月: 2023年1月

What Is Gallic Acid?

Gallic acid, an organic compound with the molecular formula C₇H₆O₅, belongs to the class of aromatic hydroxycarboxylic acids. Known also as 3,4,5-trihydroxybenzoic acid, it is identified by the CAS registration number 149-91-7.

This compound features a molecular weight of 170.12, melts at 250°C, and forms colorless columnar crystals at room temperature. It has a density of 1.7 g/mL, an acid dissociation constant (pKa) for COOH of 4.5 and for OH of 10, and a solubility in water of 1.1 g/100mL at 20℃. Gallic acid is hygroscopic, forming a monohydrate that loses its crystalline water around 120°C.

Uses of Gallic Acid

Gallic acid is highly valued for its strong reducing power, making it a popular antioxidant in foods, cosmetics, and feed. Its alkaline solutions serve as reducing agents and photo developers. Additionally, it finds application in the production of tannins, blue ink, dyes, culture engineering reagents, plant growth regulators, and as a growth inhibitor.

Its derivatives, including propyl and isoamyl gallic acid esters, are utilized as antioxidants for fats and oils, while epigallocatechin gallate, a type of catechin, exemplifies its use in the pharmaceutical industry as astringents and for hemostatic purposes.

Properties of Gallic Acid

In water, gallic acid forms an alkaline solution with strong reducing properties, readily oxidized by air. Catalytic hydrogenation of gallic acid yields cyclohexane ring derivatives. Heating induces decarboxylation, producing pyrogallol, a valuable reagent in organic synthesis, photography, and dyeing.

Gallic acid is hygroscopic; its monohydrate is stable up to its melting point, where it decomposes into pyrogallol and carbon dioxide.

Types of Gallic Acid

Gallic acid is available as a reagent for R&D and industrial chemical use, in quantities ranging from 10 g to 25 kg. These reagents, including the stable monohydrate, are stored at room temperature and cater to a broad range of industrial applications.

Other Information on Gallic Acid

1. Biosynthesis of Gallic Acid

Gallic acid occurs naturally in many plants, including the Japanese knotweed and the Middle Eastern beech and oak, serving as the backbone of hydrolysable tannins. Its biosynthesis involves the cyclization of 3,5-dihydroshikimic acid, produced from 3-dehydroshikimic acid by shikimic acid dehydrogenase.

2. Ester Derivatives of Gallic Acid

Numerous natural and synthetic ester derivatives of gallic acid are known, such as epigallocatechin gallic acid from tea. The enzyme gallic acid-1-beta-glycosyltransferase facilitates the glycosylation of gallic acid, illustrating its biochemical significance.

What Is Sodium Hydride?

Sodium hydride (NaH) is a gray crystalline powder known for its strong reducing properties, composed of sodium ions and hydride ions. It forms an ionic lattice and has notable applications due to its reactivity with acids, alkalis, and its ability to reduce various compounds.

Structure of Sodium Hydride

It exhibits a cubic NaCl crystal structure. An unusual variant, “inverse sodium hydride,” involves electron transfer from hydrogen to sodium, encapsulated by adamanzan to protect H⁺ from interaction with Na^–.

Properties of Sodium Hydride

With a melting point of 800°C and a density of 1.39 g/cm³, sodium hydride is insoluble in most solvents and reacts explosively with water. It’s stable in dry air but can ignite spontaneously in moist conditions.

Uses of Sodium Hydride

As a base and reducing agent in organic chemistry, sodium hydride facilitates various condensation and reduction reactions. It’s also explored for hydrogen storage in fuel cells and other applications like sugar engineering and metal surface treatment.

Manufacturing and Handling

Produced by dispersing in oil or reacting metallic sodium with hydrogen, it’s available commercially in mineral oil dispersion. Classified for careful handling due to its spontaneous ignition in contact with water, it requires stringent storage and safety measures.

Regulatory and Safety Information

While not designated under some laws, it’s considered a spontaneously ignitable substance, requiring protective gear during handling and specific precautions to avoid moisture exposure and ensure safe storage.

What Is Iron Hydroxide?

Iron hydroxide refers to hydroxides of iron and is classified into iron(II) hydroxide (Fe(OH)₂) and iron(III) hydroxide (Fe(OH)₃) based on the oxidation state of iron.

