1310-73-2

A white solid. Corrosive to metals and tissue. Used in chemical manufacturing, petroleum refining, cleaning compounds, drain cleaners.

CAUSTIC SODA (Sodium hydroxide) is a strong base. Reacts rapidly and exothermically with acids, both organic and inorganic. Readily absorbs moisture from the air to give caustic semi-solids that attack aluminum and zinc with the evolution of flammable hydrogen gas. Catalyzes the polymerization of acetaldehyde and other polymerizable compounds; these reactions can occur violently, for example, acrolein polymerizes with extreme violence when put in contact with alkaline materials such as sodium hydroxide [Chem. Safety Data Sheet SD-85 1961]. Reacts with great violence with phosphorus pentaoxide when initiated by local heating [Mellor 8 Supp.3:406 1971]. Contact (as a drying agent) with tetrahydrofuran, which often contains peroxides, may be hazardous---explosions have occurred in such a use of the chemically similar potassium hydroxide [NSC Newsletter Chem. Soc. 1967]. Mixing with any of the following substances in a closed container caused the temperature and pressure to increase: glacial acetic acid, acetic anhydride, acrolein, chlorohydrin, chlorosulfonic acid, ethylene cyanohydrin, glyoxal, hydrochloric acid (36%), hydrofluoric acid (48.7%), nitric acid (70%), oleum, propiolactone, sulfuric acid (96%) [NFPA 1991]. Accidental contact between a caustic cleaning solution (probably containing sodium hydroxide) and Pentol caused a violent explosion. [MCA Case History 363(1964)]. Heating with a mixture of methyl alcohol and trichlorobenzene during an attempted synthesis led to a sudden increase in pressure and an explosion [MCA Guide for Safety Appendix 3 1972]. Hot and/or concentrated NaOH can cause hydroquinone to decompose exothermically at elevated temperature. (NFPA Pub. 491M, 1975, 385)

Soluble in water. Dissolution can liberate enough heat to cause steaming and spattering and ignite adjacent combustible material [Haz. Chem. Data 1966].

Corrosive to tissue in presence of mois- ture, strong irritant to tissue (eyes, skin, mucous membranes, and upper respiratory tract), poison by ingestion.

Strong corrosive action on contacted tissues. INHALATION: dust may cause damage to upper respiratory tract and lung itself, producing from mild nose irritation to pneumonitis. INGESTION: severe damage to mucous membranes; severe scar formation or perforation may occur. EYE CONTACT: produces severe damage.

NaOH is utilized to neutralize acids and make sodium salts in petroleum refining, viscose rayon; cellophane, plastic production; and in the reclamation of solutions of their salts. It is used in the manufacture of mercerized cotton, paper, explosives, and dyestuffs in metal cleaning; electrolytic extraction of zinc; tin plating; oxide coating; laundering, bleaching, dishwashing; and it is used in the chemical industries.

Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.

UN1823 NaOH, solid, Hazard class: 8; Labels: 8-Corrosive material. UN1824 NaOH, solution, Hazard class: 8; Labels: 8-Corrosive material

A strong base and a strong oxidizer. Violent reaction with acid. Incompatible with water; flammable liquids; organic halogens, nitromethane, and nitrocompounds, combustibles. Rapidly absorbs carbon dioxide and water from air. Contact with moisture or water may generate heat. Corrosive to metals. Contact with zinc, aluminum, tin and lead in the presence of moisture, forming explosive hydrogen gas. Attacks some forms of plastics, rubber or coatings.

Discharge into tank containing water, neutralize, then flush to sewer with water.

White orthorhombic crystals, produced in the form of pellets, lumps, sticks, beads, chips, flakes or solutions; hygroscopic; very corrosive; rapidly absorbs CO2 and water from the air; density 2.13 g/cm³; melts at 323°C; vaporizes at 1388°C; vapor pressure 1 torr at 739°C and 5 torr at 843°C; very soluble in water (110 g/100mL at room temperature), generating heat on dissolution; aqueous solutions highly alkaline, pH of 0.5% solution about 13 and 0.05% solution about 12; soluble in methanol, ethanol and glycerol (23.8 g/100 mL methanol and 13.9 g/100 mL ethanol at ambient temperatures.).

Sodium hydroxide is manufactured by electrolysis of brine using inert electrodes. Chlorine is evolved as a gas at the anode and hydrogen is evolved as a gas at the cathode. The removal of chloride and hydrogen ions leaves sodium and hydroxide ions in solution. The solution is dried to produce the solid sodium hydroxide.
A second method uses the Kellner–Solvay cell. Saturated sodium chloride solution is electrolyzed between a carbon anode and a flowing mercury cathode. In this case the sodium is produced at the cathode rather than the hydrogen because of the readiness of sodium to dissolve in the mercury. The sodium–mercury amalgam is then exposed to water and a sodium hydroxide solution is produced.

Sodium hydroxide is strongly alkaline and can react with acids to form salts and water.

Sodium hydroxide reacts with acidic oxides to form salt and water, so sodium hydroxide can be used to absorb acid gases in the laboratory or industrially.

