月: 2023年7月

Inclinómetros Digitales

¿Qué es un Inclinómetro Digital?

Los inclinómetros digitales son herramientas de medición que permiten determinar la inclinación o el ángulo de un objeto. La información capturada se presenta en una pantalla LCD digital. A diferencia de los inclinómetros analógicos, estos dispositivos tienen la capacidad de establecer una posición de referencia arbitraria y calcular el ángulo en relación a dicha referencia. Esto garantiza una alta precisión de medición y un rango amplio de aplicaciones tanto en investigaciones como en la industria.

Por ello, se utilizan para tareas como trabajos de fontanería y drenaje, construcción de edificios con estructura de acero, instalación de equipos y dispositivos médicos. Existen dos tipos principales de métodos de medición de ángulos: uno utiliza la tecnología MEMS y el otro utiliza la inclinación del electrolito.

Aplicaciones de los Inclinómetros Digitales

1. Obras de Corte y Construcción

Los inclinómetros digitales se utilizan para medir el ángulo de incidencia de las brocas en las obras de corte. Si el ángulo se desvía del ángulo objetivo, cambia la dirección del corte, lo que supone una pérdida de trabajo y un peligro.

También son útiles para medir el ángulo de las grúas en las obras. La medición del ángulo permite predecir peligros. Se pueden realizar fácilmente mediciones horizontales y verticales de estructuras de acero y tuberías.

2. Paneles Solares

Se utiliza para el seguimiento solar de paneles fotovoltaicos. Se monta directamente sobre el objeto de medición con el fin de obtener una carga suficiente.

3. Otros

Otra aplicación es el ajuste horizontal y vertical durante la instalación de maquinaria de precisión, instrumentos de medición, cuadros de distribución, etc. Se utilizan para medir el ángulo del brazo de robots y otros equipos automáticos.

Además, los inclinómetros digitales también se utilizan en la industria médica, donde se emplean para determinar con precisión el ángulo del rotador de medición en equipos de TAC y rayos X. El posicionamiento de la cama en la que yace el paciente permite localizar con precisión lesiones en el cuerpo humano.

Principios de los Inclinómetros Digitales

1. Método MEMS

Los sensores de inclinación emplean la tecnología MEMS (Sistemas Micro Electro Mecánicos), en la que se establece una matriz de electrodos dentro de una cámara completamente sellada. Uno de los electrodos permanece fijo, mientras que el otro puede moverse libremente al estar conectado a un resorte elástico. El otro polo se desplaza libremente mediante una conexión de muelle a resorte.

Cuando se inclina el sensor de inclinación, la posición del electrodo del extremo libre cambia en relación con el electrodo del extremo fijo, y al mismo tiempo se genera una diferencia de capacitancia antes y después del cambio. La diferencia de capacitancia en ese momento se convierte en un ángulo.

2. Método Electrolítico

En los sensores de inclinación que utilizan la tecnología electrolítica, se montan dos pares de electrodos en el fondo de la cámara paralelos al eje de medición y se llenan de electrolito. Cuando se aplica una tensión entre los dos electrodos, la corriente forma un campo de dispersión. Como resultado, la cámara se inclina y el nivel del líquido cambia, al igual que el campo de dispersión.

La conductividad del electrolito es constante y el cambio de resistencia depende de su relación con el nivel del líquido. Como no hay más piezas móviles que el electrolito, el desgaste es mínimo y el electrolito es muy resistente a los golpes. El electrodo utilizado para la medición se sumerge en el electrolito y éste no se corroe.

Características de los Inclinómetros Digitales

1. Corte en V e Imán Incorporado

Las superficies de medición de la mayoría de los inclinómetros digitales son de corte en V para una excelente estabilidad incluso en tuberías. La superficie inferior, por ejemplo, tiene un imán incorporado, lo que hace que los trabajos en tuberías de acero, marcos de acero y plantas sean más eficientes.

2. Alta Precisión

La alta resolución y precisión pueden visualizarse digitalmente en dos ejes simultáneamente. Son posibles soluciones integrales para la nivelación precisa, la alineación, el perfilado de superficies y la medición de vibraciones. La precisión suele rondar los ±0,03-0,2º y la resolución, los 0,01-0,1º. Y elimina el ensayo y error de leer un eje cada vez, ahorrando tiempo y permitiendo un trabajo profesional de alta calidad.

3. Visualización Comparativa

Cualquier ángulo puede utilizarse como referencia 0° y visualizarse en comparación con otros ángulos. Por ejemplo, si una posición de 30° se establece como referencia 0° en el modo de comparación, una posición de 50° en el modo normal se mostrará como 20°.

4. Rendimiento a Prueba de Polvo y Agua

El sistema puede utilizarse de forma segura con las manos mojadas y en zonas polvorientas de la obra. La mayoría de las prestaciones a prueba de polvo y agua son equivalentes a la norma IP54 establecida por la CEI (Comisión Electrotécnica Internacional).

