月: 2023年1月

What Is Salicylic Acid?

Salicylic acid is a compound used in topical applications for skin disorders and as an analgesic oral medication. However, if taken as is, salicylic acid may cause peritonitis due to gastrointestinal side effects. It is a beta-hydroxy acid and one of the plant hormones.

Salicylic acid is relatively easy to chemically synthesize. It is also widely found in nature, specifically in the species Cyperus rotundus and Cyperus rotundus. It is also present in the form of methyl salicylate, an ester of salicylic acid, in plant essential oils such as wintergreen oil and birch oil.

Uses of Salicylic Acid

Salicylic acid has bactericidal, anti-inflammatory, analgesic, and skin-softening properties. For this reason, it is often used in the pharmaceutical field, mainly as a topical agent for skin diseases. In addition, acetylsalicylic acid, a derivative of salicylic acid, can be widely used as an analgesic oral drug because its side effects when taken internally are reduced while maintaining the analgesic effect of salicylic acid.

Furthermore, it is also used in facial cleansers for exfoliation, as a dye intermediate, and as an antiseptic. In the past, it was also used as a preservative in foods but is currently not available as a food additive.

Properties of Salicylic Acid

Salicylic acid is a solid at room temperature and pressure, a colorless needle-like crystal with sublimation properties. Its melting point is 159°C, boiling point at 2.6 kPa is about 211°C, and its flash point and flash point are 157°C and 545°C, respectively.

It is soluble in ethanol and ether and insoluble in water. It is odorless and has a slightly sour taste.

Structure of Salicylic Acid

Salicylic acid has the structure of a benzene with one hydrogen atom replaced by a carboxy group and one hydrogen atom in the ortho position of the carboxy group replaced by a hydroxyl group.

The chemical formula is C₇H₆O₃ with a molar mass of 138.12 g/mol. The specific formula is HOC₆H₄COOH, and the density is 1.443 g/cm³.

Other Information on Salicylic Acid

1. Synthesis of Salicylic Acid

Salicylic acid has a relatively simple chemical structure, so there is no need to extract it from willow, and its total synthesis is straightforward. Industrially, salicylic acid is liberated by reacting sodium phenoxide with carbon dioxide under high temperature and pressure, followed by the addition of sulfuric acid or hydrochloric acid.

The process of producing salicylic acid using this series of reactions is called the Kolbe-Schmitt reaction. In contrast, the reaction of potassium phenoxide with carbon dioxide under the same conditions can introduce a carboxy group at the para position.

Para-hydroxybenzoic acid is formed in approximately 90% of the reactions. Methyl esters to butyl esters are called parabens and are used as preservatives.

2. Reaction of Salicylic Acid

Salicylic acid, which has a phenolic hydroxyl group, reacts with ferric chloride in an aqueous solution to produce a blue to reddish-purple color. Reaction with acetic anhydride results in acetylation to form acetylsalicylic acid. Acetylsalicylic acid is one of the typical antipyretic analgesics. It is a drug synonymous with non-steroidal anti-inflammatory drugs and has anti-inflammatory, antipyretic, analgesic, and antiplatelet effects.

3. Action of Salicylic Acid

One of the actions of salicylic acid is the activation of AMP-activated protein kinase (5′ adenosine monophosphate-activated protein kinase). This is said to explain some of the effects of salicylic acid and Aspirin.

4. Metabolism of Salicylic Acid

Salicylic acid administered to humans may be excreted directly from the kidneys into the urine without being metabolized. For example, even when salicylic acid is high in human blood, such as during poisoning when a large dose of acetylsalicylic acid is taken, a large amount of salicylic acid can still be excreted in the urine.

The excretion of salicylic acid in urine increases especially when the pH of the urine is tilted toward the alkaline side. When more than 50 μg/ml of salicylic acid is present in the urine, a color reaction occurs with ferric chloride solution.

What Is Choline?