Sodium hydroxide can react with aqueous solutions of many metal salts to form sodium salts and metal hydroxides

When sodium hydroxide and ammonia salt are heated together, it can release ammonia

Sodium hydroxide is highly corrosive, so that the glass bottles storing sodium hydroxide solutions must be rubber stoppers, and glass stoppers should not be used to prevent a chemical reaction from opening. Sodium hydroxide is an important industrial raw material, and can be produced by electrolysis of saline solution industrially

Sodium hydroxide and potassium hydroxide are not flammable as solids or aqueous solutions.

Sodium hydroxide is widely used in pharmaceutical formulations to adjust the pH of solutions. It can also be used to react with weak acids to form salts.

Caustic soda (NaOH) is regarded as the strongest alkaline pH regulator. Caustic soda is a very active substance and is highly corrosive. The bulk of caustic soda is manufactured by electrolysis of saturated brines (NaCl). Caustic soda has a very strong pHregulating capability (i.e. from pH 7 to pH 14) at a relatively low dosage compared to other alkaline substances. Commercially, caustic soda is available in anhydrous form, but in most mining applications the caustic soda is supplied as a 50% solution.
In the mineral processing industry, sodium hydroxide is mostly used for alkalinity control during the processing of non-metallic minerals. In base metal flotation, the use of sodium hydroxide is rare.

Sodium hydroxide is widely used in the pharmaceutical and food industries and is generally regarded as a nontoxic material at low concentrations. At high concentrations it is a corrosive irritant to the skin, eyes, and mucous membranes.
LD50 (mouse, IP): 0.04 g/kg
LD50 (rabbit, oral): 0.5 g/kg

Sodium hydroxide should be stored in an airtight nonmetallic container in a cool, dry place. When exposed to air, sodium hydroxide rapidly absorbs moisture and liquefies, but subsequently becomes solid again owing to absorption of carbon dioxide and formation of sodium carbonate.

splash goggles and impermeable gloves should be worn at all times when handling these substances to prevent eye and skin contact. Operations with metal hydroxide solutions that have the potential to create aerosols should be conducted in a fume hood to prevent exposure by inhalation. NaOH and KOH generate considerable heat when dissolved in water; when mixing with water, always add caustics slowly to the water and stir continuously. Never add water in limited quantities to solid hydroxides. Containers of hydroxides should be stored in a cool, dry location, separated from acids and incompatible substances.

Common impurities are water and sodium carbonate. Sodium hydroxide can be purified by dissolving 100g in 1L of pure EtOH, filtering the solution under vacuum through a fine sintered-glass disc to remove insoluble carbonates and halides. (This and subsequent operations should be performed in a dry, CO2-free box.) The solution is concentrated under vacuum, using mild heating, to give a thick slurry of the mono-alcoholate which is transferred to a coarse sintered-glass disc and evacuated free of mother liquor. After washing the crystals several times with purified alcohol to remove traces of water, they are dried in a vacuum, with mild heating, for about 30hours to decompose the alcoholate, leaving a fine white crystalline powder [Kelly & Snyder J Am Chem Soc 73 4114 1951]. CAUSTIC. Sodium hydroxide solutions (caustic), 14.77. Carbonate ion can be removed by passage through an anion-exchange column (such as Amberlite IRA-400; OH--form). The column should be freshly prepared from the chloride form by slow prior passage of sodium hydroxide solution until the effluent gives no test for chloride ions. After use, the column can be regenerated by washing with dilute HCl, then water. Similarly, other metal ions are removed when a 1M (or more dilute) NaOH solution is passed through a column of Dowex ion-exchange A-1 resin in its Na+-form. Alternatively, carbonate contamination can be reduced by rinsing sticks of NaOH (analytical reagent quality) rapidly with H2O, then dissolving in distilled H2O, or by preparing a concentrated aqueous solution of NaOH and drawing off the clear supernatant liquid. (Insoluble Na2CO3 is left behind.) Carbonate contamination can be reduced by adding a slight excess of concentrated BaCl2 or Ba(OH)2 to a NaOH solution, shaking well and allowing the BaCO3 precipitate to settle. If the presence of Ba in the solution is unacceptable, an electrolytic purification can be used. For example, sodium amalgam is prepared by the electrolysis of 3L of 30% NaOH with 500mL of pure mercury for cathode, and a platinum anode, passing 15 Faradays at 4Amps, in a thick-walled polyethylene bottle. The bottle is then fitted with inlet and outlet tubes, the spent solution being flushed out by CO2-free N2. The amalgam is then washed thoroughly with a large volume of deionised water (with the electrolysis current switched on to minimize loss of Na). Finally, a clean steel rod is placed in contact in the solution with the amalgam (to facilitate hydrogen evolution), reaction being allowed to proceed until a suitable concentration is reached, before being transferred to a storage vessel and diluted as required [Marsh & Stokes Aust J Chem 17 740 1964].

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (dental preparations; injections; inhalations; nasal, ophthalmic, oral, otic, rectal, topical, and vaginal preparations). Included in nonparenteral and parenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.