What is Sodium Hydroxide?
Sodium hydroxide, with the chemical formula NaOH, is commonly known as caustic soda, caustic soda, and caustic soda. It is a strong alkali with strong corrosivity, generally in the form of flakes or lumps. It forms alkaline solution and has deliquescent property. It is easy to absorb water vapor (deliquescent) and carbon dioxide (deterioration) in the air. Hydrochloric acid can be added to check for deterioration.
Synonym NaOH generally refers to sodium hydroxide
- Chinese name
- Sodium hydroxide
- English name
- Sodium hydroxide [1]
- nickname
- Caustic soda, caustic soda, caustic soda
- Chemical formula
- NaOH
- Molecular weight
- 39.996 [1]
- CAS Registry Number
- 1310-73-2
- EINECS registration number
- 215-185-5
- Melting point
- 318.4 (591 K)
- Boiling point
- 1390 (1663 K)
- Water soluble
- 109 g (20 ) (very soluble in water)
- Density
- 2.130 g / cm³
- Exterior
- White translucent flakes or granules
- Flash point
- 176-178
- Application
- Bleaching, papermaking, etc.
- Security description
- Corrosives, deliquescent
- Danger symbol
- 36 / 38-35-34
- Risk description
- Corrosive
- Dangerous Goods Transport Number
- UN 1824 8 / PG 2 [Liquid sodium hydroxide] UN1823 [Solid sodium hydroxide] [2]
- C 17 H 33- : 8-heptadecenyl. R-COOH is oleic acid.
- C 15 H 31- : n-pentadecyl. R-COOH is palmitic acid.
- C 17 H 35- : n-heptadecanyl. R-COOH is stearic acid.
- Sodium hydroxide, with the chemical formula NaOH, is commonly known as caustic soda, caustic soda, and caustic soda. It is a strong alkali with strong corrosivity, generally in the form of flakes or lumps, easily soluble in water (exothermic when dissolved in water) and It forms alkaline solution and has deliquescent property. It is easy to absorb water vapor (deliquescent) and carbon dioxide (deterioration) in the air. Hydrochloric acid can be added to check for deterioration.
- NaOH is one of the necessary chemicals in the chemical laboratory, and it is also one of the common chemicals. Pure products are colorless and transparent crystals. The density is 2.130g / cm³. Melting point 318.4 ° C. The boiling point is 1390 ° C. The industrial product contains a small amount of sodium chloride and sodium carbonate, and is a white opaque crystal. There are lumps, flakes, grains and rods. The formula is 39.997.
- Sodium hydroxide can be used as an alkaline cleaning agent in water treatment, soluble in ethanol and glycerol; insoluble in propanol and ether. Disproportionation with halogens such as chlorine, bromine and iodine. Neutralizes with acids to form salts and water.
Research history of sodium hydroxide
- Sodium hydroxide has long been known as an alkaline substance.
- In 1787, doctor Nicolas Leblanc (1762-1806) invented a suitable process for preparing sodium hydroxide from common salt and carried out mass production. [3]
- In 1887, Swedish chemist Arrhenius founded the theory of acid-base ionization (that is, the theory of aqueous solution acid-base). He proposed that acid is a substance in the aqueous solution where all cations generated by ionization are hydrogen ions, and the base is in the aqueous solution All anions produced by ionization are hydroxide ions. [4] From this, the basicity of sodium hydroxide is clearly defined.
Physical and chemical properties of sodium hydroxide
Physical properties of sodium hydroxide
- Sodium hydroxide is a white translucent crystalline solid. Its aqueous solution has an astringent and creamy feel. [5]
- Water absorption (deliquescent): Sodium hydroxide is prone to deliquescent in the air, so solid sodium hydroxide is often used as a desiccant. [6] But liquid sodium hydroxide does not absorb water.
- Solubility :
- It is very soluble in water and emits a lot of heat when dissolved. Soluble in ethanol and glycerin.