Choline (C5H14NO) is a water-soluble, vitamin-like substance synthesized in the body from amino acids such as serine and methionine. It appears as a colorless, alkaline liquid and is a crucial component in various biological processes.

Choline is a part of phosphatidylcholine (lecithin), found in cell membranes, and acetylcholine, a neurotransmitter. It plays a significant role in reducing cholesterol deposition in blood vessel walls and preventing fat accumulation in the liver. As a component of acetylcholine, it helps in dilating blood vessels and lowering blood pressure, contributing to the prevention of hypertension, arteriosclerosis, and fatty liver.

Uses of Choline

Choline is widely used as a dietary supplement to improve memory, concentration, and overall brain function. Its benefits extend to preventing conditions like high blood pressure, arteriosclerosis, and fatty liver.

In the agricultural sector, choline is added to livestock feed to prevent fat accumulation in the liver, ensuring the health of the animals. It also finds use in plant growth promotion, with choline-based pesticides being utilized in farming.

What Is Germanium?

Germanium is a grayish-white, hard, brittle solid.

Germanium’s element symbol is Ge, its atomic number is 32, and its CAS number is 7440-56-4. It is classified as a “semimetallic element,” a substance intermediate between metals and nonmetals. It is a substance extracted from ores and soil in nature and was discovered by the German scientist Winkler in 1885. It is classified as a rare metal because only about 0.00014% of it exists on the earth and its mining is limited.

Germanium compounds can be broadly classified into two types: organic and inorganic germanium compounds.

Uses of Germanium

1. Inorganic Germanium

Inorganic germanium, such as germanium oxide, is used as an industrial raw material for diodes, transistors, infrared lenses for night vision cameras, optical fibers, catalysts in the manufacture of PET bottles, health accessories such as bracelets, and germanium hot baths. Germanium oxide, with its high refractive index and low optical dispersion, is particularly useful as a dopant in the core of wide-angle cameras, microscopes, and optical fibers. Germanium can be alloyed with silicon, and circuits that take advantage of the heterojunction properties of germanium and silicon are fast, making silicon-germanium alloys an important semiconductor material for high-speed integrated circuits. In addition, semiconductor detectors made of single-crystal high-purity germanium are utilized in airport security to detect radiation sources.

2. Organic Germanium

While inorganic germanium is insoluble in water and accumulates in the body, causing harm, organic germanium is mainly used in health foods and cosmetics because it is water soluble and is also found in plants known to be good for the body, such as ginseng and aloe.

Properties of Germanium

Germanium has a melting point of 937°C and a boiling point of 2,850°C. It exists as a solid at room temperature, and its density in the solid state is 5.35 g/cm³. It is insoluble in dilute acids and alkalis, but slowly dissolves in hot concentrated sulfuric and nitric acids, and reacts violently with molten alkalis to form germanates ([GeO₄]^4-). It has a narrower band gap (0.7eV) than silicon, making it a useful semiconductor element.

Structure of Germanium

Germanium has three different crystal structures, depending on temperature and pressure. At room temperature and pressure, it has a cubic structure similar to diamond, called α-germanium, and at higher pressures, it has a tetragonal structure similar to β-Tin, called β-germanium. There is also a structure called germanene, which is created by a process similar to graphene, using a high vacuum and high temperature to deposit layers of germanium atoms on a substrate, and is considered a material that exhibits more abundant physical properties than graphene.

Other Information on Germanium

1. How Germanium Is Produced

Germanium is produced primarily from sphalerite but is also found in silver, lead, and copper ores. Germanium in ores is mostly sulfides, which are converted to oxides by heating them under air (GeS₂+3O₂→GeO₂+2SO₂). High-purity germanium oxide can be reduced with hydrogen (GeO₂+2H₂→Ge+2H₂O) to yield products suitable for infrared optics and semiconductor manufacturing, while reduction with coke (GeO₂+C→Ge+CO₂) yields products for steel production and industrial products.