Iron Hydroxide (II)

Iron(II) hydroxide, or ferrous hydroxide, is an inorganic compound with the formula Fe(OH)₂. It forms as a white solid but readily oxidizes in the presence of oxygen to form a light green compound commonly known as “green rust,” seen on water taps. Upon heating in the air, it transforms into iron(III) oxide.

Iron Hydroxide (III)

Iron(III) hydroxide, or ferric hydroxide, has the formula Fe(OH)₃. However, the compound often found is iron hydroxide(III) oxide hydrate, with a composition of FeO(OH)-H₂O. This compound forms as a reddish-brown solid and occurs naturally in various ores like goethite, akaganeite, lepidocrocite, and limonite, or as the familiar red rust. It can form colloidal particles in alkaline solutions.

Iron Hydroxide Manufacturing Process

Iron(II) hydroxide can be prepared by reacting an aqueous solution of iron(II) sulfate with sodium hydroxide, resulting in the precipitation of Fe(OH)₂.

Iron(III) hydroxide is typically precipitated by adjusting the pH of an aqueous iron(III) salt solution. For example, it can be obtained by reacting ferric chloride or ferric nitrate with sodium hydroxide. Iron(III) hydroxide can also be prepared by oxidizing iron(II) hydroxide with hydrogen peroxide in an acidic environment.

Uses of Iron Hydroxide

Iron Hydroxide (II)

Iron(II) hydroxide is used in the manufacturing of enamels, catalysts, heat-absorbing glass, water quality improvement agents, and in the negative electrodes of nickel-iron batteries.

Iron Hydroxide (III)

Iron(III) hydroxide serves as a pigment in paints, inks, paper, rubber, and plastics, and as an abrasive for glass, precious metals, and diamonds. Its high-purity form is used in semiconductors, magnetic tapes, and magnets. It is FDA-approved for cosmetics, including some tattoo inks, and is utilized for lead removal, as a phosphate binder, and in water quality improvement.

What Is Lithium Hydroxide?

Lithium hydroxide (LiOH) is a hygroscopic white solid, soluble in water, forming a strongly alkaline solution. Available in monohydrate or anhydride forms, it’s regulated as a hazardous and toxic substance, requiring careful handling due to its corrosive properties.

Uses of Lithium Hydroxide

Its ability to absorb carbon dioxide makes it essential in space shuttles for air purification. In the battery industry, it serves as a key raw material for high-nickel cathode active materials in lithium-ion batteries, supporting the demand for renewable energy storage and electric vehicles. Additionally, it’s used in photographic solutions, as a stabilizer in grease, and as a food additive and pharmaceutical component.

Properties of Lithium Hydroxide

This white, odorless solid has a molecular weight of 23.95 and varies in density between its anhydrous and monohydrate forms. It is soluble in water, slightly soluble in alcohols, and decomposes at 924°C, releasing toxic fumes. It reacts violently with acids and corrodes metals like aluminum and zinc due to its strong alkalinity.

Other Information on Lithium Hydroxide

Production Methods

Lithium hydroxide is produced through:

1. Pulverization of Ore: Extracting lithium sulfate and lithium carbonate from ores, followed by impurity removal and precipitation of lithium as carbonate.

2. Reaction with Slaked Lime: Heating lithium carbonate with slaked lime to precipitate calcium carbonate and produce a lithium hydroxide solution, which is then concentrated and cooled to yield lithium hydroxide monohydrate.

3. Electrolysis: Purifying lithium sulfate solution for electrolysis, where lithium ions react with hydroxide ions generated at the cathode to form lithium hydroxide.

These processes highlight the careful and complex methods required to produce lithium hydroxide for its various important applications.

What Is Magnesium Hydroxide?

Magnesium hydroxide, with the chemical formula Mg(OH)₂, is found in minerals like bluestone and brucite, presenting as a white powder in industrial products. Due to its strong alkalinity and reaction with carbon dioxide to form barium carbonate, it is identified as a highly toxic substance requiring careful handling.

Uses of Magnesium Hydroxide

Its applications are diverse, including:

1. Environmental Applications

Used in flue gas desulfurization and as a neutralizer in wastewater treatment, it constitutes a significant demand in environmental management.

2. Flame Retardants

Added to plastics and building materials, it acts as an eco-friendly flame retardant.