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Aisladores Digitales

¿Qué son los Aisladores Digitales?

Los aisladores digitales son componentes diseñados para establecer un aislamiento efectivo entre la transmisión y la recepción de señales digitales.

La función de “aislamiento” juega un papel crítico en los circuitos eléctricos al prevenir cortocircuitos y daños en los equipos. La correcta separación de componentes es fundamental para evitar que la corriente se desvíe hacia lugares no deseados, contribuyendo así a la supresión de ruidos y la transmisión de señales sin interferencias.

Además, los aisladores digitales son dispositivos electrónicos con una larga vida útil y un bajo consumo de energía, lo que los hace adecuados para su uso en una amplia gama de equipos.

Usos de los Aisladores Digitales

Los aisladores digitales tienen una amplia aplicación en circuitos electrónicos y equipos donde el aislamiento es esencial. Un ejemplo destacado es su uso en maquinaria industrial, donde se presentan significativas disparidades de voltaje dentro del equipo. Las secciones de alimentación eléctrica que requieren grandes tensiones o los motores de gran tamaño muy próximos a secciones que funcionan con tensiones bajas deben aislarse cuando existen grandes diferencias de tensión.

De este modo se evitan los daños causados por las altas tensiones aplicadas a piezas que funcionan a bajas tensiones. En segundo lugar, también se utilizan en equipos médicos como rayos X y DEA. Estos dispositivos médicos se utilizan a menudo con las manos, para evitar que la corriente eléctrica fluya hacia el exterior y provoque una descarga eléctrica.

En vehículos, como los eléctricos y los híbridos, se utilizan para proteger las ECU y otros equipos de a bordo en vehículos que utilizan fuentes de alimentación de alta tensión.

Principios de los Aisladores Digitales

Existen dos tipos de aisladores digitales: el “método de aislamiento magnético” y el “método de aislamiento capacitivo”.

1. Método de Aislamiento Magnético

Los aisladores digitales con aislamiento magnético utilizan bobinas en los lados de transmisión y recepción respectivamente. Mediante el uso de bobinas en transmisión y recepción, se realiza la conversión entre señales eléctricas y energía magnética.

Puede manejar altas velocidades, pero la desventaja es que cuanto mayor es la velocidad, mayor es el consumo de corriente. Además, las características de ruido son inferiores a las de los siguientes sistemas con aislamiento capacitivo.

2. Tipo de Aislamiento Capacitivo

Se trata de aisladores digitales que utilizan condensadores. En la transmisión y recepción, la señal eléctrica se convierte en una forma de carga y descarga utilizando un condensador. Los métodos de aislamiento capacitivo tienen unas características de ruido especialmente buenas y, al igual que los métodos de aislamiento magnético, pueden utilizarse a altas velocidades. Además, el consumo de corriente es independiente de la velocidad y es bastante desventajoso a bajas velocidades.

Ambos métodos tienen la ventaja de una larga vida útil y altas velocidades, y ofrecen un rendimiento superior al de los aisladores anteriores. Sin embargo, la única desventaja es que los aisladores digitales sólo pueden manejar señales digitales y no señales analógicas.

Estructura de los Aisladores Digitales

La estructura de un aislador digital con aislamiento magnético consiste en dos bobinas dispuestas en un plástico de superingeniería llamado poliimida. Se aplica una corriente de impulsos a una bobina para generar un pequeño campo magnético local, que a su vez genera una corriente en la otra bobina.

Los aisladores digitales con aislamiento capacitivo consisten en un condensador con una fina capa aislante de dióxido de silicio (SiO2, sílice).

Características de los Aisladores Digitales

Los aisladores digitales tienen las siguientes características sobresalientes sobre los aisladores ópticos convencionales.

1. Gran Rigidez Dieléctrica

Los aisladores digitales se caracterizan por su gran rigidez dieléctrica. La rigidez dieléctrica de los aisladores ópticos oscila entre 1 y 20 Vrms/µm, mientras que la rigidez dieléctrica de los aisladores digitales con aislamiento magnético es de 300 Vrms/µm y de 500 Vrms/µm con aislamiento capacitivo, que es de 10 a 200 veces superior a la de los aisladores ópticos.

2. Alta Esperanza de Vida

Los aisladores digitales se caracterizan por su larga vida útil. Mientras que los aisladores ópticos tienen una esperanza de vida de unos 10 años, se dice que los aisladores digitales tienen una esperanza de vida de 25 años o más.

3. Alta Velocidad de Respuesta

Mientras que los aisladores ópticos pueden aislar señales de hasta unos 20 Mbps, los aisladores digitales pueden manejar velocidades de 150-200 Mbps, es decir, unas diez veces más rápidas.