2. Legal Information

Germanium is not subject to any of the major laws and regulations, such as the Poisonous and Deleterious Substances Control Law, the Fire Service Law, and the Pollutant Release and Transfer Register Law (PRTR Law).

3. Handling and Storage Precautions

Handling and storage precautions are as follows

• Seal the container tightly and store it in a dry, cool, and dark place.
• Use only outdoors or in well-ventilated areas.
• Avoid contact with strong oxidizing agents.
• 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 Glycine?

Glycine is an amino acid with only hydrogen atoms in its side chain.

It is one of the 20 amino acids that make up proteins and is the only one of them that does not have a chiral carbon atom. It is abbreviated as Gly or G.

Glycine has a variety of functions and can be produced in the human body. It is particularly essential in the central nervous system and is present in high concentrations in the spinal cord and brain stem. It is a major amino acid in collagen and accounts for about one-third of the collagen in the body.

Uses of Glycine

Glycine has a chelating effect, making metals more soluble. This property can be used as a cleaning and polishing agent for precision instruments. It is an environmentally friendly chelating agent because it is easily decomposed by microorganisms. Glycine can be used in a variety of foods as a seasoning or as a means of improving shelf life.

Besides that, being the simplest amino acid, it is also used as a synthetic raw material for other amino acids. In addition to that, it can be used as a raw material for a wide variety of biological substances, such as collagen, porphyrins, glutathione, and creatine.

Properties of Glycine

Glycine is a white solid. It is soluble in ethanol and pyridine, but not in ether. It is soluble in water. The acid dissociation constant of the carboxyl group is pK_a = 2.34 and that of the amino group is pK_a = 9.6. It has a natural sweetness and excellent bacteriostatic properties that inhibit the action of bacteria.

Structure of Glycine

Glycine is 2-aminoacetic acid. It is also one of the 20 amino acids specified in the DNA of earth organisms. The side chain of the amino acid structure is a hydrogen atom (-H) and has no chiral carbon. Therefore, it is the only α-amino acid that has no stereoisomers (D-, L-) among the α-amino acids that make up living organisms.

The chemical formula is C₂H₅NO₂ with a molar mass of 75.07 g/mol. Its specific formula is H₂NCH₂COOH and its density is 1.1607 g/cm³. Glycine is classified as a nonpolar side-chain amino acid. It is an amphoteric ion and dissociates on both the acidic and alkaline side. Specifically, it becomes an ammonium cation at pH = less than 2.4 and a glycinate at pH = greater than 9.6.

Other Information on Glycine

1. Biosynthesis and Metabolism of Glycine

The glycine cleavage system cleaves glycine by tetrahydrofolate to 5,10-methylenetetrahydrofolate. On the other hand, glycine can be reversibly interconverted to L-serine by the action of glycine hydroxymethyltransferase. The reaction is then catalyzed to convert 5,10-methylenetetrahydrofolate to tetrahydrofolate.

If glycine is deaminated, glycolic acid is formed, and oxidation yields glyoxylate. In humans, glyoxylate is an intermediate in the metabolism of ethylene glycol to oxalic acid. Oxidation produces oxalic acid, which is toxic. Metabolism of glycine is important to avoid oxidative reactions.

2. Reaction of Glycine

With acid chloride, glycine is converted to amide carboxylic acids such as horse uric acid and acetylglycine. With nitrite, glycine yields glycolic acid. In the reaction of glycine with methyl iodide, the amine is quaternized and the natural product trimethylglycine can be produced.

Besides, glycine can be condensed to form peptides. The first step is the formation of glycylglycine, a dipeptide of glycine. Other steps include the thermal decomposition of glycine and glycylglycine to yield 2,5-diketopiperazine, a cyclic diamide.

Glycine also forms esters with alcohols and can be isolated as glycine methyl ester hydrochloride. Furthermore, because of its amino and carboxy groups, it reacts with a variety of reagents as a bifunctional molecule.

