Sodium bicarbonate

Description

Sodium bicarbonate (NaHCO3) is commonly referred to as baking soda by people outside of chemistry. It is amphoteric, meaning it can neutralize both acids and bases. The most common use of NaHCO3 is as a saturated aqueous solution for performing a basic wash during an aqueous workup.

Chemical properties

Sodium bicarbonate occurs as an odorless, white, crystalline powder with a saline, slightly alkaline taste. The crystal structure is monoclinic prisms. Grades with different particle sizes, from a fine powder to free-flowing uniform granules, are commercially available.

Physical properties

White crystalline powder or granules; monoclinic crystals; density 2.20 g/cm₃; decomposes around 50°C, begins to lose carbon dioxide; converts to sodium carbonate at 100°C; soluble in water, 10g/100 mL at 20°C; slowly decomposes to CO2 and Na2CO3 in aqueous solution at ambient temperature; decomposes to Na₂CO₃ in boiling water; aqueous solution slightly alkaline; pH of 0.1M solution at 25°C is about 8.3; insoluble in alcohol; decomposes in acids.

The Uses of Sodium bicarbonate

Sodium bicarbonate, used in the formof baking soda and baking powder, is the most common leavening agent. When baking soda,which is an alkaline substance, is added to a mix, it reacts with an acid ingredient to producecarbon dioxide. The reaction can be represented as: NaHCO3(s) + H+ → Na+(aq) + H2O(l) +CO2(g), where H+ is supplied by the acid. Baking soda is also used as a source of carbon dioxide for carbonatedbeverages and as a buffer.In addition to baking, baking soda has numerous household uses. It is used as a generalcleanser, a deodorizer, an antacid, a fire suppressant, and in personal products such as toothpaste.
The second largest use of sodium bicarbonate, accounting for approximately 25% of totalproduction, is as an agricultural feed supplement. In cattle it helps maintain rumen pH andaids fiber digestibility; for poultry it helps maintain electrolyte balance by providing sodiumin the diet, helps fowl tolerate heat, and improves eggshell quality.
Sodium bicarbonate is used in the chemical industry as a buff ering agent, a blowingagent, a catalyst, and a chemical feedstock.

Definition

Baking soda: A white solid formed either by passing an excess of carbon dioxide through sodium carbonate or hydroxide solution, or by precipitation when cold concentrated solutions of sodium chloride and ammonium hydrogencarbonate are mixed. Sodium hydrogencarbonate decomposes on heating to give sodium carbonate, carbon dioxide, and water. With dilute acids, it yields carbon dioxide. It is used as a constituent of baking powder, in effervescent beverages, and in fire extinguishers. Its aqueous solutions are alkaline as a result of salt hydrolysis. Sodium hydrogencarbonate forms monoclinic crystals.

Production Methods

Most sodium bicarbonate in the United States is made synthetically by the reaction of sodium carbonate solution (Na2CO3) with carbon dioxide: Na₂CO_3(aq) + H₂O_(l) + CO_2(g) → 2NaHCO_3(aq). It can also be produced using the Solvay process, which uses ammonia, carbon dioxide, and salt to produce sodium bicarbonate according to the following series of reactions: 2NH_3(g) + CO_2(g) + H₂O_(l) → (NH₄)₂CO_3(aq)
(NH₄)₂CO_3(aq) + CO_2(g) + H₂O_(l) → 2NH₃HCO_3(aq)
NH₄HCO_3(aq) + NaCl_(aq) → NaHCO_3(s) + NH₄Cl_(aq).

Production Methods

Sodium bicarbonate is manufactured either by passing carbon dioxide into a cold saturated solution of sodium carbonate, or by the ammonia–soda (Solvay) process, in which first ammonia and then carbon dioxide is passed into a sodium chloride solution to precipitate sodium bicarbonate while the more soluble ammonium chloride remains in solution.

Indications

Sodium bicarbonate is used for the treatment of metabolic acidosis which may occur in severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock or severe dehydration, extracorporeal circulation of blood, cardiac arrest and severe primary lactic acidosis. Also is indicated in severe diarrhea which is often accompanied by a significant loss of bicarbonate.
Further indicated in the treatment of certain drug intoxications, including barbiturates (where dissociation of the barbiturateprotein complex is desired), in poisoning by salicylates or methyl alcohol and in hemolytic reactions requiring alkalinization of the urine to diminish nephrotoxicity of blood pigments.

brand name

Neut (Abbott); Soda Mint (Lilly).

Air & Water Reactions

Stable in dry air, but slowly decomposes in moist air. Moderately water soluble. Decomposes slowly in water (accelerated by agitation) .

Reactivity Profile

Sodium bicarbonate reacts exothermically with acids to generate non-toxic carbon dioxide gas. Decomposes when heated. Incompatible with acids, acidic salts (dopamine hydrochloride, pentazocine lactate, many alkaloidal salts) aspirin and bismuth salicylate.

Fire Hazard

Literature sources indicate that Sodium bicarbonate is noncombustible.

