Name: crystal formation through supersaturation
Uploaded: 2025-05-22T09:05:36.000Z
Duration: 1 min 25 s
Channel: JoVE

結晶化は、冷却飽和溶液のような源から結晶が形成される相変態プロセスです。
結晶化は一次核形成から始まり、このプロセスを支援するための既存の結晶を含まない透明な溶液から始まります。それは均質なタイプと異質なタイプに分けられます。
不均一核形成中、結晶はダスト粒子のように核形成面に形成されます。対照的に、均質な核形成は、不均一な粒子を含まない透明な溶液中で行われます。
二次核形成では、播種によって導入されるような親結晶によって成長が起こります。
臨界クラスターサイズに達した核クラスターは成長してより大きな結晶を形成しますが、半径が小さいクラスターは溶解します。
結晶成長は、溶媒中の溶質の濃度と溶解度の比率、または過飽和比Sが1を超えると発生します。 溶媒の蒸発によって溶質濃度を上げるか、温度を下げることによって溶質の溶解度を下げると、Sの値が増加します。
結晶化は、医薬品有効成分の製造に一般的に使用されます。

結晶成長: 結晶化の原理

Crystal Growth: Principles of Crystallization

結晶化は、結晶が過飽和溶液から沈殿するか、他のソースから形成される相変化プロセスです。結晶化中、原子または分子は、エネルギーを最小限に抑えるために、明確に定義された硬い結晶格子に配置されます。

結晶化を開始するには、溶質の濃度と溶液の温度を操作します。結晶成長は溶媒中の溶質の濃度と溶解度の比、つまり過飽和比 S が 1 を超えるときに発生するため、溶液を濃縮し、温度を十分に低くする必要があります。結晶化が活発に起こるため、溶媒の蒸発によって溶質の濃度が増加するか、温度を下げて溶質の溶解度が減少すると、S の値が増加し、プロセスが促進されます。結晶成長におけるもう 1 つの重要な要素は冷却速度です。これは結晶のサイズと形態に重要な役割を果たします。ゆっくりと冷却すると大きな結晶が生成されますが、急速に冷却すると小さな結晶が生成します。

結晶化の物理的プロセスには、核生成と結晶成長という 2 つのステップが含まれます。核形成中、溶媒は溶質分子のランダムな蓄積を開始し、最終的に核または種と呼ばれる最初の結晶を形成するクラスターを形成します。既存の結晶を含まない溶液から結晶核が形成される場合、それらは一次核生成と呼ばれます。一次核形成は、均一または不均一のメカニズムを通じて発生します。不均一核形成では、塵粒子のような異物の表面で結晶が形成されます。一方、均一な核生成は、不均一な粒子のない透明な溶液中で起こります。二次核形成では、種まきによって導入されたような親結晶から成長が起こります。結晶化の第 2 段階 (結晶成長) では、シードの結晶格子構造にますます多くの溶質分子が結合し、最終的には結晶サイズが巨視的なスケールにまで増大します。結晶が形成され、溶液が室温まで冷却されたら、真空濾過を使用して溶液を濾過し、分離した結晶を乾燥して保管します。

結晶化は、製薬業界や化学業界の分離および精製ステップとしてよく使用されます。また、食品業界では、砂糖、塩、人工甘味料、その他の結晶調味料の製造にも頻繁に使用されています。

結晶化は、結晶が過飽和溶液から沈殿するか、他の供給源から形成される相変態プロセスです。中。。。

crystal-growth-principles-of-crystallization

Education

JoVE Core

Analytical Chemistry

分析化学

Unit 1

ユニット1

Introduction to Separation Methods

分離手法概論

KEY TERMS AND CONCEPTS

重要用語と概念

crystal formation through supersaturation

Crystal formation through supersaturation begins when a solution contains more dissolved solute than it can normally hold. In crystallization, atoms or molecules line up into a rigid crystal lattice so the system can lower its energy. To start the process, the solute concentration and the solution temperature must be adjusted so the supersaturation ratio, S, is greater than one.

Supersaturation can be increased in two main ways. One method is to concentrate the solution by evaporating the solvent. Another method is to lower the temperature, which reduces the solubility of the solute. Cooling rate also matters. Slow cooling usually produces larger crystals, while rapid cooling tends to form smaller ones.