What Is Chloroform?

Chloroform, also known as trichloromethane, is an aliphatic chlorine compound. It is a colorless liquid with a pungent odor, insoluble in water but soluble in diethyl ether, acetone, and benzene. Due to its reactivity, it is stored at low temperatures with stabilizers to prevent peroxide formation and violent polymerization.

Uses of Chloroform

Chloroform’s main applications include:

• Production of chlorodifluoromethane and chlorofluorocarbons, which are used in fluoropolymers like polytetrafluoroethylene (PTFE) and fluorinated refrigerants.
• Extraction solvent in pharmaceuticals and agrochemicals for substances like antibiotics, vitamins, and alkaloids.
• Deuterated chloroform as a solvent in NMR measurements.
• Historically, as an inhalant anesthetic, though its use has been discontinued due to health risks.

Characteristics of Chloroform

Chloroform is highly volatile, with a boiling point of 61°C and a melting point of -64°C. It is nonflammable in liquid form but combustible as a vapor. In the presence of air, it decomposes to form phosgene, dichloromethane, and other compounds. It is stabilized with additives like methanol or ethanol.

Other Information on Chloroform

1. Synthesis of Chloroform

Chloroform is produced industrially by heating chlorine with chloromethane or methane at about 500°C, followed by distillation. It can also be synthesized from ethanol or acetone with calcium hypochlorite, or by reducing carbon tetrachloride with hydrogen. Natural sources include seaweeds, fungi, and chlorinated tap water.

2. Safety of Chloroform

Inhalation of chloroform can lead to respiratory, liver, and kidney toxicity. Symptoms include coughing, dizziness, nausea, and in severe cases, a slow heartbeat or death. It can irritate the eyes and skin. Proper protective equipment, such as safety glasses and gloves, should be used when handling chloroform.

What Is Chlorobenzene?

Chlorobenzene is an aromatic halide in which one hydrogen in the benzene ring is replaced by chlorine.

Formerly called chlorobenzol, the name is still used in some cases. Chlorobenzene usually refers to the monosubstituted form, monochlorobenzene.

Chlorobenzene is a colorless liquid that is used in a wide variety of applications as a raw material intermediate for many organic compounds. It is mainly available as a raw material for diphenyl ether and chloronitrobenzene. It is a hazardous material classified as Class 4 Petroleum No. 2 under the Fire Service Act.

Uses of Chlorobenzene

Chlorobenzene is used as a raw material for organic compounds, pharmaceutical intermediates, and dye intermediates. Its reactivity in electrophilic substitution reactions is higher than that of benzene, making it useful as a raw material for many compounds.

Chlorobenzene was once used in large quantities as a raw material for DTT (dichlorodiphenyl trichloroethane), an organochlorine insecticide. In Japan, chlorobenzene was also actively used as a quarantine agent against lice and other insects, but DTT is now banned as an environmental pollutant.

Properties of Chlorobenzene

Chlorobenzene has a melting point of -45.2°C, a boiling point of 131°C, and a flash point of -19°C.

The half-lethal dose (LD₅₀) is 2.9 g/kg, indicating low to moderate toxicity. The permissible exposure limit is 75 ppm (350 mg/m³) as an 8-hour weighted average for workers handling chlorobenzene.

Structure of Chlorobenzene

Chlorobenzene is an aryl halide. It has a molecular weight of 112.56, a chemical formula of C₆H₅Cl, a density of 1.1066 at 20°C, and a refractive index (n_D) of 1.525.

Other Information on Chlorobenzene

1. Synthesis of Chlorobenzene

Chlorobenzene was first synthesized in 1851 by the reaction of phosphorus pentachloride and phenol; in 2014, chlorobenzene was reported to be present in Martian rocks.

It is now synthesized industrially by the substitution reaction of benzene with chlorine, using iron or iron chloride as a catalyst. As the chlorine substitution proceeds, dichlorobenzene may be produced, but it can be easily separated by cooling and recrystallization.