- The solubility of sodium hydroxide in water varies as follows:
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Sodium hydroxide chemical properties
- Alkaline
- Sodium hydroxide dissolved in water will completely dissociate into sodium ions and hydroxide ions, so it has the generality of alkali. [1]
- It can be acid-base neutralized with any protonic acid (also a metathesis reaction):
- NaOH + HCl = NaCl + HO
- 2NaOH + HSO = NaSO + 2HO
- NaOH + HNO = NaNO + HO
- Similarly, its solution can undergo metathesis reaction and coordination reaction with salt solution:
- NaOH + NHCl = NaCl + NH · HO
- 2NaOH + CuSO = Cu (OH) + NaSO
- 2NaOH + MgCl = 2NaCl + Mg (OH)
- ZnCl 2 + 4NaOH (excess) = Na 2 [Zn (OH) 4 ] + 2NaCl
- Sodium hydroxide is easily deteriorated into sodium carbonate (NaCO) in the air, because the air contains acid oxide carbon dioxide (CO):
- 2NaOH + CO = NaCO + HO This is also a manifestation of its alkalinity.
- If excessive carbon dioxide is continuously passed in, sodium bicarbonate (NaHCO) will be formed, commonly known as baking soda. The reaction equation is as follows:
- NaCO + CO + HO = 2NaHCO
- Similarly, sodium hydroxide can react with acidic oxides such as silicon dioxide (SiO) and sulfur dioxide (SO):
- 2NaOH + SiO = NaSiO + HO
- 2NaOH + SO (trace) = NaSO + HO
- NaOH + SO (excess) = NaHSO (the generated NaSO and water react with the excess SO to form NaHSO)
- Organic reaction
- In many organic reactions, sodium hydroxide also plays a similar role as a catalyst.
- Example of alkali-catalyzed alkylene oxide ring opening
- RCOOR '+ NaOH = RCOONa + R'OH [7]
- Can also catalyze many other reactions, such as alkylene oxide ring-opening, haloform reactions, etc .:
- I 2 + NaOH + R (CH 3 ) C = O R-COONa + CHI 3 (form iodoform)
- Sodium hydroxide can undergo nucleophilic substitution reactions with halogenated hydrocarbons, such as:
- CH 3 CH 2 Cl + NaOH CH 3 CH 2 OH + NaCl
- Elimination of halogenated hydrocarbons may also occur:
- CH 3 CH 2 Cl + NaOH CH 2 = CH 2 + NaCl + H 2 O
- Sodium hydroxide can decarboxylate carboxylic acids under strong heat, such as:
- R-COONa + NaOH RH + Na 2 CO 3 [8]
- Color response
- It can react with indicators:
- Sodium hydroxide solution turns red after dropping into phenolphthalein test solution
- The sodium hydroxide solution is alkaline, making the litmus test solution blue and the phenolphthalein test solution red.
- Other reactions
- Aluminum reacts with sodium hydroxide to form hydrogen. [9] In 1986, a tanker truck in the United Kingdom accidentally loaded a 25% sodium hydroxide aqueous solution by weight. The sodium hydroxide chemically changed with the aluminum on the tank wall, causing permanent damage to the tank due to internal pressure overload. The reaction equation is as follows:
- 2Al + 2NaOH + 6HO = 2Na [Al (OH) ] (sodium tetrahydroxyaluminate) + 3H [10]
- Note: Sodium tetrahydroxyaluminate can be considered as the product of the combination of sodium metaaluminate with 2 waters [10]
- Silicon also reacts with sodium hydroxide to generate hydrogen, such as:
- Si + 2NaOH + HO = NaSiO + 2H
- The preparation of aluminum hydroxide also involves the use of sodium hydroxide:
- 6NaOH + 2KAl (SO) = 2Al (OH) + KSO + 3NaSO
- Note: Al (OH) (aluminum hydroxide) is a colloidal coagulant commonly used to remove impurities in water. Because the hydroxides of transition metals are mostly insoluble in water and the surface area of aluminum hydroxide is large enough to adsorb small particles, the addition of alum (KAl (SO 4 ) 2 · 12H 2 O) in tap water can promote Precipitation in the form of hydroxide, and then simple filtration equipment can be used to complete the preliminary filtration of tap water.
- Aluminum hydroxide can be used to prepare alum (KAl (SO 4 ) 2 · 12H 2 O): dissolve aluminum hydroxide in sulfuric acid, then add metered potassium sulfate solution to heat the reaction, filter, concentrate, crystallize, centrifuge, dry To obtain a finished product of potassium aluminum sulfate.
