Do not forget that old highschool chemistry experiment where salt crystals precipitate out of a saltwater solution — or perhaps the one where rock candy crystals form from sugar water? It seems that your understanding of how crystals formed in those solutions is likely to be mistaken.
A brand new theory “demystifies” the crystallization process and shows that the fabric that crystallizes is the dominant component inside an answer — which is the solvent, not the solute. The speculation could have implications for all the things from drug development to understanding climate change.
“Crystals are ubiquitous — we use them in all the things from technology to medicine — but our actual understanding of the crystallization process has been lacking,” says James Martin, professor of chemistry at North Carolina State University and creator of a paper in Matter that outlines the idea.
“The prevailing ideas around dissolving and precipitating are that they are essentially the reverse of one another, but they don’t seem to be. In point of fact, they’re completely different processes,” Martin says.
“Using the highschool chemistry experiment with getting precipitate out of an answer for example: after I dissolve salt (the solute) into water (the solvent), the water is dominant. It dissolves the salt by essentially ripping it apart,” Martin says. “If I then need to grow a salt crystal from that solution, the dominant phase must turn out to be the salt — which is the solvent at that time and is the one which forms the crystal.”
Thermodynamic phase diagrams, which describe concentration and temperature-dependent transition points in solutions, may be used for example the brand new theory, dubbed the transition-zone theory.
The speculation demonstrates that crystallization happens in two steps: first a melt-like pre-growth intermediate forms. Then that intermediate can organize into the crystal structure.
“To grow a crystal out of an answer, you’ve gotten to quickly separate the solvent and solute,” Martin says. “After we check with the ‘melt’ here, we’re talking in regards to the pure phase of the solvent prior to crystal formation. The difference here is that my theory shows you recuperate, faster crystal growth by moving your solution toward conditions that emphasize the solvent; in other words, the solvent — not the impurity inside it — controls the speed of crystal growth.”
Martin applied his theory to quite a few different solutions, concentrations and temperature conditions and located that it accurately describes the speed and size of crystal formation.
“The foremost issue with previous descriptions of crystallization was the perception that crystals grow by having independent solute particles diffuse to, after which attach to a growing crystal interface,” Martin says. “As a substitute, it’s essential to know cooperative ensembles of the solvent to explain crystal growth.”
In accordance with Martin, the necessary aspect of the brand new theory is its concentrate on understanding how solute impurities disrupt that cooperative ensemble of solvent.
“By understanding the interplay of temperature and concentration, we will predict exactly how briskly and huge crystals will grow out of solution.”
Martin believes the phase diagrams could have necessary applications for not only crystal formation, but for stopping crystal formation, akin to stopping kidney stones from growing.
“Crystals underpin technology — they’re throughout us and impact our each day lives,” Martin says. “This theory gives researchers easy tools to know the ‘magic’ of crystal growth and make higher predictions. It’s an example of how foundational science lays foundation for solving every kind of real-world problems.”
The paper appears in Matter and was supported partly by the National Science Foundation.