In the laboratory, it can be synthesized from aniline via benzenediazonium chloride using the Sandmeyer reaction. The Zandmeier reaction is a chemical reaction that uses copper salts as catalysts to obtain aryl halides from aromatic diazonium ions.

2. Reaction of Chlorobenzene

Nitration of chlorobenzene yields a mixture of 2-nitrochlorobenzene and 4-nitrochlorobenzene. These mononitrochlorobenzenes can be separated and used in nucleophilic substitution reactions for chloride, respectively. For example, from 2-nitro chlorobenzene, sodium hydroxide, sodium methoxide, sodium disulfide, and ammonia convert to 2-nitrophenol, 2-nitroanisole, bis(2-nitrophenyl)disulfide, and 2-nitroaniline. 4-nitrochlorobenzene is also similarly available.

One method of synthesizing phenol is to heat chlorobenzene, obtained by chlorinating benzene, with an aqueous solution of sodium hydroxide at high temperatures. In this reaction, sodium chloride is produced as a byproduct. However, the cumene process is often used for the industrial production of phenol.

What Is Chlorosulfonic Acid?

Chlorosulfonic acid is an inorganic compound with the chemical formula HSO₃Cl or SO₂Cl(OH).

It is also called “sulfuric chloride” or “hydrogen chlorotrioxosulfate. The formula weight is 116.52 g/mol, melting point is -80 °C, density is 1.753 g/cm³, and CAS number is 7790-94-5. At room temperature and pressure, it is a colorless to pale yellow cloudy oily liquid with a strong pungent odor.

Uses of Chlorosulfonic Acid

Chlorosulfonic acid is used as a sulfonating agent in raw materials for synthetic detergents, pharmaceuticals, and dyes. Chlorosulfonic acid has a variety of uses and is consumed in large quantities in Japan.

1. Reactant in Organic Chemistry

Chlorosulfonic acid is mainly used as a reactant in sulfonation reactions. Sulfonation is a reaction in which a hydrogen atom of an organic compound is replaced by a sulfur group. Usually, sulfuric acid, fuming sulfuric acid, or acetyl sulfuric acid is used. Chlorosulfonic acid is particularly useful as a sulfonation reagent for compounds that are difficult to react with.

The reason for this is that the chlorine atom bonded to the sulfur atom is removed as a chloride ion in the sulfonation reaction, and this substitution reaction proceeds quickly because the chloride ion is very stable and excellent as a leaving group.

Another reason is that the use of chlorosulfonic acid is less expensive, and the intense sulfonation reaction using sulfuric acid produces a variety of unnecessary byproducts, which can be suppressed. However, there is a disadvantage in that the reactivity is very high and must be controlled.

The introduction of sulfo groups is very important because many neutral detergents have sulfo groups and quaternary amines at both ends, making them charge-neutral. Many dyes also have sulfo groups in their molecules. Therefore, this sulfonation reaction is an important process in the manufacture of neutral detergents and dyes, and chlorosulfonic acid is a raw material in the manufacture of neutral detergents and dyes.

2. Other

Since chlorosulphonic acid reacts with water to form white smoke of hydrochloric acid and sulfuric acid, it is also used as a raw material for smoke screens used in military settings and is sprayed into the exhaust of stealth bombers to adsorb moisture in the exhaust to suppress the generation of airplane clouds from the exhaust of the bomber’s engine.

Properties of Chlorosulfonic Acid

Chlorosulfonic acid is a highly reactive substance and reacts violently with water and ethanol. When reacting with water in particular, it decomposes to produce sulfuric acid and hydrochloric acid and is highly hygroscopic and fumes in the air.

Therefore, it is important to select a solvent with no nucleophilic properties when dissolving it in a solvent. It is soluble in chloroform, dichloromethane, and pyridine, but insoluble in carbon disulfide and carbon tetrachloride.