- The detailed principle of water purification is that alum can ionize two metal ions in water: KAl (SO 4 ) 2 = K + + Al 3+ + 2SO 4 2- , and Al 3+ can easily generate colloidal aluminum hydroxide Al ( OH) 3 : Al 3+ + 3H 2 O Al (OH) 3 + 3H + . The aluminum hydroxide colloid has a strong adsorption capacity. It can adsorb impurities suspended in water and form a precipitate to make the water clear. [11]
Preparation method of sodium hydroxide
Sodium hydroxide laboratory method
- Sodium salt reacts with calcium oxide
- You can use some sodium bicarbonate (baking soda) and some calcium oxide (Quicklime). Put quicklime in water, and turn into lime slurry (calcium hydroxide solution, slaked lime) after the reaction. Add solid particles (concentrated solution) of sodium bicarbonate (or sodium carbonate) to the lime slurry to ensure the product sodium hydroxide The purity required to make lime slurry too. Reason: Refer to the solubility of calcium hydroxide and sodium carbonate. Stir to speed up the reaction. After it reacts for a while, let it stand for a while. With the precipitation of calcium carbonate, the supernatant is the sodium hydroxide solution. Pour it out carefully. (Remember not to put on filter paper when weighing after pouring out!)
- CaO + HO = Ca (OH)
- NaHCO + Ca (OH) = CaCO + NaOH + HO (recommended)
- Ca (OH) + NaCO = CaCO + 2NaOH [6] [2]
- Sodium reacts with water
- Take a piece of metallic sodium, wipe off the kerosene on the surface, scrape off the surface oxide layer, and place it in a beaker of water.
- 2Na + 2HO = 2NaOH + H
- Phenomenon: (floating, melting, swimming, ringing)
- Float: Sodium floats on water;
- Melt: Sodium melts into small balls;
- Swimming: Sodium moves upstream on the water surface because hydrogen is generated;
- Loud: Sodium sizzles because hydrogen is generated.
Industrial production method of sodium hydroxide
- Industrial production of caustic soda has three methods: causticizing method, electrolytic method and ion exchange membrane method.
- Causticization
- The soda ash and lime are respectively made into a soda ash solution and lime into lime milk. The causticizing reaction is performed at 99-101 ° C. The causticizing solution is clarified, evaporated and concentrated to more than 40% to obtain liquid caustic soda. The concentrated solution was further boiled and solidified to obtain a solid caustic soda product. The causticizing mud is washed with water, and the washing water is used for alkalizing. [12]
- Na 2 CO 3 + Ca (OH) 2 = 2NaOH + CaCO 3
- Diaphragm electrolysis
- After adding the original salt, add soda ash, caustic soda, and barium chloride refined preparations to remove impurities such as calcium, magnesium, and sulfate ions, and then add sodium polyacrylate or caustic bran in the clarification tank to accelerate the precipitation. After sand filtration, add hydrochloric acid And, the brine is sent to electrolysis after preheating, and the electrolytic solution is preheated, evaporated, salt-separated, and cooled to obtain liquid caustic soda, and further boiled to obtain a solid caustic soda product. The salt mud washing water is used for salting. [13]
- 2NaCl + 2H 2 O [Electrolysis] = 2NaOH + Cl 2 + H 2
- Ion exchange membrane method
- After the original salt is salted, the salt water is refined according to the traditional method. After the primary salt water is filtered through a microporous sintered carbon tube filter, it is further refined through a coupled ion exchange resin tower to make calcium and magnesium in the salt water. When the content drops below 0.002%, the secondary refined brine is electrolyzed to generate chlorine gas in the anode chamber. Na + in the brine in the anode chamber enters the cathode chamber and the OH of the cathode chamber through the ion membrane to generate sodium hydroxide. Hydrogen is generated. During the electrolysis process, an appropriate amount of high-purity hydrochloric acid is added to the anode chamber to neutralize the returned OH-, and the required pure water should be added to the cathode chamber. The concentration of high-purity caustic soda produced in the cathode chamber is 30% to 32% (mass), which can be directly used as a liquid alkali product or can be further concentrated to obtain a solid caustic soda product. [13]
- 2NaCl + 2HO = 2NaOH + H + Cl
Sodium hydroxide detection method
Laboratory determination of sodium hydroxide
- Method name: Sodium hydroxideDetermination of sodium hydroxide
- Methyl orange
- Application range: This method uses the titration method to determine the sodium hydroxide content.
- This method is suitable for sodium hydroxide.
