Soda

SODA, a term used in everyday language to refer to both sodium bicarbonate salt (NaHCO3) and sodium carbonate (average) salt (Na2CO3). Sodium bicarbonate, sodium hydrogen carbonate, bicarbonate of soda, Natrium hydrocarbonicum (obsolete name Natrium bicarbonicum, Ph VI) NaHCO3; mol. wt. 84.0. A crystalline, dull white powder with a salty and then slightly alkaline taste, sp. gr. 2.22, soluble in (1:12) water at 15°. Soluble in glycerin (1:12), insoluble in alcohol. The aqueous solution has a weakly alkaline reaction (pH of a 10% solution - 8.4). The dry salt is stable. In the presence of moisture, in solution, even at ordinary temperature (on standing, on shaking), it loses CO2 and converts to sodium carbonate: 2NaHCO3 → Na2CO3 + H2O + CO2. Sodium carbonate, sodium carbonate, washing soda, Natrium carbonicum, Na2CO3.10H2O, Ph VI; mol. wt. 286.16. Sodium carbonate occurs in the form of: 1) a decahydrate, Na2CO3.10H2O, containing 37% Na2CO3; 2) a "dry" preparation, Natr. carbonicum siccum, corresponding approximately to the formula Na2CO3.2H2O and containing 74% Na2CO3, and 3) as "calcined soda," containing about 98-99% Na2CO3. ["Caustic soda" is sodium hydroxide (see Caustic alkalis)]. Sodium carbonate consists of large colorless transparent crystals (Na2CO3.10H2O), sp. gr. 1.446, or a white powder (Na2CO3.2H2O). The crystalline preparation effloresces very easily in the air; at 38°C it forms a monohydrate. The anhydrous salt, however, is hygroscopic. The decahydrate is soluble in water (63.2 in 100 at 15°) and glycerin (98 in 100). The aqueous solution has a strongly alkaline reaction due to hydrolysis (pH of a 10% solution = 11.46). Both preparations are obtained in the USSR by the Solvay process (Bereznikovsky chemical combine, Ukrkhimtrust). The action of alkali metal carbonates is determined by two factors: hydrolysis, which gives hydroxyl ions (OH'): Na2CO3 + H2O → NaHCO3 + NaOH, and the easy displacement of volatile carbon dioxide by other non-volatile and stronger acids, which leads to the neutralization of the latter. The sodium ion is a normal constituent of tissue fluids. On the proteins of protoplasm, carbonic alkalis act by softening and liquefying protein substances (peptization of gels by OH- ions), which forms the basis for speaking of the "dissolution" of protein substances by carbonic alkalis. The antiseptic action of dilute solutions of bicarbonate is weak. Hydroxyl ions generally act on cells excitatorily at moderate concentrations. The vital activity of simple organisms (infusoria, spermatozoa) increases. Carbonates are absorbed rapidly from the stomach and intestines, without significantly affecting the blood pH, but they increase the titratable alkalinity, i.e., they increase the concentration of bicarbonate. For therapeutic purposes, sodium bicarbonate is used predominantly. Carbonate is used rarely, exclusively externally, in the form of washings. By softening the superficial layer of the skin epithelium and emulsifying the lipids covering it, sodium carbonate has a detergent action. Internal use of bicarbonate occurs a) with the aim of changing the reaction of the contents of the stomach and small intestines, b) with regard to its effect on the acid-base system of the blood, and c) with a view to its chemical action on certain concretions, e.g., uric acid. Therapeutic use of NaHCO3: a) In acute and chronic dyspepsia accompanied by hyperacidity, in processes of fermentation in the stomach with the formation of lactic acid. b) In diabetes, for the prevention of diabetic coma, bicarbonate is prescribed up to 30-60 g pro die. When coma has begun, intravenous administration of a sterile 5% solution of NaHCO3 is practiced. c) In gout, it is prescribed in the form of carbonated waters. The action here is more likely to be attributed to the large amounts of liquid than to the influence of carbonic alkalis. d) The use of sodium bicarbonate in otorhinolaryngological practice is based on the dissolution and liquefaction of mucus by a solution of sodium bicarbonate. e) In gynecological practice, solutions of bicarbonate S. are used for increased acidity of vaginal mucus. f) For first and second degree burns, bicarbonate is applied in substance. g) In catarrhal conditions of the respiratory tract, bicarbonate sometimes brings benefit by promoting the dissolution of thick mucus accumulating in the pharynx; the excretion of NaHCO3 through the bronchi is very doubtful. The toxicological significance of carbonates is very small. Fatal cases from the use of bicarbonate are unknown. A 10% solution of carbonate S. can cause severe irritation on swallowing. Its action resembles dilute solutions of caustic alkalis. The antidote is the cautious use of a 1-2% solution of tartaric, citric or acetic acid.