Other Information on Chlorosulfonic Acid

1. Synthesis of Chlorosulfonic Acid

Chlorosulfonic acid can be synthesized by reacting phosphorus pentachloride with concentrated sulfuric acid. It can also be synthesized by reacting sulfur trioxide with hydrochloric acid.

2. Hazards of Chlorosulfonic Acid

Chlorosulfonic acid is classified as a deleterious substance under the Poisonous and Deleterious Substances Control Law. It is highly corrosive and causes severe chemical wounds when it comes into contact with the skin, so it should be handled with care. It is highly irritating not only to the skin but also to the eyes, and if ingested can cause severe damage to internal organs.

If it comes into contact with the skin, it is important to immediately wash it off with large amounts of water. If swallowed, immediate medical attention should be sought.

If left in the air, hydrogen chloride and sulfuric acid will react with moisture in the air to form dangerous hydrogen chloride and sulfuric acid, respectively. When handling, it is essential to wear a lab coat, protective clothing, rubber gloves, and safety glasses.

What Is Chromic Acid?

Chromic acid is a compound represented by H₂CrO₄.

Chromic acid is also used to refer collectively to substances in which Chromium Oxide (Ⅵ) dissolves in water to form Chromic acid salts. It has a molecular weight of 118.0 g/mol, a melting point of 197°C, a density of 1.201 g/cm³, and a CAS number of 7738-94-5. The molecule is equal to one molecule of water added to Chromium trioxide.

Uses of Chromic Acid

1. Oxidizing Agent

Chromic acid, other chromates, and compounds containing hexavalent chromium such as chromium trioxide are powerful oxidants and are often used in organic synthesis. They are often used primarily to obtain carboxylic acids by acting on primary alcohols or to obtain ketones by acting on secondary alcohols. It is named Jones oxidation, Sallet oxidation, or Collins oxidation, depending on the reagent and solvent conditions. Since chromic acid is a very strong oxidizing agent, side reactions may occur, such as further oxidation of the target compound to yield an unexpected compound and great care must be taken. PCC, a salt formed from chlorochromic acid ion and pyridinium ion, in which the hydrogen atom of the chromic acid ion is replaced by a chlorine atom, is a mild oxidant and can oxidize primary alcohols to aldehydes. In these oxidation reactions, chromic acid is reduced to trivalent Chromium.

2. Surface Treatment Agents

It is used as a photographic, plating, pigment, leather tanning, dye, and dyeing agent. It is also useful for chromic acid treatment, one of the metal passivation methods. By immersion or cathodic electrolysis in the treatment solution, a corrosion-resistant coating can be imparted. This chromic acid treatment is effective in improving corrosion resistance, paint adhesion, and preventing discoloration. Care must be taken when using chromic acid and Dichromic Acid (hexavalent chromium), as they are highly oxidizing and strongly corrode skin and mucous membranes, causing dermatitis and chrome ulcers.

Properties of Chromic Acid

Chromic acid is a red solid at normal temperature and pressure, with a decomposition point of 250°C. A normal concentration of chromic acid solution is yellowish red, but at higher concentrations, it turns red or dark red and becomes blackish.

In an aqueous solution, two molecules of chromic acid and two molecules of Oxonium Ion combine to form one molecule of Dichromic Acid and three molecules of water molecules. In strongly acidic or basic conditions below pH 1, the equilibrium is tilted in the direction of chromic acid formation.

Other Information on Chromic Acid

1. Hazards of Hexavalent Chromium

Hexavalent Chromium, including chromic acid, is notorious for being extremely toxic. There are two types of Chromium ions: trivalent and hexavalent. While trivalent Chromium is widely found in nature in a stable form, hexavalent Chromium is found only in some ores. Hexavalent Chromium can cause dermatitis when it adheres to human skin and can cause vomiting if ingested into the body. Furthermore, it is carcinogenic because of its ability to damage DNA and can cause lung cancer if inhaled, while long-term ingestion has the potential to cause suspension bridges and stomach cancer. Therefore, when handling hexavalent chromium in powder form, it is necessary to prevent it from scattering into the surroundings and to strictly control it so that it does not get into the eyes, nose, or mouth, and also so that it does not remain on the skin or clothing.