- Experimental principle: Use the acid-base indicator to show different color characteristics when the pH of the solution is different. When the pH of the sample solution is adjusted to a specific value with acid, the amount and deterioration of sodium hydroxide in the sample are calculated by consuming the amount of acid. The amount.
- Reagent:
- 1. Water (new boiling and cooling);
- 2. Sulfuric acid titration solution (0.1mol / L);
- 3. Phenolphthalein indicator liquid;
- 4. Methyl orange indicator solution: take 0.1g of methyl orange, add 100mL of water to dissolve, that is, obtained.
- Equipment: acid burette, analytical balance, volumetric flask, Erlenmeyer flask, iron stand, pipette.
- Operation steps: After adding the appropriate amount of fresh boiling cold water for the test product to dissolve, let it cool, dilute it to the mark with water, shake well, take 25mL precisely, add 3 drops of phenolphthalein indicator solution, and use sulfuric acid titration solution (0.1mol / L) Titrate until the red color disappears, record the volume (mL) of the sulfuric acid titration solution (0.1mol / L) consumed, add 2 drops of methyl orange indicator solution, and continue to add the sulfuric acid titration solution (0.1mol / L) to a continuous orange-red color. Consume the volume (mL) of sulfuric acid titrant (0.1mol / L) twice before and after, calculate the alkali content (calculated as NaOH) in the test amount and consume the sulfuric acid titrant (0.1mol / L) after adding the methyl orange indicator solution ) Volume (mL), calculate the NaCO content in the test volume. [14]
- Note: "Precise weighing" means that the weighed weight should be accurate to one thousandth of the weighed weight. "Precision weighing" means that the accuracy of the measured volume should meet the accuracy of the pipette in the national standard Claim.
Sodium hydroxide deterioration inspection
- NaCO will be formed when NaOH deteriorates
- Chemical equation: 2NaOH + CO = NaCO + HO
- 1. If excessive dilute hydrochloric acid is added dropwise to the sample, sodium hydroxide deteriorates if bubbles are generated .
- Principle: 2HCl + NaCO = 2NaCl + CO + HO
- (The air contains a small amount of CO, and the open NaOH solution can react with CO to generate NaCO and HO to deteriorate; H + in HCl can react with CO 2 2- ions in NaCO to generate CO gas and HO. Bubbles produce this phenomenon to check for deterioration)
- Note: HCl will preferentially react with NaOH to generate NaCl and HO. Because NaOH is a strong base, NaCO is an alkaline solution in water.
- 2. Clarified lime water was added dropwise to the sample . If a white precipitate formed, the sodium hydroxide deteriorated.
- Principle: NaCO + Ca (OH) = CaCO + 2NaOH
- 3. Barium chloride is added to the sample. If white precipitate is formed, the sodium hydroxide deteriorates.
- Principle: NaCO + BaCl = BaCO + 2NaCl
- 4. Check for partial deterioration of sodium hydroxide [15] :
- Add excess BaCl or Ba (NO) 2 to complete precipitation, and prove that NaCO is produced. After the precipitate is completely stationary, take the supernatant in a test tube, add the colorless phenolphthalein solution dropwise, and the phenolphthalein turns red, which proves that NaOH.
- Note: Do not add NHCl dropwise, because NaCO becomes alkaline after dissolving in water because there will be OH¯ ions, and NH + combined with OH¯ will have an irritating odor. It is impossible to distinguish between original sodium hydroxide and carbonic acid. Caused by sodium.
- Add excess CaCl 2 to NaOH: 1. If there is a white precipitate, it means that NaOH is deteriorated; 2. Add colorless phenolphthalein, if the colorless phenolphthalein does not change color, it means complete deterioration. If the colorless phenolphthalein turns red, it indicates partial deterioration.
Application field of sodium hydroxide
- Sodium hydroxide ( NaOH ) is extremely versatile. Used in the production of paper, soap, dyes, rayon, metal smelting, petroleum refining, cotton fabric finishing, coal tar product purification, and food processing, wood processing and machinery industries.
Sodium hydroxide chemical experiment
- Can be used for chemical experiments. In addition to being used as a reagent, it can also be used as an alkaline desiccant because of its strong water absorption and deliquescent properties. [6] It can also absorb acid gases (such as in the experiment of sulfur burning in oxygen, sodium hydroxide solution can be put into a bottle to absorb toxic sulfur dioxide).