Crystallization happens in two stages: nucleation and crystal growth. During nucleation, solute molecules gather into small clusters until the first crystal, called the nucleus or seed, appears. If the nuclei form in a solution with no pre-existing crystals, the process is primary nucleation. Primary nucleation can be homogeneous in a clear solution or heterogeneous on particles such as dust.

In secondary nucleation, growth begins from parent crystals, such as those added during seeding. During the crystal growth stage, more solute molecules attach to the rigid lattice of the seed, making the crystal larger. After the crystals form and the solution returns to room temperature, the mixture is filtered by vacuum filtration. The crystals are then dried and stored.

This separation method is widely used in the pharmaceutical and chemical industries. It also has major uses in the food industry. Sugar, salt, artificial sweeteners, and other crystalline seasonings are often made this way.

Crystal Formation Through Supersaturation

crystal-formation-through-supersaturation

states of matter and phase changes

Heating and Cooling During Phase Changes

Heating and cooling can change a substance from one state of matter to another. These phase changes depend on internal energy, which is the total kinetic energy of particles and the potential energy from their interactions. In the condensed phases, stronger intermolecular forces and the pressure on the substance affect that internal energy. The internal energy is highest in the gaseous state, lowest in the solid state, and in between for the liquid state. Phase transitions happen when...

distillation: vapor&ndash;liquid equilibria

Distillation and Boiling Point Changes

Distillation separates a miscible liquid mixture by using differences in boiling points. It works best when the two liquids have a significant boiling point gap, usually at least 20°C. In this process, the mixture is heated until the more volatile component reaches its bubble point and begins to vaporize. The vapor then rises into a condenser. A condenser is a glass tube with separate inner and outer sections. Cold water flows through the outer section and cools the vapor in the inner section,...

filtration

Filtration Setup and Filtrate Collection

Filtration separates a solid from a liquid by passing a suspension through a porous medium. The solid stays on the filter, and the liquid, called the filtrate, passes through. This makes filtration a physical separation process, not a chemical change. The filtering medium is chosen for the purpose of the separation, the amount of material, and the nature of the precipitate. A good filter medium should be inert, mechanically strong, nonabsorbent toward dissolved materials, and able to let...

centrifugation

Centrifugation for Separating Particles

Centrifugation separates particles in a liquid by using differences in size and density. The sample is placed in centrifugation tubes and spun at high angular velocity. This creates centrifugal force, which makes the different components move at different rates. After spinning, the supernatant, or liquid above the settled material, is decanted. In some cases, the pellet is kept for further purification. In other cases, the supernatant is kept and may be spun again for additional processing. <br...

sublimation

Sublimation in Separation and Purification

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recrystallization: solid&ndash;solution equilibria

recrystallization-solidsolution-equilibria

Recrystallization for Purifying Solid Compounds

Recrystallization is a way to purify solid compounds by using differences in solubility. It does not involve a chemical reaction. Instead, it relies on physical properties of the desired compound and the impurities. The process is based on solid-solution equilibrium, also called solubility equilibrium. In this equilibrium, a component is split between the solid phase and the solution phase. At equilibrium, the chemical potential of that component is the same in both phases. To begin...

crystal growth: principles of crystallization

Crystal formation through supersaturation begins when a solution contains more dissolved solute than it can normally hold. In crystallization, atoms or molecules line up into a rigid crystal lattice so the system can lower its energy. To start the process, the solute concentration and the solution temperature must be adjusted so the supersaturation ratio, S, is greater than one. Supersaturation can be increased in two main ways. One method is to concentrate the solution by evaporating the...

precipitation and co-precipitation

Selective Ion Separation by Precipitation

Selective ion separation by precipitation is used to isolate ions from a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent can be separated by using differences in their solubility products. A solubility product is the limit at which an ionic solid begins to form from dissolved ions. One example is the separation of Cu(II) and Fe(II) ions as insoluble sulfides. Copper(II) sulfide is first precipitated by adding acidic H2S. The acid...

coagulation

Wastewater Cleanup by Coagulation

Coagulation helps remove colloidal particles from wastewater. Colloids are tiny solid particles suspended in a liquid. They are usually negatively charged, so they attract a compact first layer of positive ions. More counterions gather around them and form an electrical double layer. This charge barrier keeps the particles apart and stabilizes the colloid. These suspended solids can be a problem because they may contain toxins that are hard to remove. Coagulation is used to make the particles...

