月: 2023年1月

What Is Antimony?

Antimony is a rare metal with a silvery-white luster.

Antimony has the element symbol Sb, atomic number 51, and CAS number 7440-36-0. It can be obtained from naturally occurring ores, and China is the main producer in the world.

Properties of Antimony

1. Physical Properties

Antimony has a melting point of 630°C, a boiling point of 1,635°C, and a relative density of 6.7. Like most metals, it is virtually insoluble in water and organic solvents but can be dissolved in royal water.

2. Other Characteristics

Antimony has the following characteristics

• It is brittle and can be pounded to powder.
• Its volume increases when it solidifies.
• Hardness increases when alloyed with copper, tin, lead, etc.
• Toxic and bactericidal.

Taking advantage of these characteristics, antimony is used in various fields.

Uses of Antimony

Antimony is used mainly in industrial products as a material for semiconductors, electrodes, and alloys, as well as in automobiles, office automation equipment, home appliances, and many other products.

1. Flame Retardants

Antimony is mainly used as a flame retardant in combination with halogen-based flame retardants, except for halogen-containing polymers, where antimony trioxide (SbO3), a flame retardant compound, is used. The flame retardant effect of antimony trioxide is due to the formation of halogenated antimony compounds that react with hydrogen and oxygen atoms and OH radicals to suppress fires. Antimony compounds are used in applications to create flame-retardant materials, such as in children’s clothing, toys, aircraft, and automobile seat covers, as well as in polyester resins added to fiberglass composite materials such as engine covers for light aircraft.

2. Alloying Materials

Antimony can form very useful alloys with lead, increasing its hardness and mechanical strength, so various amounts of antimony are used as an alloying metal in most applications involving lead. For example, it can be added to the electrodes of lead-acid batteries to improve plate strength and charging properties and is also used in batteries to improve battery performance. Antimony is used in antifriction alloys (such as Babbitt metals), bullets, electrical cable coatings, type alloys, solders, pewter, and low-hardness hardening alloys.

3. Other

Antimony is used as an additive in engine block casting, antifriction material in brakes, wiring cords, and rubber parts, to name a few automotive applications. Other applications include stabilizers and catalysts in polymer production, semiconductor materials, and emetics.

Other Information on Antimony

1. Antimony Manufacturing Process

The extraction of antimony from ores depends on the quality and composition of the ore, but most antimony is mined as sulfide (stibnite). Antimony can be isolated from crude antimony sulfide by reduction with iron (Sb₂S₃+3Fe→2Sb+3Fe). It can also be isolated from oxides by carbothermic reduction (2Sb₂O₃+3C→4Sb+3CO₂).

2. Regulatory Information

Antimony is not designated under the Poisonous and Deleterious Substances Control Law, but its powdered form is classified as a “Hazardous Substance, Class II, Metallic Powder” under the Fire Service Law. Antimony is designated as a “Class 1 Designated Chemical Substance (Article 2, Paragraph 2 of the Law)” under the Act on Confirmation, etc. of Release of Specific Chemical Substances and Promotion of Chemical Management (PRTR Law) and as a “Hazardous and Noxious Substance to be Labeled or Notified” under the Industrial Safety and Health Law.

3. Handling and Storage Precautions

Precautions for handling and storage are as follows

• Keep the container tightly closed and store it in a dry, cool, and dark place.
• Use only outdoors or in well-ventilated areas.
• Avoid contact with hot surfaces, sparks, and naked flames as there is a risk of ignition.
• Avoid mixing with oxidizers such as halogen, alkali permanganate, or metal powders due to the risk of fire or explosion.
• Avoid contact with acids due to the risk of toxic gas generation.
• Wear protective gloves and glasses when using.
• Wash hands thoroughly after handling.
• In case of skin contact, rinse immediately with water.
• In case of eye contact, rinse cautiously with water for several minutes.

What Is Arsine Gas?

Arsine gas is a hydrogen compound of arsenic with the chemical formula AsH₃.

It is also called hydrogen arsenide or arsenic hydride. Arsine gas is highly poisonous to humans, with an allowable time-weighted average concentration of 0.005 ppm.