- Neutral and alkaline gases are mixed with CO , and NaOH can be used to remove impurities to generate NaCO (sodium carbonate) and HO (the generated NaCO is dissolved in HO ) :
- CO + 2NaOH = NaCO + HO; H 2 O + CO 2 + Na 2 CO 3 = 2NaHCO 3
Sodium hydroxide chemical industry
- Sodium hydroxide is widely used in the national economy, and many industrial sectors require sodium hydroxide. The sector that uses the most sodium hydroxide is chemical manufacturing, followed by paper manufacturing, aluminum smelting, tungsten smelting, rayon, rayon and soap manufacturing. In addition, in the production of dyes, plastics, pharmaceuticals and organic intermediates, the regeneration of old rubber, the production of sodium metal and water electrolysis, and the production of inorganic salts, borax, chromium salts, manganates, phosphates, etc. are also used A lot of caustic soda. At the same time, sodium hydroxide is one of the important raw materials for the production of polycarbonate, superabsorbent polymer, zeolite, epoxy resin, sodium phosphate, sodium sulfite and a large number of sodium salts.
- Production of detergents
- Soap: Making soap is the oldest and most widespread use of caustic soda.
- Sodium hydroxide has been used for traditional domestic purposes. To this day, the demand for caustic soda in soaps, soaps and other types of washing products still accounts for about 15% of caustic soda.
- The main component of fats and vegetable oils is triglycerides (triacylglycerols), whose alkaline hydrolysis equation is:
- (RCOO) 3 C 3 H 5 (grease) + 3NaOH = 3 (RCOONa) (higher fatty acid sodium) + C 3 H 8 O 3 (glycerin)
- This reaction is the principle of producing soap, hence the name saponification reaction.
- The R radical may be different, but the R-COONa produced can be used as soap. Common R-has:
- Detergent: Sodium hydroxide is used to produce various detergents, and even today's laundry powder (sodium dodecylbenzenesulfonate and other ingredients) is also made from a large amount of caustic soda. The excess fuming sulfuric acid is neutralized.
- papermaking
- Sodium hydroxide plays an important role in the paper industry. Due to its alkaline nature, it is used in the process of cooking and bleaching paper sheets.
- The raw material for papermaking is wood or grass plants. In addition to cellulose, these plants also contain a considerable amount of non-cellulose (lignin, gum, etc.). Adding a dilute sodium hydroxide solution can dissolve and separate non-cellulose components, thereby preparing pulp with cellulose as the main component. [16]
- Rayon and textile
- Man-made fibers, such as rayon, rayon, and rayon, are mostly viscose fibers. They are made from cellulose, sodium hydroxide, and carbon disulfide (CS 2 ) as viscose. .
- In the textile industry, sodium hydroxide is used for fiber treatment and dyeing, and for mercerizing cotton fibers. After the cotton fabric is treated with the caustic soda solution, it can remove the wax, oil, starch and other substances covering the cotton fabric, and at the same time, it can increase the mercerizing color of the fabric and make the dyeing more uniform. [16]
- Refined oil
- Petroleum products after washing with sulfuric acid also contain some acidic substances, which must be washed with sodium hydroxide solution and then washed with water to obtain refined products. [16]
Sodium hydroxide food industry
- China's "Sanitary Standards for the Use of Food Additives" (GB 2920-1996) stipulates that it can be used as a processing aid and used in an appropriate amount according to production needs.
- Sodium hydroxide can be widely used in the following production processes: container cleaning process; starch processing process; carboxymethyl cellulose preparation process; sodium glutamate manufacturing process. [17]
Sodium hydroxide water treatment
- Sodium hydroxide is widely used in water treatment. In wastewater treatment plants, sodium hydroxide can reduce the hardness of water through a neutralization reaction. In the industrial field, it is a regeneration agent for the regeneration of ion exchange resins. Sodium hydroxide is strongly alkaline and has relatively high solubility in water. Because sodium hydroxide has relatively high solubility in water, it is easy to measure the amount and can be conveniently used in various fields of water treatment.
- Sodium hydroxide is used in water treatment as follows: elimination of water hardness; adjustment of pH value of water; neutralization of wastewater; elimination of heavy metal ions in water by precipitation; regeneration of ion exchange resin.
Sodium hydroxide metallurgy
- Sodium hydroxide is used to treat bauxite. Alumina is contained in bauxite, which is the raw material for making aluminum. Alumina can be purified from the concentrate with sodium hydroxide.