3. Food and Pharmaceuticals

Recognized as safe for human consumption, it serves as a food additive, antacid, and laxative, leveraging its properties to neutralize stomach acid and stimulate intestinal motility.

Properties of Magnesium Hydroxide

This compound has a molecular weight of 58.34, a specific gravity of 2.39, and is practically insoluble in water. It reacts with weak acid solutions and ammonium salt solutions, with its aqueous solutions being alkaline. Magnesium hydroxide also absorbs CO₂ to form hydroxycarbonates and decomposes endothermically between 330-430°C, a trait utilized in flame retardancy.

Other Information on Magnesium Hydroxide

Production Methods

Three primary methods include:

1. Pulverization Method: Directly pulverizing bluesite, a natural ore, which is cost-effective but may lead to variable purity levels.

2. Alkaline Precipitation Method: Precipitating magnesium hydroxide from seawater or bittern by adding an alkali, often slaked lime, to form a low-cost and non-toxic byproduct.

3. Hydration Method: Reacting magnesia with hot water, an approach favored in regions with abundant magnesite resources.

Each method offers distinct advantages in terms of cost, purity, and environmental impact, making magnesium hydroxide a versatile compound in various industries.

What Is Barium Hydroxide?

Barium hydroxide, a basic inorganic compound of barium, primarily exists as a monohydrate (92-95%) in its dry form and as colorless octahydrate crystals in aqueous solution. Known as baryta water when dissolved, it is strongly alkaline and can react with carbon dioxide in the air to form barium carbonate. Due to its high toxicity, similar to other soluble barium compounds, it is regulated as a deleterious substance.

Uses of Barium Hydroxide

Its applications span from glass manufacturing, oil refining, and water softening to sugar manufacturing, producing various barium compounds, and organic synthesis. Barium hydroxide is also utilized in the saponification of fats and oils, as a stabilizer for grease and vinyl chloride, and as an analytical reagent in laboratories for titrations and carbon dioxide determination. It’s used for creating catalysts, lubricant additives, pigments, plating reagents, and for melting silicates.

Properties of Barium Hydroxide

This white crystalline compound is characterized by its ease of solubility in water and methanol, with a melting point of 408°C for the anhydride, 78°C for the octahydrate, and decomposition at 780°C. It appears granular or powdery, with a molecular weight of 171.34 and the chemical formula Ba(OH)₂. The anhydride has a monoclinic crystal structure, while the octahydrate is tetragonal. The densities for the anhydride, monohydrate, and octahydrate are 4.495 g/cm³ and 3.74 g/cm³, respectively.

Other Information on Barium Hydroxide

1. Synthesis Methods

Barium hydroxide is produced through the hydration of barium oxide, yielding octahydrate upon recrystallization and monohydrate when heated in air. Anhydride formation occurs at 100°C under reduced pressure. The reaction of barium nitrate with sodium hydroxide also produces barium hydroxide octahydrate.

2. Titration Applications

Used for titrating weak and organic acids in analytical chemistry, barium hydroxide’s solution clarity is due to its lack of carbonate, allowing for accurate endpoint determination in titrations with phenolphthalein or thymolphthalein as indicators.

3. Decomposition Reactions

As a strong base, it is employed in organic synthesis for ester and nitrile hydrolysis, including selective hydrolysis in specific organic compounds, and neutralizing acidic spills.

4. Synthetic Reactions

Barium hydroxide facilitates the synthesis of cyclopentanone, diacetone alcohol, and D(-)-gulonic acid γ-lactone, showcasing its versatility in chemical reactions.

What Is Nickel Hydroxide?

Nickel hydroxide, represented by various oxidation states, is most commonly found as nickel hydroxide (II). Due to its classification under multiple safety and health regulations, handling nickel hydroxide requires careful precautions.

Uses of Nickel Hydroxide

Nickel hydroxide (II) is crucial in rechargeable batteries, such as nickel-metal hydride, nickel-cadmium, and lithium-ion batteries, enhancing the performance of devices like cell phones and hybrid vehicles. It’s also used in surface treatment chemicals and plating, and as a catalyst.

Properties of Nickel Hydroxide

1. Nickel Hydroxide (I)

A dark blue precipitate, nickel hydroxide (I) is nearly water-insoluble and decomposes when exposed to moisture. It reacts with alkali sulfides and cyanides to form nickel (I) compounds.

