Not much Explanation: As you know, crystallization is an important step in purification. I have written four paragraphs for a simple question! I am not going to win prizes for brevity. Related questions How are saturated solutions at equilibrium? How are supersaturated solutions prepared? How can you identify a saturated solution?
How do supersaturated solutions demonstrate conservation of energy? How do you make saturated solution of potassium iodide? How do you make saturated solution of sodium bicarbonate? The choice of words is therefore always ambiguous, but in general the IUPAC nomenclature should be followed where appropriate eg. To answer the other part of your question about chemical vs. Both are physical changes. Technically, ions in solution are something totally different than ions in a crystal lattice, but especially for organic chemicals the difference is neglegible if present at all.
The terms are not really clearly defined and there is a big grey area in the middle where both can apply. But in general, one would speak of crystallisation if it is a slow process that mainly happens at the bottom of the solution and yields something with a defined crystal structure. Precipitation would be a process which can happen throughout the entire solution rather quickly and tends to result in something cloudy, ill-defined.
So in the case of adding a chloride solution to one of silver nitrate, when silver chloride is formed immediately and almost quantitatively as a cloundy substance everywhere where there are chloride ions, one would not call it crystallisation but precipitation.
On the other hand, if I dissolve copper sulphate in water and let it stand at cold temperatures for a long time to generate large single crystals, I would speak of crystallisation and deem precipitation to be wrong. An example for the grey area would be the removal of triphenyl phosphane from a solution in dichloromethane or ether by adding hexanes. The precipitate forms rather fast, especially if the more polar solvent is evaporated, but at the same time it is rather crystalline looking I have no clue if they are actually crystals or just look nice.
I have heard both crystallisation and precipitation in this context. Crystallisation is formed from a super saturated solution while precipitation is formed due to reaction of 2 substances to form sparingly soluble product.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Difference between precipitation and crystallisation Ask Question. Asked 6 years, 1 month ago. The controlled conditions of sonocrystallization allow for reproducibility.
All results achieved in small scale, can be up-scaled completely linear. Ultrasonic crystallization and precipitation enable for the sophisticated production of crystalline nano-particles — in both, lab and industrial scale.
Those bubbles grow over several cycles until they cannot absorp more energy so that they collapse violently during a high pressure cycle. The phenomenon of such violent bubble implosions is known as cavitation and is characterized by local extreme conditions such as very high temperatures, high cooling rates, high pressure differentials, shock waves and liquid jets. The effects of ultrasonic cavitation promote crystallization and precipitation providing a very homogeneous mixing of the precursors.
The intense mixing and the thereby improved mass transfer improves the seeding of the nuclei. The ultrasonic shockwaves assist the formation of the nuclei.
The more nuclei are seeded, the finer and faster will occur the crystal growth. As ultrasonic cavitation can be very precisely controlled, it is possible to control the crystallization process. Naturally existing barriers for nucleation are easily overcome due to the ultrasonic forces. Sonication assists during so-called secondary nucleation too since the powerful ultrasonic cavitation breaks and deagglomerates larger crystals or agglomerates.
With ultrasound, a pre-treatment of the precursors is normally not necessary since sonication enhances the reaction kinetics. Ultrasonic bubble formation and its violent implosion. Ultrasound enables for the production of crystals tailored to requirements. Three general options of sonication have important effects on the output:. The short application of ultrasound waves to a supersaturated solution can initiate the seeding and formation of nuclei.
As sonication is only applied during the initial stage, the subsequent crystal growth proceeds unimpeded resulting in larger crystals. The continuous irradiation of the supersaturated solution results in small crystals since the unpaused ultrasonication creates a lot of nuclei resulting in the growth of many small crystals.
Pulsed ultrasound means the application of ultrasound in determined intervals. A precisely controlled input of ultrasonic energy allows to influence the crystal growth in order to obtain a tailored crystal size. Sono-crystallization and sono-precipitation processes can be carried out in batches or closed reactors, as continuous inline process or as in-situ reaction. Our broad product range covers your needs.
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