When inhaled in large quantities by humans, it can affect the kidneys and blood, and in the worst case, cause death. Symptoms of arsine gas may be seen hours to days later and require medical follow-up.

Uses of Arsine Gas

Arsine gas is known as one of the semiconductor material gases used in the semiconductor manufacturing process. However, arsine gas is extremely toxic and can cause serious damage to the blood and kidneys. Therefore, contamination of the semiconductor manufacturing work environment by arsine gas has become a problem, and it is important to study optimal methods of quantifying arsine gas in the semiconductor manufacturing environment.

Arsine gas also produces arsenic when heated. This property can be used to detect trace amounts of arsenic. This method, called the Marsh test, was invented by James Marsh in 1836.

Properties of Arsine Gas

Arsine gas has a melting point of -117°C and a boiling point of -55°C. It exists as a colorless gas at room temperature and has a characteristic garlic odor.

In 100 g of water at 0°C, 0.0019 g of arsine gas is soluble. It is soluble in polar solvents and insoluble in organic solvents. The acid dissociation constant is pKa=25. Combustion yields water and arsenic trioxide (As₂O₃). It decomposes to arsenic and hydrogen by light, heat, and water.

The chemistry of arsine gas is predictable by the average of the corresponding pnictogen (PH₃, SbH₃, etc.). Arsine gas has reducing properties and reacts explosively with oxidants. It is flammable and should be handled with care. It reacts with aqueous silver nitrate solutions to liberate silver and has a standard redox potential of Eº = -0.225V. A high concentration of aqueous silver nitrate precipitates Ag₃As-3AgNO₃, a yellow compound salt containing silver arsenide.

Structure of Arsine Gas

Arsine gas is a compound of hydrogen and arsenic with a molecular weight of 77.95. Its density in gas is 4.93 g/L and in liquid form at -64°C is 1.640 g/mL.

The steric structure of arsine gas is similar to that of ammonia. ∠H-As-H is 91.8° and is a pyramidal molecule with three equivalent 1.519 Å As-H bonds. The hydrogen bond angles are smaller than those of ammonia and are close to right angles. Arsenic has an electronegativity of 2.0 and hydrogen has an electronegativity of 2.1. It is less polar than ammonia and does not form hydrogen bonds.

Other Information on Arsine Gas

1. Method of Synthesis of Arsine Gas

Arsine gas can be synthesized by adding zinc as a catalyst to a chemical containing arsenic and reacting it with dilute sulfuric acid. When arsine gas and hydrogen gas are burned and the flame touches a cold glass or porcelain dish, the single arsenic adheres to it, yielding a shiny arsenic mirror.

Arsine gas can also be produced by the reaction of calcium arsenide with dilute sulfuric acid. Decomposition of the pigment Scheele’s Green by bacteria or mold can produce arsine gas. 

2. Characteristics of Organic Arsine Gas

Compounds in which the hydrogen atom of hydrogen arsenide is replaced by a hydrocarbon or halogen are also collectively called arsine gas. The general formula for a series of derivatives is RR¹R²As. Each substituent represents an H or organic group. They generally have an unpleasant odor and are poisonous.

A specific example is methylarsine, whose chemical formula is CH₃AsH₂. Triphenylarsine is available as a ligand. Its chemical formula is (C₆H₅)₃As.

What Is Allyl Alcohol?

Allyl alcohol is an unsaturated alcohol with the simplest structure, represented by the structural formula CH₂=CHCH₂OH.

Other names include 2-propene-1-ol, propenyl alcohol, and 3-hydroxypropene. The unsaturated alcohol with the lowest molecular weight in its structural formula is vinyl alcohol (CH₂＝CHOH), but vinyl alcohol isomerizes to acetaldehyde (CH₃COH), which is a more stable structure, making substantial allyl alcohol the lowest molecular weight unsaturated alcohol.

Uses of Allyl Alcohol

Allyl alcohol is used in a variety of fields as a raw material for various synthetic applications. In the chemical field, it is useful as an intermediate in the synthesis of epichlorohydrin, allyl glycidyl ethers, and propanesultone.