4. Bajo Consumo de Corriente

Los aisladores digitales pueden mantener un bajo consumo de corriente. En particular, el tipo de aislamiento capacitivo puede reducir el consumo de corriente independientemente de la velocidad.

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Medidores Digitales de pH

投稿者作成者: 管理マスター
投稿日 2023年7月27日
Medidores Digitales de pH へのコメントはまだありません

¿Qué es un Medidor Digital de pH?

Un medidor digital de pH es un dispositivo de medición empleado para determinar el nivel de pH de una solución.

El término pH representa el potencial de hidrógeno o capacidad de hidrógeno y constituye una medida de la concentración de iones de hidrógeno en un líquido. Se expresa como un número en un rango de 0 a 14, con 7 representando neutralidad, valores por debajo de 7 indicando acidez y valores por encima de 7 denotando alcalinidad.

Un medidor digital de pH se emplea para leer de forma digital el índice de concentración de iones de hidrógeno en una solución. A veces, el pH también se abrevia como “pH” o “pH (potencial de hidrógeno)”.

Usos de los Medidores Digitales de pH

Los medidores digitales de pH se utilizan para mediciones medioambientales y análisis químicos. En la medición medioambiental, se utilizan para controlar la calidad del agua potable y las aguas residuales, y en el análisis químico, para el control de calidad en laboratorios y líneas de producción industrial.

En el análisis químico, el pH es un indicador que influye en la preparación de las muestras y en las condiciones de análisis. El pH también afecta al progreso de las reacciones químicas y, por lo tanto, es un elemento de control importante en la producción.

Principios de los Medidores Digitales de pH

El método de medición más utilizado en los medidores digitales de pH es el método del electrodo de vidrio. El método del electrodo de vidrio utiliza dos electrodos (electrodo de vidrio y electrodo de comparación). Cuando hay líquidos de pH diferente en las dos zonas separadas por las películas de vidrio de los electrodos, se genera una fuerza electromotriz correspondiente a la diferencia, y el pH se calcula midiendo el potencial de los electrodos de vidrio/comparación en el propio instrumento.

Hay que tener en cuenta que el pH-metro debe calibrarse antes de su utilización. Las soluciones patrón de pH se calibran generalmente con pH 7 como punto cero y una calibración de tres puntos con pH 4 y pH 9, pero la solución patrón de pH utilizada para la calibración puede modificarse en función del pH de la muestra. También hay que tener en cuenta que la pendiente de la curva de calibración se ve afectada por la temperatura.

La medición del pH en sí es una tarea sencilla, pero es importante conocer los puntos clave de la medición y disponer de un procedimiento de mantenimiento. Es importante disponer de un procedimiento para los puntos que deben medirse y los métodos de mantenimiento.

Otros métodos de medición del pH además del método del electrodo de vidrio incluyen el uso de indicadores como el papel tornasol, el método del electrodo de hidrógeno, el método del electrodo de quinhidrona y el método del electrodo de antimonio. No obstante, el método del electrodo de vidrio es más seguro, más preciso y más reproducible que los otros métodos de medición.

Más Información sobre Medidores Digitales de pH

1. Calibración de Medidores Digitales de pH

Calibrar un pH-metro significa ajustar correctamente los puntos cero y span (sensibilidad) del pH-metro utilizando una solución patrón de pH. Dado que existen operaciones específicas en función del medidor digitales de pH utilizado, las instrucciones proporcionadas deben tener prioridad sobre la calibración propiamente dicha.

La calibración puede realizarse como calibración de un punto utilizando un tipo de solución patrón de pH, calibración de dos puntos utilizando dos tipos o calibración de tres puntos utilizando tres tipos. La calibración de dos puntos suele utilizarse a menudo para calibrar los pH-metros. La calibración en un punto es una calibración simplificada. Para una calibración más rigurosa, se utiliza la calibración de tres puntos.

El valor real de la “fuerza electromotriz por pH” en el electrodo de vidrio se ve afectado por la contaminación de la película de vidrio y los “errores alcalinos” y “errores ácidos” (errores en condiciones fuertemente alcalinas y fuertemente ácidas, respectivamente). Por este motivo, suele ser inferior al valor teórico (59,16 mV a 25°C). El ‘pH7 EMF’ también se desvía del valor teórico (0 mV).

La medición previa y la calibración periódica garantizan mediciones de pH de gran precisión.