- Reaction equation: Al 2 O 3 + 2NaOH + H 2 O = 2Na [Al (OH) 4 ] or Al 2 O 3 + 2NaOH = 2NaAlO 2 + H 2 O [12]
- Sodium hydroxide is also used to extract tungstate from tungstenite:
- 4FeWO 4 + 8NaOH + 2H 2 O + O 2 = 4Na 2 WO 4 + 4Fe (OH) 3
- Sodium hydroxide is also used in the production of zinc alloys and zinc ingots.
Sodium hydroxide safety measures
Occupational health limit for sodium hydroxide
- Chinese occupational health standard is MAC = 2mg / m 3 .
Sodium hydroxide health hazards
- Invasion route: inhalation, ingestion.
- Health hazard: The product is strongly irritating and corrosive. Dust or smoke can irritate the eyes and respiratory tract, corrode the nasal septum, direct contact between the skin and eyes and NaOH can cause burns, and misuse can cause digestive tract burns, mucosal erosion, bleeding and shock. [18]
- Decomposition products: May produce harmful toxic fumes.
Prevention and treatment of sodium hydroxide
- Isolate the leaking contaminated area and set warning signs around it. It is recommended that emergency handlers wear gas masks and chemical protective clothing. Don't directly contact the leakage, collect it in a dry and clean covered container with a clean shovel, add a small amount of NaOH to a large amount of water, adjust to neutral, and then put it into the waste water system. It can also be washed with a large amount of water, and the diluted washing water is put into the waste water system. If a large amount of leakage, collect and recycle or dispose of it after harmless. [18]
Sodium hydroxide safety sign
- Sodium hydroxide is a strongly alkaline substance, which is highly corrosive and requires the "corrosive item" mark. [1]
Sodium hydroxide protection
- Respiratory protection: Wear gas masks if necessary.
- Eye protection: Wear chemical safety protective glasses. Protective clothing: Wear work clothes (made of anticorrosive materials). Use with care, be careful not to spill it on clothing, nose and mouth. [1]
- Hand protection: Wear rubber gloves.
- Other: After work, shower and change clothes. Pay attention to personal hygiene.
First aid measures for sodium hydroxide
- Skin contact: Rinse with water for at least 15 minutes (dilute solution) / dry with a cloth (concentrated solution), and then wash with 5-10% magnesium sulfate or 3% boric acid solution and seek medical attention.
- Eye contact: Immediately lift the eyelids and rinse with running water or saline for at least 15 minutes. Or rinse with 3% boric acid solution (or dilute acetic acid). Seek medical attention.
- Inhalation: Quickly leave the scene to fresh air. If necessary, give artificial respiration. Seek medical attention.
- Ingestion: When eating a small amount by mistake, immediately use vinegar, 3 to 5% acetic acid or 5% dilute hydrochloric acid, a large amount of orange juice or lemon juice, etc .; give egg whites, milk or vegetable oil and seek medical treatment quickly, do not induce vomiting and gastric lavage. [1]
Sodium hydroxide storage and transportation
Sodium hydroxide storage method
- Solid sodium hydroxide is tightly sealed in 0.5 mm thick steel drums, and the net weight of each drum is not more than 100 kg; plastic bags or two-layer kraft paper bags are fully or middle-opened steel drums; threaded glass bottles, iron-cap glass Ordinary wooden boxes outside bottles, plastic bottles or metal barrels (tanks); threaded glass bottles, plastic bottles or tin plated steel barrels (tanks) are covered with grate boxes, fiberboard boxes or plywood boxes; tin plated steel barrels ( Cans), metal drums (cans), plastic bottles or corrugated cardboard boxes with metal hoses. The packaging container should be complete and sealed, with obvious corrosive items mark. [19]
- Sodium hydroxide is slightly corrosive to glass products, and both will generate sodium silicate, making the piston in the glass instrument stick to the instrument. Therefore, do not use glass stoppers when storing sodium hydroxide solution, otherwise the bottle cap may not be opened.
- If the glass container is filled with hot sodium hydroxide solution for a long time, the glass container may be damaged.