2. Nickel Hydroxide (II)

This form is insoluble in water and alkaline solutions but dissolves in dilute acids, potassium cyanide, and ammonia.

3. Nickel Hydroxide (III)

With a density of 4.84 g/cm³ and a melting point of 600°C, nickel hydroxide (III) is often associated with black nickel oxide (Ni₂O₃).

Structure of Nickel Hydroxide

1. Nickel Hydroxide (I)

With the formula NiOH, it has a molar mass of 75.70 and is a monovalent nickel compound.

2. Nickel Hydroxide (II)

A light green crystal with the formula Ni(OH)₂, it has a hexagonal cadmium hydroxide-type crystal structure and a density of 4.15 g/cm³.

3. Nickel Hydroxide (III)

Often considered an indeterminate nickel oxide, Ni₂O₃ is a trivalent nickel hydroxide with a molar mass of 165.39.

Other Information on Nickel Hydroxide

1. Synthesis of Nickel Hydroxide (II)

Formed by reacting alkali hydroxide with a nickel (II) salt solution, it can also be precipitated from a hexa-ammonium nickel (II) complex, yielding Ni(OH)₂・1.5H₂O, which becomes anhydrous in vacuum.

2. Reaction of Nickel Hydroxide (II)

Upon heating to 230°C, it dehydrates to nickel (II) oxide. While resistant to oxidation by air or hydrogen peroxide, it is oxidized by ozone to nickel hydroxide (III).

What Is Sodium Hydroxide?

Sodium hydroxide (NaOH), an odorless, white monoclinic crystal, is a potent alkaline material in various industrial processes. Due to its classification as a deleterious substance under regulatory laws, handling it requires strict safety measures.

Uses of Sodium Hydroxide

Applications of sodium hydroxide span diverse sectors:

1. Detergents

It’s crucial in soap making for its saponifying effect and is used in kitchen detergents for oil removal.

2. Paper and Textile Industry

NaOH treats wood and plant fibers for pulp production and paper smoothing. It also processes cotton and hemp for enhanced flexibility and luster in textiles.

3. Industrial Applications

As a raw material, it facilitates ester hydrolysis, alkaline oxidation, and aromatic compound hydroxylation. It’s also employed in the electronics sector for silicon wafer etching and surface modification.

Additionally, NaOH finds use in food additives, dye production, agricultural chemicals, pharmaceuticals, as an analytical reagent, desiccant, and carbon dioxide absorbent.

Properties of Sodium Hydroxide

Sodium hydroxide, or caustic soda, is highly soluble in water, generating significant heat upon dissolution. It’s deliquescent, absorbing atmospheric moisture, and dissolves in ethanol and glycerin but not in ether or acetone. Its strong alkalinity can dissolve skin proteins upon contact, emphasizing the need for careful handling and storage in dry, airtight containers.

Other Information on Sodium Hydroxide

How Sodium Hydroxide Is Produced

Sodium hydroxide is industrially produced by electrolysis of brine. Other production methods are also described below.

1. Electrolysis of Brine
Brine electrolysis is the most common method of sodium hydroxide production using electrolysis and ion exchange membranes. In this method, brine (NaCl) is electrolyzed to produce sodium hydroxide (NaOH) and chlorine (Cl2).

2. Treatment of Salt With Calcium Hydroxide
Ca(OH)₂ + 2NaCl → 2NaOH + CaCl₂
In this method, sodium hydroxide is produced by the reaction of calcium hydroxide and sodium chloride.

3. Ammonia Treatment of Sodium Hydroxide
2NH₃ + 2NaCl + H₂O → 2NaOH + 2NH₄Cl
In this method, ammonia (NH₃) reacts with brine (NaC) to produce sodium hydroxide.

4. Complex Decomposition Reaction of Calcium Hydroxide (Slaked Lime) and Sodium Carbonate
Ca(OH)₂ + Na₂CO₃ → 2NaOH + CaCO₃
Sodium hydroxide can also be obtained by mixing a solution of calcium hydroxide and sodium carbonate.

Each production method may require subsequent refining for purity.

What Is Cobalt Hydroxide?