It is also used as a raw material for diallyl phthalate resin, resin additives, and allyl compounds such as glycerol. It is also used as a raw material for pharmaceuticals, fragrances, agrochemicals, fungicides, and flame retardants.

Properties of Allyl Alcohol

Allyl alcohol is a clear, colorless liquid with a molecular weight of 58.08 and a strong pungent odor. It has a density of 0.854 g/cm³, a melting point of -129°C, a boiling point of 97°C, a flash point of 21°C, an ignition temperature of 443°C, and a refractive index of 1.4134.

It is extremely soluble in water, soluble in ethanol, chloroform, and ether, and flammable. Inhalation of allyl alcohol vapor has a strong effect on the eyes and nose, and is designated as a Class I Designated Chemical Substance under the Chemical Substances Control Law and as a toxic substance under the Poisonous and Deleterious Substances Control Law.

Because of its high flammability, it is classified as a Class 4 Hazardous Substance, Class 2 Petroleum Soluble in Water under the Fire Service Law, and its handling and storage quantity are restricted. In addition, it is designated as a flammable hazardous substance, a hazardous substance that should be labeled or notified by name, and a toxic substance under the Industrial Safety and Health Law.

Other Information on Allyl Alcohol

1. Manufacturing Process of Allyl Alcohol

Industrial methods include isomerization of propylene oxide and direct oxidation of propylene. There are several other synthetic methods, including the allyl chloride method, the acrolein method, the propylene oxide method, and the allyl acetate method.

Propylene Oxide Isomerization
CH₂CH(CH₃)O → CH₂＝CHCH₂OH

Propylene oxide is isomerized by heating in the presence of potassium aluminum sulfate to produce allyl alcohol.

Direct Oxidation of Propylene
CH₃CH=CH₂ + CH₃COOH + 1/2O₂ → CH₂= CHCH₂OCOCH₃ + H₂O
CH₂= CHCH₂OCOCH₃ ＋ H₂O → CH₂＝CHCH₂OH + CH₃COOH

Propylene, acetic acid, and oxygen react to form allyl alcohol. This reaction is one of the methods to directly synthesize allyl alcohol from propylene, and by optimizing the reaction conditions, allyl alcohol can be obtained in high yield.

Acid Catalyzed Oxidation
Propylene is oxidized in the presence of strong acids such as phosphoric acid and sulfuric acid to produce allyl alcohol, allyl aldehyde, and allylic acid. Allyl alcohol must be separated and purified by post-treatment.

Hydrolysis of Allyl Chloride
CH₂=CHCH₂Cl + H₂O → CH₂=CHCH₂OH + HCl

Allyl alcohol is obtained by hydrolysis of chloroaryl.

2. Precautions for Handling Allyl Alcohol

Allyl alcohol has a strong pungent odor and should be handled with care. It may also react with strong oxidizing agents, causing an explosive reaction, so adequate safety measures are essential when handling it.

Since it is irritating to skin and mucous membranes, appropriate protective equipment such as rubber gloves, protective glasses, and masks should be worn when handling. In addition, allyl alcohol dissolves well in water, so adequate ventilation is required when handling it. If it comes in contact with skin or mucous membranes, rinse immediately with running water and consult a physician.

The product is highly volatile and flammable. Due to its low flash point of 22°C, it is important to keep it away from fire and heat sources. Storage away from corrosive and oxidizing materials is also recommended.

What Is Acetone?

Acetone is a ketone of the simplest structure, an amphiphilic liquid that is both hydrophilic and hydrophobic.

It is also called dimethyl ketone or 2-propanone. Acetone is classified as a “Class 4 Hazardous Substance, Petroleum No. 1, Water Soluble Liquid” under the Fire Service Law, and is extremely flammable.

It is also classified under the Industrial Safety and Health Law as a “hazardous and noxious substance that should be labeled or notified” and requires the wearing of appropriate protective equipment when handled.

Uses of Acetone

Acetone dissolves a wide variety of organic compounds, and because it is highly volatile and dries easily at room temperature, it is used as a solvent for resins, rubber, fats, paints, dyes, adhesives, acetyl cellulose, nitrocellulose, and many other applications.