- (SiO in glass: 2NaOH + SiO = NaSiO + HO)
Sodium hydroxide transportation method
- For rail transport, steel drums can be transported in open carts. The package should be complete at the time of shipment and the loading should be secure. During transportation, ensure that the container does not leak, does not collapse, does not fall, is not damaged, and is protected from moisture and rain. If the packaging container is found to have rust, cracks, holes, melted water, etc., the packaging should be replaced immediately or shipped early. The damaged container can be repaired by soldering. It is strictly prohibited to mix and transport with flammable or combustible materials, acids, edible chemicals, etc. The transportation vehicle should be equipped with leakage emergency treatment equipment during transportation. [10]
Common misunderstandings of sodium hydroxide
- Myth 1 : Iron cannot react with sodium hydroxide
- Fact: Sodium hydroxide can react with iron powder and produce metallic sodium (or potassium) at high temperature under anhydrous conditions.
- (Guy Lussac, etc.) Mix iron filings with caustic potassium (KOH) and caustic soda (NaOH), respectively, and heat them in a sealed curved glass tube. As a result, the caustic, which melts at high temperatures, chemically reacts with the red-hot iron filings to produce potassium and sodium metals. This method is simple and economical, and can produce large amounts of potassium and sodium. [20]
- Therefore, when melting sodium hydroxide in the laboratory, nickel containers should be used instead of iron containers.
- Myth 2 : Sodium hydroxide is a strong base, but it has no bactericidal effect
- Fact: Sodium hydroxide can be used for disinfection in specific places [21] , and it is also the country's recommended disinfectant to destroy prions.
- Note: Moderate and high-risk items contaminated by high-risk tissues (brain, dura mater, pituitary, eye, spinal cord, etc.) of patients infected with or suspected to be infected with prions, can choose one of the following methods Bacteria, and the degree of sterilization gradually increases:
- a) Soak the used articles in 1mol L sodium hydroxide solution for 60min, then clean, disinfect and sterilize according to the method in WS310.2. The pressure steam sterilization should be 134 138 for 18min. Or 132 , 30min, or 121 , 60min;
- b) Use a washing and disinfecting machine (preferably a cleaning agent with a virucidal activity) or other safe methods to remove the visible pollutants after use, then soak in a 1mol L sodium hydroxide solution for 60min, and place it in Pressure steam sterilization at 121 ° C for 30min; then clean and sterilize according to general procedures [22]
- Myth 3 : Sodium does not react with sodium hydroxide
- Fact: Sodium hydroxide can react with metallic sodium and is a method of preparing sodium oxide. [twenty three]
- details as follows:
- Heating with a mixture of sodium hydroxide and sodium metal to prepare sodium oxide.
- The metal sodium should be slightly excessive in order to remove a small amount of water contained in sodium hydroxide.
- Mix granular NaOH with small pieces of metallic sodium and place into a nickel crucible. The nickel crucible is placed in a hard glass tube with a sealed bottom, and the upper part of the tube is connected to a vacuum pump and a long tube pressure gauge. The mixture started to react at 300-320 ° C, and the generated hydrogen was pumped out by a vacuum pump. The degree of vacuum was maintained at 399.96 to 533.288 Pa (30 to 40 mmHg column), and the remaining sodium was distilled off under reduced pressure. The product is a white powder, of which Na 2 O contains only 96%, and 2% NaOH and 2% Na 2 CO 3 impurities.
- Myth 4: Sodium hydroxide dissolves in boiling water to make the water boil
- Fact: Sodium hydroxide dissolves in water and releases heat, but it is not the cause of the water boiling.
- details as follows:
- Take three test tubes, pour 5 mL of distilled water into the test tubes, first preheat on the outer flame of the alcohol lamp, and then focus the heating until the water in the test tube evaporates; remove the test tube and add to the boiling water A little sodium chloride, ammonium nitrate, and broken porcelain pieces were observed to boil water again in the test tube.
- As everyone knows, the broken porcelain pieces are insoluble in water; when sodium chloride is dissolved in water, the temperature of the solution will not change significantly. When solid ammonium nitrate is dissolved in water, it absorbs heat. The temperature of the solution should be reduced. When freshly boiled water was added, the water was observed to boil again. Obviously, the "reboiling of water is caused by the release of heat when solid sodium hydroxide is dissolved in water" is lacking.
- When distilled water is heated, the lack of a bubble-forming core in the liquid can easily lead to the formation of a superheated liquid, which is a metastable state. When a solid is added to a superheated liquid, it will invade the air bubbles, providing a gasification center, so you will see the water boil again. [twenty four]