Cobalt hydroxide, known in forms as cobalt (II) hydroxide and cobalt (III) hydroxide, is primarily utilized in its cobalt (II) state. It is classified under various safety and health regulations, indicating the need for careful handling and use of protective equipment due to its potential health risks.

Uses of Cobalt Hydroxide

Cobalt hydroxide is integral in producing cobalt metal, cathode materials for nickel-hydrogen batteries, metallic soaps, paint desiccants, and as a catalyst. It improves electrode conductivity in batteries by transforming into cobalt oxyhydroxide upon initial charging.

Properties of Cobalt Hydroxide

1. Cobalt Hydroxide (II)

This light reddish powder is stable under normal conditions but can oxidize in air or with oxidants to cobalt hydroxide (III). It’s insoluble in water but dissolves in aqueous ammonia and ammonium salt solutions, posing irritation risks and requiring airtight storage.

2. Cobalt Hydroxide (III)

As a dark brown powder, cobalt (III) hydroxide is insoluble in water, ethanol, nitric acid, sulfuric acid, and aqueous ammonia.

Structure of Cobalt Hydroxide

1. Cobalt Hydroxide (II)

With the formula Co(OH)₂, this compound features a hexagonal cadmium hydroxide-type crystal structure, with a density of 3.597 g/cm³.

2. Cobalt Hydroxide (III)

Typically existing as Co₂O₃･nH₂O, it predominantly occurs in a hydrated form with variable water content.

Other Information on Cobalt Hydroxide

1. Cobalt Hydroxide (II) Production

Produced by reacting an aqueous cobalt salt solution with sodium hydroxide in the presence of glucose, it initially forms a blue precipitate that stabilizes to light red over time.

2. Reaction of Cobalt Hydroxide (II)

As an amphoteric compound, cobalt (II) hydroxide dissolves in acids and alkalis, with its solubility product being approximately 1.3 x 10^-15.

3. Reaction of Cobalt Hydroxide (III)

Cobalt (III) hydroxide forms when a cobalt (III) salt solution reacts with sodium hydroxide and dehydrates to a monohydrate at 100°C, eventually producing chlorine when dissolved in hydrochloric acid.

What Is Potassium Hydroxide?

Potassium hydroxide (KOH), also known as caustic potash, is a highly caustic compound that poses significant risks upon skin contact, necessitating the use of protective gear such as glasses and rubber gloves. This colorless orthorhombic crystal readily absorbs moisture from the air, transforming into potassium carbonate upon reacting with carbon dioxide. Its aqueous solutions are intensely alkaline and corrosive, especially when dissolved in water, where it releases heat.

Uses of Potassium Hydroxide

Potassium hydroxide is pivotal in various industrial applications:

1. Detergents

Utilized in creating liquid soaps, lotions, and shampoos, potassium hydroxide aids in producing potassium salts of fatty acids, which are highly soluble in water. It’s also employed in wineries for cleaning purposes.

2. Food Industry

As a food industry staple, it acts as a stabilizer, thickener, and pH adjuster, extending product shelf life. Additionally, potassium hydroxide-based fertilizers, derived from coal combustion ash and processed at high temperatures, enhance agricultural productivity.

Properties of Potassium Hydroxide

With a molecular weight of 56.11 and a specific gravity of 2.044, potassium hydroxide melts at 380°C and boils at 1324°C. It dissolves in water (121g per 100 mL at 25°C) and is soluble in ethanol and methanol. It reacts with acids, producing salts, and is corrosive to certain metals, generating flammable gases. It also reacts with ammonium salts to release ammonia.

Other Information on Potassium Hydroxide

1. Synthesis of Potassium Hydroxide

Potassium hydroxide is synthesized through:

• Electrolysis of Potassium Chloride Solution: A method generating hydrogen and chlorine gases to produce potassium hydroxide.
• Reaction with Aqueous Potassium Carbonate and Slaked Lime: This substitution reaction between potassium carbonate and calcium ions in slaked lime yields potassium hydroxide.
• Reaction of Potassium Metal with Water: Although this exothermic reaction produces potassium hydroxide, it poses significant risks of fire or explosion.

2. Health Effects of Potassium Hydroxide

While used as a food additive, potassium hydroxide’s caustic nature can cause ulcers, digestive irritation, and skin or eye injuries. Proper safety measures are crucial to mitigate health risks.