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Electrodeposition for Metal Ion Separation

Electrodeposition separates metal ions from a solution by using an electric current and an electrolytic cell. The cell has an anode and a cathode. When current flows, oxidation happens at the anode. At the cathode, metal ions gain electrons, undergo reduction, and deposit on the large metal surface. This method works well when metals have very different reduction potentials. Copper and nickel in the same solution can be separated this way. First, the solution is made acidic. Then current is...

extraction: partition and distribution coefficients

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Solvent Partitioning in Chemical Extraction

Solvent partitioning in chemical extraction describes how a solute spreads between two immiscible solvents. Immiscible solvents do not mix, such as an aqueous phase and an organic phase. The distribution law, also called Nernst's distribution law or the partition law, explains how that solute is shared at a constant temperature and equilibrium. At equilibrium, the ratio of solute concentrations in the two solvents stays constant. For extraction from water into an organic solvent, this...

extraction: effects of ph

pH Control in Liquid Extraction

pH control in liquid extraction changes how amines and acids move between organic and aqueous phases. The pH of the aqueous phase affects the charge on acidic and basic solutes. The charged form is usually more soluble in the aqueous phase. For a weak base such as an amine, the neutral form is called B. Its partition coefficient, K, describes how the neutral molecule distributes between the two liquids. If the conjugate acid of the amine is soluble only in the aqueous phase, while the base...

extraction: advanced methods

Chelate Extraction for Metal Ion Separation

Chelate extraction is a way to separate metal ions by using an organic ligand, or chelating agent, to form an uncharged metal complex. The chelating agent needs hydrophobic groups, and it must act as a weak acid so it can lose a proton and bind to the metal. Most organic ligands used for this method are not stable in water or are insoluble in the aqueous phase. For that reason, the chelating agent is first placed in the organic phase. It then moves into the aqueous phase, where the...

chromatography: introduction

Chromatography: Separation by Polarity

Chromatography separates compounds by how they divide between a stationary phase and a mobile phase. The stationary phase is the material that holds the compounds for a time. The mobile phase is the solvent that carries the solutes to be analyzed. In column chromatography, a mixture flows through the stationary phase. The compounds separate based on their structure and polarity. Solutes that interact weakly with the stationary phase move faster through the column and exit first. Solutes that...

dialysis

Dialysis Separation by Diffusion

Dialysis separates small molecules from larger ones by diffusion through a semipermeable membrane. It is a purification method used to remove unwanted ions or small organic molecules from a sample while keeping larger analytes in place. The membrane is usually made of cellulose acetate or cellulose nitrate. Its pores are typically about 1 to 5 nm wide. Molecules such as chloride, sodium, and glucose can pass through these pores. Larger molecules, including proteins, hormones, and enzymes, are...

volatilization

Mass Loss in Gravimetric Analysis

Volatilization gravimetry is a way to measure mass loss in a sample by driving off a volatile substance. It helps estimate how much volatile material is present. In this method, a known amount of sample is heated to a high temperature in a crucible or another suitable vessel. As the sample heats, the volatile substance evaporates. The vapor is then completely removed from the crucible, either by continued heating or by bubbling an inert gas through the vessel. The non-volatile part stays...

ion exchange

Ion Exchange Resins and Charged Molecules

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key terms and concepts

Learn how supersaturation, cooling rate, nucleation, and crystal growth shape crystal formation, and why crystallization is used to separate and purify materials.

Crystal Formation Through Supersaturation | JoVE K12

JoVE Core 分析化学 は、複雑な化学原理をアニメーションで視覚化することで、SI 単位から NMR 分光法を含むトピックをよりわかりやすくします。実験を撮影した実写動画では、これらの概念が世界中の研究所でどのように応用されているかを取り上げています。

analytical chemistry

Crystal Formation Through Supersaturation

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