2. Various Chromic Acid Salts

Chromium ions with an oxidation number of 6 are called hexavalent chromium, and the ions are present in aqueous solution in the form of CrO₄2-, HCrO₄-, Cr₂O₇2-, etc. These ions also polymerize to produce the polyacid ions Cr₃O₁₀2- and Cr₄O₁₃2-. These ions are usually used in the form of sodium or potassium salts (such as K₂Cr₂O₇ and Na₂Cr₂O₇) and are usually characterized by a yellow or red color.

What Is Chromium?

Chromium is a metallic element with atomic number 24 and element symbol Cr.

It was named by René Just Haüy after the Greek word chroma, meaning color, because compounds of chromium have a variety of colors.

Chromium is mainly extracted from chromite ore (FeCr2O4). More than 90% of the world’s chromium resources are concentrated in two countries, South Africa and Kazakhstan, and are highly unevenly distributed.

Uses of Chromium

Chromium is used primarily in the steel industry. Alloys of chromium and iron containing more than 12% chromium are called stainless steels and are widely used in machinery and kitchenware as a rust-resistant metal with high corrosion resistance. In addition, chromium metal is available as a plating because of its luster and high corrosion resistance.

Chromium is also an essential mineral involved in human metabolism. In particular, its ability to stimulate lipid metabolism helps lower cholesterol levels and neutral fats and can prevent arteriosclerosis and hypertension. It also helps insulin work and is said to be effective in preventing diabetes.

Properties of Chromium

Chromium is a hard, silvery-white metal with a melting point of 1,907°C and a boiling point of 2,671°C. It is extremely stable at room temperature.

When dissolved in hydrochloric acid or dilute sulfuric acid, it forms a solution of divalent chromium salts, which are quickly oxidized to trivalent chromium by oxygen in the air due to its unstable divalent state.

Structure of Chromium

The electron configuration of chromium is [Ar] 3d⁵ 4s¹. The crystal structure is a body-centered cubic lattice for α, a cubic close-packed structure for β, and a hexagonal close-packed structure for γ.

Other Information on Chromium

1. Chromium in the Body

Chromium is a trace essential element for humans. It is a material used to make up glucose tolerance factors that help bind insulin and receptors in the body. When the body is deficient in chromium, abnormalities in glucose metabolism may occur and diabetes may develop.

Examples of foods rich in chromium include shrimp, liver, mushrooms, beans, brewer’s yeast, and black pepper. The daily requirement for chromium is 50 to 200 µg.

Unrefined grains contain it, but most chromium is lost during refining. It is reported that 98% of chromium is lost when flour is refined and 92% of chromium is lost when rice is refined. Furthermore, chromium is a mineral that is difficult to absorb into the body. Supplements are available to help the body absorb chromium.

2. Dangers of Chromium

Chromium alone and trivalent chromium are not toxic. However, hexavalent chromium compounds are highly toxic. In the past, hexavalent chromium was used for plating, but it is no longer used in chromate treatment of zinc plating due to soil contamination and other problems.

Chromium is a carcinogen found in cigarettes; tetravalent chromium compounds have been reported to be carcinogenic.

3. Isotopic Applications of Chromium

53Cr is a decay product of 53Mn, and isotopic contents of chromium and manganese are related and available in isotopic geology. Given the compositional ratios of chromium and manganese isotopes, the presence of 26Al and 107Pd in the early solar system is an indication that these isotopes were present in the early solar system. The diverse compositional ratios of 52Cr and 53Cr and Mn and Cr in the asteroid suggest that 53Mn decayed early in the formation of the object.

What Is Krypton Gas?

Krypton gas is an element with atomic number 36.