2. Soluciones de Calibración para Medidores Digitales de pH

Los tipos, la calidad y la composición de las soluciones patrón de pH son los siguientes:

Solución patrón de pH de oxalato
Solución de trihidrógeno dioxalato de potasio 0,05 mol/kg, pH 1,68 a 25 °C

Solución patrón de pH de ácido ftálico
0,05 mol/kg de hidrogenoftalato de potasio en solución acuosa, pH 4,01 a 25 °C

Solución patrón de pH de borato
0,01mol/kg de tetraborato sódico en solución acuosa, pH 9,18 a 25 °C

Solución patrón de pH de carbonato
0,025mol/kg de bicarbonato sódico y 0,025mol/kg de solución de carbonato sódico, a pH 10,02

Solución patrón de fosfato neutro
0,025mol/kg de hidrógeno fosfato potásico y 0,025mol/kg de solución de hidrógeno fosfato disódico, a pH 6,86 a 25°C

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Sodium Persulfate

What Is Sodium Persulfate?

Sodium persulfate, also known as sodium luoxodisulfate or sodium persulfate, is a substance with the molecular formula Na2S2O8.

Sodium persulfate has two types: peroxomonosulfate (molecular formula: H2SO5) and peroxodisulfate (molecular formula: H2S2O8), but the term sodium persulfate generally refers to the divalent sodium salt of peroxodisulfate. The CAS number 7775-27-1, which is a unique number for a chemical substance, is assigned to sodium persulfate. The molecular weight is 238.1 g/mol.

At room temperature and pressure, it exists in a white crystalline state and has a slightly pungent odor. Its solubility in water is 556 g/L at 20°C, but it is difficult to dissolve in ethanol and is easily degraded in ethanol. Aqueous solutions are neutral or slightly acidic. No boiling point or melting point is observed, and when heated, it decomposes at temperatures above approximately 180°C.

Uses of Sodium Persulfate

Sodium persulfate is used industrially for its use as a strong oxidizing agent. Specifically, it is used as a polymerization initiator for synthetic resins and fibers, as an etching agent for printed circuit boards, and as a surface treatment agent for metals.

Among these, it is most commonly used as a polymerization initiator for synthetic resins and as an initiator in radical polymerization reactions. Radical polymerization reaction is a type of polymerization reaction in polymer chemistry, in which polymer chains are elongated by radicals as reaction centers.

The decomposition of sodium persulfate produces sulfate radicals, which in turn draws hydrogen or electrons to initiate a chain polymerization reaction. This process yields polymers such as polyethylene, polyolefin, and polystyrene.

One application that has been attracting attention in recent years is the use in the oxidative decomposition of toxic substances. Examples include the decomposition of ammonia nitrogen, which causes eutrophication in wastewater, and decomposition of halogenated hydrocarbons, which are soil pollutants. Sodium Persulfate’s strong oxidizing power and the fact that the product of decomposition is sulfate ions, which are abundant in the natural environment, makes it suitable for these applications.

Properties of Sodium Persulfate

Sodium persulfate and other peroxo-sulfates are unstable and easily reduce themselves to generate sulfate oxides, which are oxidizing agents. They are unstable with respect to heat and temperature and decompose when heated, producing toxic and corrosive fumes (e.g., sulfur oxides).

It is also highly reactive, with strong flammable and reducing substances, metallic powders, and strong bases. When in contact or mixed with alcohol, it decomposes, separating the oxygen and producing sulfur dioxide, which is highly poisonous. Due to the nature of the oxygen produced during decomposition, it is not itself flammable, but it helps other substances to burn.

Other Information on Sodium Persulfate

Safety of Sodium Persulfate

In terms of safety for humans and animals, its oral toxicity is not high, being class 4 of the GHS classification, but it is highly irritating to the respiratory organs and skin due to its oxidizing power. In addition, decomposition products and mists containing decomposition products may be highly toxic. Therefore, appropriate protective equipment, including respiratory protection, must be worn during use, the storage environment must be prepared to prevent unexpected decomposition, and handling must be conducted in a manner that avoids mixing with other products.

From the viewpoint of preventing fires and explosions, they are oxidizing solids that help combustion when they come into contact with combustibles. In addition, it reacts violently with metals and reducing substances. Therefore, mixing with these substances must be avoided.

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Potassium Persulfate

What Is Potassium Persulfate?

Potassium persulfate is a sulfur oxoacid, a type of persulfate.

It is represented by the molecular formula K₂S₂O₈ and has a molecular weight of 270.32 g/mol. It is also known as potassium peroxodisulfate. The CAS number, which is a unique chemical number, is 7727-21-1.

It is generally known to be produced by the reaction of ammonium persulfate and potassium hydroxide in an aqueous solution, a process that is still used today. At normal temperature and pressure, it exists as a white to slightly light yellowish crystal state and is odorless.

Its solubility in water is 5.2g/100ml at 20℃, but it is soluble in hot water and almost insoluble in ethanol.

