Bicarbonate neutralization

Note - Some products such as amino acid solutions and multiple electrolyte solutions containing dextrose will not be brought to near physiologic pH by the addition of sodium bicarbonate neutralizing additive solution. This is due to the relatively high buffer capacity of these fluids. 

Part of the North Branch of the Potomac River runs crystal clear through the scenic Appalachian Mountains, but it is lifeless—a victim of acid drainage from abandoned coal mines. As the river passes a paper mill and a wastewater treatment plant near Westemport, Maryland, the pH rises from an acidic, lethal value of 4.5 to a neutral value of 7.2, at which fish and plants thrive. This happy "accident comes about because calcium carbonate exiting the paper mill equilibrates with massive quantities of carbon dioxide from bacterial respiration at the sewage treatment plant. The resulting soluble bicarbonate neutralizes the acidic river and restores life downstream of the plant.1... 

A high amount of bicarbonate is constantly being produced in the body. Degradation of 100 g protein yields approximately 1 mol bicarbonate (= 61 g). Bicarbonate neutralization takes place via the urea cycle too, as the synthesis of 1 mol urea requires 2 mol bicarbonate. Besides the lungs and kidneys, the liver therefore also plays an important role in acid-base metabolism and is partly responsible for pH homoeostasis. 

Thus the bicarbonate buffer in the liver with its components CO2 and HC03 is also used for maintaining pH homoeostasis. The various cellular and subcellular compartments can only keep their own specific pH values constant provided the pH value of the extracellular space is not subject to major fluctuations. A constant balance between the formation and excretion of CO2 and HCOj must therefore be guaranteed. Bicarbonate neutralization takes place, energy-driven and irreversibly, in the urea cycle. In this context, HC03 is considered to be a relatively strong base, whereas NH4+ is regarded as a weak acid. 

CCK also stimulates the release of sodium bicarbonate and large amounts of fluid from cells of the pancreatic duct. These epithelial cells line the lumen of the duct. The bicarbonate neutralizes gastric acid entering the duodenum through the pylorus. The effect of CCK on the duct cells is described later in this chapter. 

Secretin enters the blo<>dstream and travels to the pancreas, where it stimulates the duct cells lo release bicarbonate and large volumes of fluid into the pancreatic duct The duct cells are located in the walls of the pancreatic duct. This duct leads from the acinar cells of the pancreas to the ampulla of Vater. The bicarbonate neutralizes the gastric acid entering the duodenum, providing an environment suitable for the functioning of enzymes and absorptive processes that re<]uire a neutral pH. 

Orally ingested sodium bicarbonate neutralizes gastric acid with the evolution of carbon dioxide and may cause stomach cramps and flatulence. 

Dialysis removes the formaldehyde, formic acid, and methanol that build up in the bloodstream. The bicarbonate neutralizes the acid produced and helps offset the resultant acidosis. The ethanol competitively binds with the alcohol dehydrogenase. This slows the dehydrogenation of the methanol and allows time for the kidneys to excrete it. 

As bases sodium bicarbonate, NaHCOs (pKa=6.37), sodium carbonate, Na2C03 (pKa.=10.25), sodium hydroxide, NaOH (pKa= 15.74) and sodium ethoxide, NaOCzHs (pKa=20.58) are used. It is assumed that sodium bicarbonate neutralizes carboxylic acids, sodium carbonate - carboxylic acids and lactones, sodium hydroxide - carboxylic acids, lactones and phenols, whereas sodium ethoxide will react with all oxygen species, even extremely weak acids (pKa< 20.58). fti practice Boehm titration is limited to the determination of carboxylic groups, lactones and phenols [192 197]. Sodium ethoxide is not used very often owing to the necessity of performing the experiment in nonaqueous media and oxygen-free conditions. One of the reasons why the sodium salts were chosen as bases is that they do not form precipitates after reaction with gaseous CO2 and their specific interactions with carbon surfaces are minimal [198]. 

If some condition causes the hydronium ion concentration to increase (i.e., the pH begins to decrease), the equUihrium above involving hydronium ion will shift to the left, according to LeGhatelier s principle, to relieve this stress and maintain the equilibrium. This, in turn, will cause the equilihrium in the first reaction to shift to the left to expel more carbon dioxide. Thus, bicarbonate neutralizes acid in the hlood buffering system. 

Table 14.2 lists some common bases. Sodium hydroxide and potassium hydroxide are found in most chemistry laboratories. They are also used in processing petroleum and cotton and in soap and plastic manufacturing. Sodium hydroxide is the active ingredient in products such as Drano that work to unclog drains. Sodium bicarbonate can be foimd in most homes as baking soda and is also an active ingredient in many antacids. When taken as an antacid, sodium bicarbonate neutralizes stomach acid (see Section 14.5), relieving heartburn and sour stomach. 

People often use sodium bicarbonate as an antacid to neutralize excess hydrochloric acid in an upset stomach. What mass of hydrochloric acid (in grams) can 2.5 g of sodium bicarbonate neutralize (Hint Begin by writing a balanced equation for the reaction between aqueous sodium bicarbonate and aqueous hydrochloric acid.)... 

The neutralization process, as mentioned above, is performed to stop the reaction of the acid on the skin. Neutralization is completed when there is no further foaming reaction on the skin. Before this process is initiated, the eyes can be protected by placing a damp 2 " x 2 " (5 cm ) gauze fersilon sponge on the patient s closed eyelids. In addition, after the bicarbonated neutralizer and water spray, a postpeel moisturizer and a cold mask or frozen... 

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