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

결정화(Crystallization)는 냉각 포화 용액(cooling saturated solution)과 같은 공급원에서 결정이 형성되는 상 변형 과정입니다.
결정화는 1차 핵형성으로 시작되며, 이는 프로세스를 돕기 위해 기존 결정이 없는 투명한 용액에서 시작됩니다. 그것은 동종 유형과 이종 유형으로 나뉩니다.
이질적인 핵형성(nucleation) 동안, 결정은 먼지 입자와 같은 핵형성 표면에 형성됩니다. 대조적으로, 균질한 핵형성은 이질적인 미립자 없이 투명한 용액에서 발생합니다.
2차 핵형성 동안, 성장은 파종(seeding)을 통해 도입된 것과 같은 모결정(parent crystal)으로 인해 발생합니다.
임계 클러스터 크기에 도달한 핵 생성 클러스터는 성장하여 더 큰 결정을 형성하는 반면, 반경이 더 작은 클러스터는 용해를 겪습니다.
결정 성장은 용매 내 용질의 농도와 용해도의 비율 또는 과포화 비율 S가 1을 초과할 때 발생합니다. 용매 증발을 통해 용질 농도를 높이거나 온도를 낮춰 용질의 용해도를 낮추면 S 값이 증가합니다.
결정화는 일반적으로 활성 제약 성분을 제조하는 데 사용됩니다.

결정 성장: 결정화의 원리

Crystal Growth: Principles of Crystallization

결정화는 결정이 과포화 용액에서 침전되거나 다른 소스에서 형성되는 상 변환 과정입니다. 결정화 과정에서 원자나 분자는 에너지를 최소화하기 위해 명확하고 견고한 결정 격자로 배열됩니다.

결정화를 시작하려면 용질의 농도와 용액의 온도를 조작해야 합니다. 결정 성장은 용매 내 용질의 농도와 용해도 비율(과포화 비율, S)이 1을 초과할 때 발생하므로 용액은 농축되어야 하며 온도는 충분히 낮아야 합니다. 결정화가 활발하게 일어나기 때문에 용매 증발을 통해 용질의 농도를 높이거나 온도를 낮추어 용질의 용해도를 낮추면 S 값이 증가하여 공정에 도움이 됩니다. 결정 성장의 또 다른 중요한 요소는 결정의 크기와 형태에 필수적인 역할을 하는 냉각 속도입니다. 천천히 냉각하면 더 큰 결정이 생성되고, 급속 냉각하면 작은 결정이 생성됩니다.

결정화의 물리적 과정에는 핵형성과 결정 성장이라는 두 단계가 포함됩니다. 핵 생성 중에 용매는 용질 분자의 무작위 축적을 시작하여 궁극적으로 핵 또는 시드라고 불리는 첫 번째 결정을 형성하는 클러스터를 형성합니다. 기존 결정이 전혀 포함되지 않은 용액에서 결정 핵이 형성되는 경우 이를 1차 핵생성이라고 합니다. 1차 핵형성은 동종 또는 이종 메커니즘을 통해 발생합니다. 불균일 핵생성 동안 결정은 먼지 입자와 같은 계면활성제에 형성됩니다. 반면, 균일한 핵형성은 이종 입자가 없는 투명한 용액에서 발생합니다. 2차 핵형성에서는 씨딩을 통해 도입된 것과 같은 모결정에서 성장이 발생합니다. 결정화의 두 번째 단계(결정 성장) 동안 점점 더 많은 용질 분자가 종자의 단단한 격자 구조에 합류하여 결국 결정 크기가 거시적 규모로 증가합니다. 결정이 형성되고 용액이 실온으로 냉각되면 용액을 진공 여과를 사용하여 여과하고 분리된 결정을 건조하여 보관합니다.

결정화는 제약 및 화학 산업에서 분리 및 정제 단계로 자주 사용됩니다. 또한 설탕, 소금, 인공 감미료 및 기타 결정질 조미료를 제조하기 위해 식품 산업에서 자주 사용됩니다.

결정화(crystallization)는 결정이 과포화 용액에서 침전되거나 다른 공급원에서 형성되는 상 변형 과정입니다. 동안...

crystal-growth-principles-of-crystallization

Education

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JoVE Core

Analytical Chemistry

분석 화학

Unit 1

제1단원

Introduction to Separation Methods

분리 방법 입문

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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

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sublimation

Sublimation in Separation and Purification

Sublimation is the direct change of a solid into a gas. It skips the liquid state. A common example is solid carbon dioxide, or dry ice, which turns into gaseous carbon dioxide at standard pressure and room temperature. The phase diagram shows when sublimation can happen. This process occurs at the solid-gas boundary. It is not seen above the triple point of a substance. The reverse process is deposition, which is when a gas changes directly into a solid. Sublimation and deposition can help...

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...

electrodeposition

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

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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

Ion exchange chromatography separates charged molecules from a solution by swapping them with mobile, or active, ions on a stationary phase. It is used to separate ions, soften and deionize water, and purify solutions. The method depends on a solid column made of high-molecular-weight, chemically stable polymers that are crosslinked to make them porous and essentially insoluble. These polymers are functionalized with either acidic or basic groups. When acidic groups are present, the resin is a...

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

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Crystal Formation Through Supersaturation

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