Uses of Potassium Persulfate

Potassium Persulfate is mainly used in the following applications:

Print etching agent
Metal surface treatment agent
Starch modifier
Polymerization initiator for synthetic resins and fibers
Soil conditioner
Bleaching agent for natural products
Synthetic oxidizers for pharmaceuticals

Etching agents for printed circuit boards are agents that corrode metals and metal oxides, and are mainly used as a surface treatment method to remove the surface of metals, glass, and semiconductors using their own corrosive properties. Etching is used not only in the manufacture of printed circuit boards but also in the processing of semiconductors and MEMS, because it can perform more precise processing in a batch than cutting or polishing.

Potassium persulfate is a powerful yet slow-reacting oxidant. It is still used today as a polymerization initiator in the synthesis of phenol, aromatic amines, and aromatic hydrocarbons. Potassium persulfate acts as an initiator in emulsion polymerization, an industrially important aqueous polymerization process.

Emulsion polymerization is a process in which insoluble monomers are mixed to form spherical micelles in a surfactant, which are then polymerized by heating with the addition of a polymerization initiator, such as potassium persulfate. This method is suitable for mass production in factories because it eliminates the heat generated during the polymerization reaction and keeps the viscosity of the system low.

Potassium persulfate is used in oxygen bleaches to bleach and clean natural products. Because it is a strong base, oxygen bleach is highly resistant to yellowing caused by grease and sebum.

Properties of Potassium Persulfate

Potassium Persulfate, when mixed with combustibles or organic materials, it decomposes by heat, impact, or friction and acts as a strong oxidizer that causes severe combustion.

When heated, it decomposes to produce sulfurous acid gas, which is gaseous sulfur dioxide. Sulfurous acid gas is a colorless, toxic gas with a pungent odor.

Inhalation of sulfurous acid gas can cause severe irritation to the respiratory system and may cause asthma. It also has the property of reacting violently with strong bases. In terms of stability, it should be prevented from exposure to high temperatures, direct sunlight, heat, and static electricity, as it may be altered by light.

Other Information on Potassium Persulfate

Handling and Storage Precautions

When handling or storing potassium persulfate, the following precautions should be taken:

Avoid contact with combustibles and reducing agents.
Do not use high-temperature materials in the vicinity.
The storage area should have fire-resistant walls, columns, and floors, and the beams should be made of noncombustible materials.
Roofs of storage areas should be made of noncombustible materials and should not have ceilings.
Store containers tightly closed in a cool, well ventilated, light-shielded area.

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Thallium Sulfate

What Is Thallium Sulfate?

Thallium sulfate is the sulfate salt of thallium.

It is a colorless crystalline powder with no taste or odor. It is soluble in water and ethanol and is also used in liquid form.

Thallium sulfate is classified as a deleterious substance and must be stored and used with care. It has acute and chronic toxicity, affecting the gastrointestinal tract, nervous system, respiratory organs, and kidneys when ingested orally.

It has also been shown to be toxic for reproduction, and may affect the development of testes and fetuses. Because of these toxic effects, thallium sulfate was used as a rat poison, but is no longer used.

Uses of Thallium Sulfate

Thallium sulfate was once used as a rat poison. Because it is soluble in water, it is easy to prepare poison baits, and since rats eat it without avoiding it, poison baits were prepared by adding a solution of thallium sulfate to the food preferred by rats.

Thallium sulfate is not excreted but accumulates in the body of rats, so even if an individual does not eat a lethal dose at once, it will die by continuous ingestion of the poisoned food. In addition, its reproductive toxicity suppresses the reproduction of rats and keeps the population low over the long term.

Rodenticides containing thallium sulfate were previously registered as pesticides, but the registration was revoked due to its high toxicity and low distribution volume. Since the pesticide registration of thallium sulfate expired, other ingredients such as zinc phosphide, coumarin, and difethialol have been used in rodenticides.

Characteristics of Thallium Sulfate

Thallium sulfate is the sulfate salt of thallium, with the chemical formula Tl2SO4. Thallium sulfate is a colorless crystal that is stable at room temperature, and when dissolved in water, it ionizes into thallium (univalent) and sulfate ions.

The raw material thallium is a group 13 metallic element that is recovered as a byproduct of the refining process of copper, lead, and zinc. Thallium exists mainly as a monovalent ion, but when oxidized, trivalent ions may be produced to form thallium oxide, etc.

The basic properties of thallium sulfate (molecular weight, specific gravity, and solubility) are as follows:

Molecular weight: 504.83
Specific gravity: 6.77
Solubility: Soluble in water (4.87 g/100 mL at 20°C)

Other Information on Thallium Sulfate

1. Toxicity to Humans

Thallium sulfate is toxic to humans. Ingestion due to accidents or incidents in the past has been reported to cause anorexia, vomiting, abdominal pain, bloody stools, etc., followed by abnormal limb perception, hallucinations, convulsions, tachycardia, hair loss, and other symptoms. In severe cases, death occurs due to kidney and central nervous system abnormalities and heart failure.