Pharmaceutical Applications

Sodium bicarbonate is generally used in pharmaceutical formulations as a source of carbon dioxide in effervescent tablets and granules. It is also widely used to produce or maintain an alkaline pH in a preparation.
Additionally, sodium bicarbonate is used in solutions as a buffering agent for erythromycin, lidocaine, local anesthetic solutions, and total parenteral nutrition (TPN) solutions. In some parenteral formulations, e.g. niacin, sodium bicarbonate is used to produce a sodium salt of the active ingredient that has enhanced solubility. Sodium bicarbonate has also been used as a freeze-drying stabilizer and in toothpastes.
Therapeutically, sodium bicarbonate may be used as an antacid, and as a source of the bicarbonate anion in the treatment of metabolic acidosis. Sodium bicarbonate may also be used as a component of oral rehydration salts and as a source of bicarbonate in dialysis fluids; it has also been suggested as a means of preventing radiocontrast-induced nephrotoxicity.

Biological Activity

Commonly used laboratory reagent

Biochem/physiol Actions

Sodium bicarbonate can be used to treat salicylate poisoning.

Pharmacokinetics

Intravenous sodium bicarbonate therapy increases plasma bicarbonate, buffers excess hydrogen ion concentration, raises blood pH and reverses the clinical manifestations of acidosis.

Clinical Use

Metabolic acidosis
Alkalinisation of urine
Renoprotection against contrast media

Safety Profile

Low toxicity by ingestion. An experimental teratogen. A nuisance dust. Human systemic effects: changes in potassium levels, increased urine volume, metabolic acidosis, nausea or vomiting, respiratory changes, sodium level changes. Mutation data reported.

Safety

Sodium bicarbonate is used in a number of pharmaceutical formulations including injections and ophthalmic, otic, topical, and oral preparations.
Sodium bicarbonate is metabolized to the sodium cation, which is eliminated from the body by renal excretion, and the bicarbonate anion, which becomes part of the body’s bicarbonate store. Any carbon dioxide formed is eliminated via the lungs. Administration of excessive amounts of sodium bicarbonate may thus disturb the body’s electrolyte balance, leading to metabolic alkalosis or possibly sodium overload with potentially serious consequences. The amount of sodium present in antacids and effervescent formulations has been sufficient to exacerbate chronic heart failure, especially in elderly patients.
Orally ingested sodium bicarbonate neutralizes gastric acid with the evolution of carbon dioxide and may cause stomach cramps and flatulence.
When used as an excipient, sodium bicarbonate is generally regarded as an essentially nontoxic and nonirritant material.
LD50 (mouse, oral): 3.36 g/kg
LD50 (rat, oral): 4.22 g/kg

Veterinary Drugs and Treatments

Sodium bicarbonate is indicated to treat metabolic acidosis and alkalinize the urine. It is also used as adjunctive therapy in treating hypercalcemic or hyperkalemia crises.

Drug interactions

Potentially hazardous interactions with other drugs
Increases lithium excretion.

Metabolism

Oral bicarbonate, such as sodium bicarbonate, neutralises gastric acid with the production of carbon dioxide. Bicarbonate not involved in that reaction is absorbed and in the absence of a deficit of bicarbonate in the plasma, bicarbonate ions are excreted in the urine, which is rendered alkaline, and there is an accompanying diuresis.

Storage

Sodium bicarbonate is stable in dry air but slowly decomposes in moist air and should therefore be stored in a well-closed container in a cool, dry place.

Safety

Sodium bicarbonate is likely safe when used appropriately, short-term. Over-the-counter antacid products containing sodium bicarbonate are considered safe and effective by the US FDA. Taking sodium bicarbonate in very high doses is possibly unsafe. It is also possibly unsafe to take sodium bicarbonate that it is not fully dissolved into a solution. Stomach rupture and serious changes in electrolyte levels have occurred.

Purification Methods

Crystallise sodium bicarbonate from hot water (6mL/g). The solid should not be heated above 40℃ due to the formation of carbonate.

Incompatibilities

Sodium bicarbonate reacts with acids, acidic salts, and many alkaloidal salts, with the evolution of carbon dioxide. Sodium bicarbonate can also intensify the darkening of salicylates. In powder mixtures, atmospheric moisture or water of crystallization from another ingredient is sufficient for sodium bicarbonate to react with compounds such as boric acid or alum. In liquid mixtures containing bismuth subnitrate, sodium bicarbonate reacts with the acid formed by hydrolysis of the bismuth salt.
In solution, sodium bicarbonate has been reported to be incompatible with many drug substances such as ciprofloxacin, amiodarone, nicardipine, and levofloxacin.

Regulatory Status

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (injections; ophthalmic preparations; oral capsules, solutions, and tablets). Included in parenteral (intravenous infusions and injections) and nonparenteral medicines (chewing gums; ear drops; eye lotions; oral capsules, chewable tablets, effervescent powders, effervescent tablets, granules, soluble tablets, orodispersible tablets, and tablets; suppositories and suspensions) licensed in the UK.