Another application that takes advantage of its property of dissolving organic compounds well is the removal of dirt from laboratory equipment. Nail polish remover is another application. Because of its high volatility, acetone is sometimes used to remove water from laboratory equipment after it has been cleaned with water.

Acetone can also be used as a raw material for synthesizing acetic anhydride, methyl methacrylate, bisphenol A, ascorbic acid (vitamin C), chloroform, iodoform, and sulfonal, as well as a stabilizer for acetylene gas.

Properties of Acetone

Acetone is a clear, colorless, volatile liquid with the molecular formula CH₃COCH₃ and molecular weight of 58.08. It is light, with a specific gravity of 0.791, and can be mixed with water, ethanol, and ether in any proportion. Acetone also has an ethereal odor and an anesthetic effect.

Acetone has a flash point of -21°C and will ignite at room temperature. Its melting point is -93.9°C, boiling point 56.1°C, and ignition point 465~560°C. Due to its high volatility, it is necessary to ventilate the room and be careful of fire when using it.

It has a high affinity for many substances, whether hydrophilic or hydrophobic and dissolves well. Plastics, jewelry, and synthetic fibers may be attacked or discolored if they adhere to surfaces, so care should be taken to protect them beforehand, and if they do adhere, wipe them off immediately.

In addition, when acetone is thermally decomposed at high temperatures, ketene and methane are formed.

Other Information on Acetone

What Is Acetamide?

Acetamide, an odorless white or light yellow solid (powder or crystals), is an organic compound with the chemical formula CH₃CONH₂.

Transitioning from solid to liquid at 81°C, acetamide serves as an excellent solvent for various organic and inorganic compounds. It finds extensive use as a solvent in organic synthesis and as a peroxide stabilizer. Given its suspected carcinogenic nature, handling acetamide necessitates suitable protective gear and a well-ventilated space.

Notable reactions involving acetamide include hydrolysis, yielding ammonia and acetic acid. It is soluble in water and ethanol, yet almost insoluble in diethyl ether.

Acetamide is designated under the Industrial Safety and Health Law as Hazardous and Noxious Substance to be Labeled and Hazardous and Noxious Substance to be Notified. Additionally, it is classified as a Class 2 Designated Chemical Substance, Class 2 – No. 1 under the PRTR Law.

Uses of Acetamide

Primarily, acetamide is employed as a solvent in the synthesis of organic reagents, encompassing a broad range of agents such as oxidizing and reducing agents, condensing and halogenating agents, protectants, chiral substances, and organometallic reagents.

While solid at ambient conditions, acetamide melts into a solvent above 81°C, capable of dissolving a diverse array of compounds, thereby facilitating various organic synthesis applications.

Beyond its solvent properties, acetamide functions as a stabilizer for peroxides, known for their instability and high reactivity.

Properties of Acetamide

Acetamide, also referred to as ethanamide or methane carboxamide, exhibits high solubility in water, methanol, ethanol, and chloroform but is insoluble in ether.

Chemical Formula	CH3CONH2
English Name	Acetamide
CAS No.	60-35-5
Molecular Weight	59.07 g/mol
Melting Point/Freezing Point	81°C
Boiling Point	222°C

Other Information on Acetamide

1. Hazardousness of Acetamide

As per the Industrial Safety and Health Law, acetamide is identified as both a Hazardous and Noxious Substance to be Labeled and Hazardous and Noxious Substance to be Notified. Under the PRTR Law, it is classified as Class 2 Designated Chemical Substance and Class 2 – No. 1.

Risks associated with acetamide include its potential as a carcinogen, eye irritant, and negative effects on fertility or fetal development. Contact with skin or eyes may cause redness and pain.

2. Precautions for Use of Acetamide

Utilizing acetamide demands thorough safety checks and the use of appropriate protective equipment in a well-ventilated area. It is advisable to wear protective gloves, clothing, safety glasses, and masks before handling. If contact occurs, wash the area with water and soap, seeking medical advice if irritation persists.

Moreover, acetamide can combust under high heat, releasing irritating and corrosive gases, necessitating temperature control during use.