To prevent accidental ingestion, containers containing thallium sulfate must be clearly labeled with the name of the substance. Storing thallium sulfate in containers such as those used for food or handling it while eating or drinking increases the risk of accidental ingestion or ingestion and is very dangerous.

Since experiments on rats have confirmed that the original (unformulated pure product) of thallium sulfate is also percutaneous toxic, care must also be taken to avoid skin contact. Wear protective equipment such as nitrile gloves and protective glasses, and wash thoroughly with water if it adheres to the skin. If it gets into the eyes, rinse well under running water and seek medical attention.

2. Decomposition by Heating and Oxidation

When thallium sulfate is heated, it decomposes to produce fumes such as toxic thallium and sulfur oxides. Fumes are fine particles of evaporated or sublimated substances that condense in the air. Fumes are spread over a wide area as smoke or aerosols, so there is a risk of inhalation by workers. Thallium sulfate is also toxic in fumes, so if there is a risk that thallium sulfate may be heated in experiments, etc., measures such as handling it with ventilation in a draft are necessary.

Thallium sulfate reacts violently with oxidants to form oxides. The reaction heat during oxidation may produce toxic fumes, so care should be taken to store and use thallium sulfate in such a way that it does not come into contact with oxidants.

4. Environmental Impact

Thallium sulfate is toxic to wild birds and aquatic organisms, and must be prevented from leaking into the environment. When disposing of thallium sulfate, follow the standards set by the local government or outsource disposal to a specialized contractor.

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Zinc Sulfide

What Is Zinc Sulfide?

Zinc Sulfide

Zinc sulfide is a sulfide of zinc represented by the chemical formula ZnS.

Zinc sulfide is a white or yellow powder or crystal with a density of 4.0 g/cm3, a melting point of 1,718°C, and a sublimation point of 1,180°C. It occurs naturally as sphalerite or zinc-blende and rarely as wurtzite.

Generally, it exists as a stable cubic form and is produced as sphalerite. The hexagonal form is obtained synthetically, but also occurs naturally as wurtzite.

Uses of Zinc Sulfide

Zinc sulfide is used as a raw material for phosphors, paints, rubber pigments, lithopons, leather, dental rubber, X-ray screens, and semiconductor laser crystal materials. Zinc sulfide with appropriate impurities has long been used as a silicophore because it emits silica light when irradiated with ultraviolet light.

The color of the light emitted can be changed depending on the type of impurity, and because it also emits light when exposed to an electron beam, it is applied to the silica-light surface of cathode-ray tubes in televisions and other equipment. When mixed with small amounts of radium or thorium, it is also used as a luminous paint for watches.

Properties of Zinc Sulfide

When Zinc sulfide is moist, it is gradually oxidized in air to zinc sulfate. Zinc sulfide is insoluble in water and alkalis and soluble in mineral acids. Newly made zinc sulfide is soluble in acids.

Naturally occurring sphalerites and wurtzites are semiconductors with large intrinsic band gaps; the band gap values at 300 K are 3.91 eV for wurtzites and 3.54 eV for sphalerites.

Zinc sulfide is a covalent compound with the composition ZnS. At approximately 1,293 K, a transition from a zinc sphalerite-type to a wurtzite-type crystal structure occurs. The melting point of the sphalerite form of Zinc sulfide is 1,991 K. The standard enthalpy of formation at 298 K is -204.6 kJ/mol.

Other Information on Zinc Sulfide

1. Synthesis of Zinc Sulfide

Zinc sulfide is produced by the direct compounding of sulfur and zinc. Zinc sulfide can also be obtained by blowing hydrogen sulfide into an aqueous solution containing zinc ions.

2. Zinc Sulfide in Atomic Physics

In early atomic physics, Ernest Rutherford and his colleagues used zinc sulfide as a scintillator, a phosphor material. Zinc sulfide emits light when excited by radiation such as alpha rays, X-rays, and electron beams. Zinc sulfide is therefore useful as a sensitizer for X-rays and as a material for cathode ray tubes. In the presence of impurities, it becomes phosphorescent and emits blue light and ultraviolet light.

Since automatic measurement was difficult with the technology of the time, Rutherford et al. used zinc sulfide powder to count the luminescence by eye in a dark room. They proved the existence of nuclei by applying the technique to the experiment of Rutherford scattering, in which alpha rays are irradiated onto a material. Zinc sulfide is still useful as an element for alpha-ray detection.

3. Zinc Sulfide as a Light-Storing Agent

Zinc sulfide can be used as a phosphorescent agent. Adding a few ppm of activator makes it useful for cathode ray tubes and X-ray screens, as well as for components that glow in the dark. For example, the light emitted will be bright blue when silver is used as an activator and yellow when manganese is used.