It belongs to group 18 of the periodic table and is classified as a noble or inert gas because of its minimal chemical reactivity. Krypton gas has a boiling point higher than that of oxygen, which makes it a byproduct in the production of air separation gases such as oxygen, nitrogen, and argon. Highly pure krypton gas can be obtained when liquid oxygen containing krypton gas is separated from its components in a purifier.

Uses of Krypton Gas

Krypton gas is widely used as an inert and nonflammable gas because it does not react easily with other substances. A notable application is as an encapsulating gas in lighting and lamps. Krypton gas has low thermal conductivity, which can reduce heat loss through heat dissipation from the filament of a light bulb. It is said to improve lamp efficiency by about 10% compared to argon-filled bulbs. Furthermore, krypton gas, with its high heat insulation properties, is also used as a building material. Windows sealed with krypton gas can increase the heating efficiency of entire indoor spaces.

In advanced fields, krypton fluoride (KrF) is widely used as a light source for etching lasers in semiconductor manufacturing.

Properties of Krypton Gas

Krypton gas has a melting point of -157.2 °C (-251 °F) and a boiling point of -152.9 °C (-243.2 °F). It is a colorless, odorless gas at room temperature and pressure. It is present in air at about 1.14 ppm. It is obtained by the liquefaction of air and fractional distillation.

Krypton gas has a specific gravity of 2.82 at -157 °C (-251 °F). It is a heavy gas and can lower the pitch of a person’s voice when inhaled. It has no valence electrons in its outermost shell, making it chemically stable.

Structure of Krypton Gas

There are 31 known isotopes of krypton gas. In nature, there are five stable isotopes and one radioactive isotope. It can form inclusion compounds with water and hydroquinone. The chemical formulas are Kr – 6H₂O and Kr – 3C₆H₄(OH)₂. Crystals of krypton gas (Kr(H₂)₄) are obtained above 5 GPa. These crystals have a face-centered cubic structure with the octahedron of krypton gas surrounded by randomly oriented hydrogen molecules.

Other Information on Krypton Gas

1. Isotopes of Krypton Gas

⁸¹Kr is produced by reactions in the atmosphere. It has a half-life of 250,000 years and is the natural isotopic source of krypton gas. Krypton gas near the water surface is very volatile, and ⁸¹Kr is used to date groundwater from 50,000 to 800,000 years.

⁷⁸Kr is a nuclide in which double electron capture occurs. However, its probability is low and its half-life is estimated to be over 1.1 x 10²⁰ years. ⁸⁵Kr, an inert radioactive gas, has a half-life of 10.76 years. It is produced by the fission reaction of plutonium or uranium, is manufactured in nuclear reactors, and is released entirely into the environment during the fuel rod reprocessing process.

In the 1940s, the atmospheric concentration of ⁸⁵Kr was less than 0.001 becquerels per m³ of air. However, the current concentration is more than 1 becquerel in 1 m³ of air. Concentrations are reported to be 30% higher in the Arctic than in the Antarctic. This is because most of the reactors are located in the northern hemisphere. ⁸⁵Kr becomes ⁸⁵Rb by beta decay.

2. Compounds of Krypton Gas

Krypton gas is inert, but it can form unstable compounds with fluorine and an oxidation number of +2. Krypton difluoride (KrF₂) is a volatile solid and is represented by the chemical formula KrF₂. The molecular structure of KrF₂ is linear and the Kr-F distance is 188.9 pm. Reaction with strong acids produces cations such as KrF⁺ and Kr₂F₃⁺.

The reaction of KrF₂ with B(OTeF₅)₃ can produce Kr(OTeF₅)₂, an unstable compound containing a krypton-oxygen bond. Krypton-nitrogen bonds are also found in [HC=N–Kr–F]⁺ produced by the reaction of KrF₂ with [HC=NH]⁺[AsF₆^–] below -50°C. HKrCN and HKrC=CH are reported to be stable up to 40K.