3. Deliquescence

Acetamide’s high water solubility means it can absorb moisture from the air, which may compromise its efficacy as a solvent in organic synthesis. It is recommended to store acetamide in an inert gas-filled container in a humidity-controlled environment to maintain stability.

4. Disposal Method

Given its toxicity, acetamide should not be disposed of into sewage systems. Disposal should be managed by certified waste disposal contractors, as per local regulations.

What Is Ethyl Acetoacetate?

Figure 1. Basic Information on Ethyl Acetoacetate

Ethyl acetoacetate is the ethyl ester of acetoacetate, with the chemical formula C₆H₁₀O₃. Also known as ethyl 3-oxobutanoate, it is a colorless, flammable liquid with a characteristic fruity odor. It is classified as a Class 4 Hazardous Substance and a Class 3 Non-Water Soluble Liquid under the Fire Service Law.

The relatively stable carbanion produced by the action of a base on ethyl acetoacetate is often used in carbon-carbon bond formation reactions.

Uses of Ethyl Acetoacetate

Ethyl acetoacetate is more reactive than other esters and is used as a raw material for various organic syntheses. Examples include its use as an intermediate in the manufacture of compounds such as antipyretic analgesics, antimalarials, antibiotics, amino acids, and vitamin B.

It also has a fruity odor and is used as a food flavoring agent and in perfumes. Additionally, it can be used in lacquer paints, dye manufacturing, plastic manufacturing, and as an analytical reagent.

Properties of Ethyl Acetoacetate

Ethyl acetoacetate has a melting point of -45°C, a boiling point of 180.8°C, a flash point of 70°C, and a refractive index of 1.41937 at 20°C. It is soluble in water at 20°C, with 2.86 g dissolving in 100 mL of water. It is extremely soluble in ethanol and acetone.

The hydrogen atom on the methylene moiety at position 2 of ethyl acetoacetate is relatively acidic, with a pKa of 10.7 at 25°C.

Hydrolysis of ethyl acetoacetate with dilute acid or dilute alkali yields carbon dioxide and acetone. However, when reacted with a strong alkali, acetic acid is formed.

Structure of Ethyl Acetoacetate

Figure 2. Structure of Ethyl Acetoacetate

The empirical formula of ethyl acetoacetate is CH₃COCH₂COOC₂H₅. Its molecular weight is 130.14 g/mol, and its density at 25°C is 1.021 g/cm³.

Ethyl acetoacetate exhibits keto-enol tautomerism; at 33°C, the enol form constitutes 15% of the total.

The carbanion, the conjugate base of ethyl acetoacetate, is in resonance with the two enolate structures, allowing the negative charge to be delocalized and stabilized.

Other Information on Ethyl Acetoacetate

1. Synthesis of Ethyl Acetoacetate

Figure 3. Synthesis of Ethyl Acetoacetate

Ethyl acetoacetate is obtained by reacting ethyl acetate with metallic sodium or by condensation of ethyl acetate with sodium ethoxide, whose chemical formula is C₂H₅ONa. These reactions are known as Claisen condensation.

Industrially, ethyl acetoacetate is produced by treating diketene with ethanol.

2. Reaction of Ethyl Acetoacetate

Ethyl acetoacetate has an active methylene moiety, forming a relatively stable carbanion with a base. An activated methylene is a methylene group adjacent to two electron-withdrawing groups, such as a carbonyl group.

Compounds with highly acidic activated methylene groups include malonate esters, cyanoacetates, and acetylacetone, offering stability for carbon-carbon bond formation. Examples include acetoacetic ester synthesis and malonic ester synthesis.

Active methylene compounds like ethyl acetoacetate are also used in cross-coupling reactions and Michael addition reactions.

What Is Acetal?

Acetal is a generic term for a compound having a structure in which two identical carbons have an ether bond and is generally represented by the structural formula RCH(OR’)2. It is also used as an abbreviation for diacetyl of acetaldehyde, a typical compound with such a structure, i.e., 1,1-diethoxyethane.

The latter, 1,1-diethoxyethane, is a colorless volatile liquid and is classified as a flammable liquid, eye irritant, and specific target organ toxic (single exposure) in the GHS classification. In addition, it is designated as a hazardous and flammable substance under the Industrial Safety and Health Law and as a Class 4 Inflammable Liquid under the Fire Service Law.