A well-known phosphorescent agent is copper, which emits light for a long time and has a greenish color. Zinc sulfide doped with copper is also used in electroluminescence panels.

4. Other Applications of Zinc Sulfide

Zinc sulfide is also used as an optical element for infrared light. It transmits visible light to wavelengths above 12 μm and can be used as flat optical windows or lenses.

Furthermore, it can be used as both a P-type and N-type semiconductor through doping, an unusual property for a group II-VI semiconductor.

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Manganese Sulfide

What Is Manganese Sulfide?

Manganese sulfide is a compound of manganese and sulfur.

It occurs in minerals such as alabandite and rambergit. Manganese sulfide is generally found in the monosulfide or disulfide state. In addition, Manganese Sulfide (II) has three transformations: α, β, and γ.

A similar name is manganese sulfate, but it is a completely different compound with or without oxygen.

Uses of Manganese Sulfide

Manganese sulfide is mainly used as an additive to improve the machinability of sintered parts in the field of powder metallurgy.

Powder metallurgy is a manufacturing process in which metal powders are formed and sintered to produce metal products. Small motor parts for washing machines, fans, hard disks, etc. are examples of products processed by this powder metallurgy process.

Properties of Manganese Sulfide

Manganese Sulfide (II) Alpha Form
It is a green cubic crystal. Its melting point is 1,620℃ and it is antiferromagnetic.
Manganese Sulfide (II) Beta Form
Red cubic crystal
Manganese Sulfide (II) Gamma Form
Pale red cubic crystal. p-type semiconductor at 700℃.

Among manganese sulfide (II), β- and γ-forms are unstable. The β and γ forms are unstable in manganous manganese sulfide (II) and are quickly oxidized to the α form. When used in powder metallurgy, the stable α-form is used.

Manganese sulfide (IV), on the other hand, is a blackish-brown cubic crystal. It is anti-ferromagnetic.

Structure of Manganese Sulfide

Manganese sulfide (II) has the chemical formula MnS and a molecular weight of 87.00. The alpha form of manganese sulfide (II) has a sodium chloride type structure with a Mn-S distance of 0.261 nm and a density of 4.05 g/cm3.

The beta form of Manganese Sulfide (II) has a zinc shear zinc ore type structure with a Mn-S distance of 0.243 nm and a density of 3.27 g/cm3.

Manganese sulfide (II) has a wurtzite-type structure with a Mn-S distance of 0.241 nm and a density of 3.26 g/cm3.

On the other hand, manganese sulfide (IV) has the chemical formula MnS2, with a molecular weight of 119.07. It has a pyrite-type structure. Its density is 3.463 g/cm3, Mn-S distance is 0.259 nm, and S-S distance is 0.209 nm.

Other Information on Manganese Sulfide

1. How Manganese Sulfide (II) Is Produced

Manganese sulfide (II) is also called manganese monosulfide. The alpha form of manganese sulfide (II) occurs naturally as sphalerite. Manganese sphalerite is a mineral that contains cubic manganese (II) sulfide.

Sphalerite is also called manganite sulfide or arabite. The alpha form of Manganese Sulfide (II) can be obtained by boiling an aqueous solution of manganese (II) chloride in the presence of a small amount of potassium oxalate, adding a slight excess of ammonia water, and passing hydrogen sulfide through it. The beta form of manganese sulfide (II) can be formed by passing hydrogen sulfide through an aqueous solution of manganese (II) acetate when cold.

The gamma form of manganese sulfide (II) can be obtained as a precipitate by boiling an aqueous solution of manganese chloride (II), adding ammonium chloride, and passing hydrogen sulfide through the solution while adding ammonia water.

2. Method of Producing Manganese Sulfide (Iv)

Manganese sulfide (IV) is also called manganese disulfide. It occurs naturally as a hauerite. Manganese sulfide (IV) can be obtained by adding sulfur and potassium polysulfide to an aqueous solution of manganese (II) sulfate and heating in a sealed tube.

When heated, manganese sulfide (IV) decomposes to release sulfur. Manganese sulfide (IV) reacts with hydrochloric acid to form manganese chloride (II).

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Silicon Tetrachloride

What Is Silicon Tetrachloride?

Silicon tetrachloride is an inorganic compound consisting of silicon (Si) bonded with four chlorines.

It is also known as silicon chloride, silicon tetrachloride, tetrachlorosilane, and silicon tetrachloride. Although silicon tetrachloride exists as a liquid at room temperature, it quickly volatilizes upon heating due to its low boiling point of 57.6°C.

Uses of Silicon Tetrachloride

Silicon tetrachloride is rarely used in its raw state. It is basically used as a raw material for other silicon compounds.

