosphorus in soil has been determined using this method. 

Tissue culture, more frequently used as cell culture, enables animal and plant cells to be cultured in large numbers by techniques comparable to those used in microbiology but, because of the fragile nature of the cells, does require special cultural conditions. The culture media used must supply all the essential factors for growth, such as a wide range of amino acids, nucleotides, enzyme co-factors as well as indeterminate factors that can only be supplied in special products, e.g. foetal bovine serum. The environmental conditions must be carefully controlled, particularly pH, and this is frequently maintained by culturing in a bicarbonate buffer system and a carbon dioxide saturated atmosphere. 

Analytical methods for ONOO related to the vascular system have been reviewed. Special attention is given to assays involving oxidation of dihydrorhodamine 123 (345) to yield the fluorescent product rhodamine 123 (346, equation 118), luminol (124) CL and nitrotyrosine formation. The reaction of peroxynitrite and carbon dioxide or bicarbonate... 

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