Uses of Acetal

Acetals are commonly used as raw materials for resins and as a protective intermediate in organic synthesis. 1,1-Diethoxyethane, which has acetal as an abbreviation, is used as a raw material for organic solvents and synthetic fragrances.

Resins with acetal structure are generally called acetal resins or polyacetal and are produced by polymerization of the monomer formaldehyde. It is one of the most widely used polymers as an engineering plastic with excellent strength, modulus, and impact resistance.

What Is Butyl Acrylate?

Butyl acrylate, with the chemical formula C₄H₉O₂CCH=CH₂ and CAS number 141-32-2, is an ester of acrylic acid and n-butanol. This colorless to slightly pale-yellow flammable liquid has a strong ester odor and is also known as n-Butyl acrylate or BA.

Uses of Butyl Acrylate

Butyl acrylate is primarily utilized as a raw material for synthetic polymers, including both homopolymers and copolymers with other acrylates and esters. These polymers find applications in fiber treatments, adhesives, paints, acrylic resins and fibers, and acrylic rubber, due to their ability to adjust the glass transition temperature (Tg) and enhance flexibility.

1. Acrylic Rubber

Known for its excellent heat and oil resistance, acrylic rubber is used in automotive and industrial machinery for packing, seals, gaskets, and hoses.

2. Acrylic Resin

Acrylic resin’s exceptional transparency and workability make it a popular inorganic glass substitute for windows, light fixture covers, and various daily items.

3. Acrylic Paint

Chosen for its affordability and vibrant colors, acrylic paint is primarily used indoors due to its limited weather resistance.

4. Acrylic Adhesives

These adhesives are favored for their transparency, weather, and heat resistance, available in both two-component and one-component types, suitable for bonding plastics and metals.

5. Other Uses

Additional applications include paper and leather processing for enhanced resistance qualities and in cosmetics as binding agents to retain moisture.

Properties of Butyl Acrylate

With a melting point of -64 °C and boiling point of 145 °C, butyl acrylate is a liquid at room temperature, insoluble in water but soluble in organic solvents. Its density is 0.90 g/mL at 20°C. Classified as a Class 4 hazardous material, it requires specific storage and firefighting measures. Butyl acrylate polymerizes easily with initiators, necessitating inhibitors in commercial products to prevent uncontrolled reactions.

Other Information on Butyl Acrylate

Toxicity of Butyl Acrylate

Butyl acrylate poses various health hazards, including skin and eye irritation, potential for allergic reactions, and organ damage with acute or repeated exposure. It is also toxic to aquatic life. Protective measures, adequate ventilation, and proper disposal in compliance with regulations are crucial for safe handling.

What Is Sodium Oxalate?

Sodium oxalate is an inorganic compound with the chemical formula Na₂C₂O₄. It has a molecular weight of 134.0 g/mol, a density of 2.34 g/cm³, a melting point between 250℃ and 270℃, and a CAS number of 62-76-0. At room temperature and pressure, sodium oxalate appears as a colorless or white, odorless crystalline powder. It is primarily used as a reagent in titration experiments.

Under the Poisonous and Deleterious Substances Control Law, Sodium Oxalate is classified as a harmful substance.

Uses of Sodium Oxalate

Sodium oxalate is widely utilized as a standard reagent due to its high purity and stability, especially in redox titration experiments for determining hydrogen peroxide levels with potassium permanganate (KMnO₄) as the oxidizing agent. In these reactions, sodium oxalate acts as a reducing agent, resulting in carbon dioxide and water. The titration endpoint is indicated by a clear change in color due to the reaction dynamics.

To ensure accurate endpoint determination, the reaction mixture should be heated to about 60°C and stirred thoroughly, facilitating a faster reaction rate.

Other applications include its use as a dyeing aid, bleaching aid, plating bath additive, in leather tanning, as a reducing agent, and as a raw material in catalyst preparation and metal complex research.