1. High-Purity Silicon Tetrachloride

It is used as a raw material for silicon single crystals, for epitaxial growth of silicon wafers, for etching gas and other semiconductor fields, for synthetic quartz, and for synthetic quartz glass. Synthetic quartz glass has high purity and low metallic impurities. Besides, it allows light to pass through well and is resistant to heat, so it is used in photomasks for optical fibers and semiconductors.

2. General-Purity Silicon Tetrachloride

It is used as a raw material for silicon oxide (silica), which is used as a reinforcing filler for resins, CMP slurry for semiconductor polishing, adhesives, and viscosity adjusters for paints. It is also used as a raw material for various organic silicones (silane coupling agents, silicone resins, etc.).

Characteristics of Silicon Tetrachloride

The molecular formula of silicon tetrachloride is SiCl4, and its molecular weight is 169.89. It has a specific gravity of 1.52, a melting point of -70°C, and a boiling point of 57.6°C. At room temperature and pressure, it is a colorless, viscous liquid. It also has a pungent odor that can be suffocating. It is soluble in ether, benzene, chloroform, and carbon tetrachloride.

It reacts violently with water, strong oxidizers, strong acids, alcohols, bases, ketones, and aldehydes to form toxic and corrosive hydrogen chloride (HCl). In humid air, it hydrolyzes instantly to produce white smoke containing chlorine gas.

In the presence of water, the hydrochloric acid produced by hydrolysis corrodes many metals. For this reason, the metals that can be used are limited to nickel steel and copper-nickel alloys. Polyethylene, polyvinyl chloride, and Teflon can be used as resins.

Other Information on Silicon Tetrachloride

1. How Silicon Tetrachloride Is Produced

It is produced by heating silicon metal and chlorine or hydrogen chloride, or by chlorinating calcium silicide or other materials. Raw materials of a purity corresponding to the product purity required must be used.

Chlorination of metallic silicon: Si + 4HCl → SiCl4 + 2H2
Chlorination of calcium silicide: CaSi2 + 5Cl2 → 2SiCl4 + CaCl2

Research has also been reported on the production of Silicon Tetrachloride from silicate biomass such as rice chaff and rice straw.

2. Safety of Silicon Tetrachloride

Handling
Silicon tetrachloride is a severe irritant when adhered to skin and mucous membranes, and may cause erythema, edema, severe conjunctivitis, and coughing. When handling, wear a protective mask, impervious protective gloves, protective glasses with side plates, and long-sleeved work clothes.

In the event of a fire, heat, flames, and water used to extinguish the fire will generate hydrogen chloride gas, which is corrosive and highly toxic, and will emit very thick smoke, so care should be taken. If there is no danger, it is recommended to take measures such as moving the container away from the fire location.

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Polyvinyl Alcohol

What Is Polyvinyl Alcohol?

Polyvinyl alcohol is a type of water-soluble synthetic resin.

It was invented in Germany in 1924. It was invented in Germany in 1924 and has since been industrially developed by Japanese companies.

Polyvinyl Alcohol Manufacturing Process

Polyvinyl alcohol, the monomer of polyvinyl alcohol, cannot exist as a monomer because it is isomerized to the more stable acetaldehyde. Polyvinyl alcohol is therefore synthesized via polyvinyl acetate.

Industrially, vinyl acetate is synthesized from petroleum-derived ethylene, acetic acid, and oxygen. Palladium catalysts are used in this reaction.

Polyvinyl acetate is obtained by addition polymerization of the vinyl acetate. Polyvinyl alcohol is then synthesized by hydrolyzing polyvinyl acetate.

Properties of Polyvinyl Alcohol

Polyvinyl alcohol exists as a solid at room temperature and is soluble in warm water. This feature of solubility in warm water is unique among synthetic resins. This feature is due to the large amount of hydrophilic hydroxy groups (-OH groups) in the molecule.

This polyvinyl alcohol has properties, such as adhesion to hydrophilic surfaces, film formation, and viscosity.

It is also a stable polymer that does not easily change or deteriorate in various environments, making it an easy substance to handle over the long term. It has chemical resistance and dissolves only in special solvents such as dimethyl sulfoxide and water. It has almost no skin irritation, eye irritation, or skin sensitization, making it a safe substance for the human body.

Uses of Polyvinyl Alcohol

Polyvinyl alcohol is used in a wide variety of applications due to its properties.

Taking advantage of its water solubility and adhesive properties, it is used in cosmetics and as an adhesive or sizing agent.

When used in cosmetics, it is used for film formation and emulsion stabilization. By forming a film, liquid products such as foundation and mascara become a soft film and stay on the skin more easily.

When formulated as an adhesive, it is also used as a substance that serves as an adhesive as it is, and is often sold in the form of liquid glue. It is also used as a glue for the backs of stamps. It is also used as a synthetic laundry glue as a glue agent.

It is also used as a base material for polarizing plates used in liquid crystal displays. It is also used as a raw material for the synthetic fiber vinylon.