Properties of Sodium Oxalate

Sodium oxalate, an ionic solid, is slightly soluble in water but insoluble in ethanol and other organic solvents. It is a salt formed from the reaction of oxalic acid, a weak acid, with sodium hydroxide, a strong base, making its aqueous solutions weakly basic.

Other Information on Sodium Oxalate

1. Manufacturing Process of Sodium Oxalate

Sodium oxalate can be synthesized by reacting oxalic acid with sodium hydroxide. Interestingly, plants produce oxalic acid during photosynthesis, but due to its toxicity, it is often found combined with sodium and calcium ions in various forms across different plant species. Spinach, for example, is notably high in sodium oxalate content.

2. Hazards of Sodium Oxalate

Sodium oxalate decomposes to produce carbon dioxide when heated, potentially reducing oxygen levels in enclosed spaces and causing symptoms like dizziness and nausea. Therefore, adequate ventilation is crucial when handling large quantities. Oxalic acid, a hydrolysis product, is irritating to skin and eyes, necessitating the use of protective gear such as eyewear, rubber gloves, and lab coats during handling. In case of skin contact, immediate rinsing with water is advised.

What Is Oxalic Acid?

Oxalic acid, known as ethanedioic acid in IUPAC nomenclature, is a dicarboxylic acid comprising two carbon atoms each bonded to a carboxyl group. This acid is commonly found in plants in its salt form and can be synthesized through various methods, including the reaction of sodium hydroxide with carbon monoxide to form sodium formate, which is then converted to calcium salts and reacted with sulfuric acid. Additionally, oxalic acid can be produced by oxidizing ethylene glycol or glyoxal with potassium dichromate.

Uses of Oxalic Acid

Oxalic acid has wide-ranging applications, serving as a raw material for dyes, a bleaching agent for wheat straw and cotton, and as a precursor for various chemicals.

1. Food Industry

In the food industry, it is utilized in producing glucose syrup and refining vegetable oils.

2. Medical Field

In pharmaceuticals, it aids in manufacturing persistent sulfa drugs, cerium oxalate, amino acid preparations, and alpha-keto acids.

3. Metal Processing Field

The metal processing industry employs oxalic acid for chemical polishing and pickling, vehicle and ship cleaning, radiator cleaning (for its rust removal and descaling properties), as a lubricant in cold-drawing stainless steel, in anodizing processes, and in refining rare earth metals. Furthermore, it is used as a standard for acid-alkali and redox titrations, thanks to the stability of its pure dihydrate crystals.

Properties of Oxalic Acid

Oxalic acid dissolves readily in cold water and ethanol, and to a lesser extent in hot water, but not in organic solvents like ether. Although often classified as a weak acid, it exhibits strong acidity in solution, demonstrating significant ionization.

Upon heating, oxalic acid anhydride decomposes, releasing carbon monoxide, carbon dioxide, and formic acid. Under certain conditions, such as exposure to sulfuric acid, the resultant formic acid further decomposes into water and carbon monoxide. Oxalic acid is hygroscopic, forming a dihydrate in moist air, which can be reverted to an anhydrous form by heating or using a desiccator.

Structure of Oxalic Acid

Oxalic acid, the simplest dicarboxylic acid, is denoted chemically as HOOC-COOH. It dissociates in water to form hydrogen oxalate ions H(COO)₂⁻ in the first step and oxalate ions (COO)₂²⁻ in the second step, with the structure of these ions being planar and featuring resonant carbon-oxygen bonds.

Other Information on Oxalic Acid

1. Compounds Containing Oxalic Acid Ion

Oxalic acid forms salts known as oxalates, which are ionic crystals, and hydrogenoxalates, which are acidic salts. While oxalates of alkali metals, aluminum, ammonium, and iron (III) are water-soluble, many oxalates of alkaline earth metals are not. Iron (III) oxalates decompose gradually in water, forming iron (II) oxalate, whereas silver oxalates decompose explosively upon heating.

2. Oxalic Acid in Nature

Abundantly present in plants, oxalic acid salts like sodium hydrogen oxalate occur in families such as Taxaceae, Catabaceae, and Acacaceae. Conversely, families like Araceae contain insoluble oxalate salts such as calcium oxalate, whose needle-like crystals can cause skin irritation upon contact.