Supersaturation is a solution state containing more solute than can be dissolved solvent under normal circumstances. It may also refer to a vapor of a compound having a higher (partial) pressure than the vapor pressure of the compound.
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Special conditions must be met to produce saturated solutions. One of the easiest ways to do this depends on the solubility temperature dependence. As a general rule, the more heat is added to a system, the more soluble a substance. (There are exceptions where the opposite is true). Therefore, at high temperatures, more solutes can dissolve than at room temperature. If this solution is suddenly cooled at a faster rate than the rate of precipitation, the solution becomes saturated until the solute settles to the saturation point determined by the temperature. The precipitation or crystallization of the solute takes longer than the actual cooling time because the molecule needs to meet and form a precipitate without being knocked over by water. Thus, the larger the molecule, the longer it takes to crystallize because of Brown's motion principles.
Saturation conditions should not be achieved through heat manipulation. The ideal gas law
shows that pressure and volume can also be changed to force the system into a state of saturation. If the solvent volume decreases, the solute concentration may be above the saturation point and thus create a saturated solution. The volume drop is most often generated through evaporation. Similarly, increased pressure can push the solution into saturation. These three mechanisms depend on the fact that the condition of the solution can be changed faster than the solute can precipitate or crystallize. Phase_change_ (crystallization_and_condensation) "> Phase change (crystallization and condensation)
Saturated solutions will also crystallize under certain conditions. In normal solution, after the maximum amount of solute dissolved, adding more solute will cause the solute solution to precipitate out and/or solute not soluble at all. Similarly, there are some cases where the solubility of the saturated solution decreases by manipulating the temperature, pressure, or volume but the unsaturated state does not occur. In this case, the solute will only settle. This is because the saturated solution is in a state of higher energy than the saturated solution.
The unsaturated gas solution in a liquid may form a bubble if there is a suitable nucleating site. Supersaturation can be defined as the sum of all partial pressures of gas in liquids that exceed ambient pressure in the liquid.
Crystallization will occur to allow solutions to achieve a lower energy state. (Keep in mind that this process can be exothermic or endothermic). The activation energy comes in the form of crystal nuclei which is added to the aqueous solution (or condensation core when the solution is gas). This nucleus can be added from another source, known as a hatchery, or may form spontaneously in a partial solution due to ionic and molecular interactions. This process is known as primary nucleation. Nuclei must be identical to the crystallized solute. This will allow for dissolved ions to build nuclei and then each other in the process of crystal growth or secondary nucleation. There are many factors that will affect the rate and order of magnitude with which crystallization takes place as well as differences in the formation of crystals and single crystals.
The phase diagram of crystallization shows where undersaturation, saturation, and supersaturation occur at a certain concentration. Concentrations below the solubility curve produce an undersaturation solution. Saturation occurs when concentration is on the solubility curve. If the concentration is above the solubility curve, the solution is considered saturated. There are three mechanisms by which saturation occurs: precipitation, nucleation, and metastability. In the deposition zone, the molecules in the solution are excess and will separate from the solution to form an amorphous aggregate. The excess of aggregate molecules forms a crystal structure while in the nucleation zone. In the metastable zone, the solution takes time to core. To grow crystals while in a metastable zone, conditions will require the formation of a single nucleus while in the nucleation zone, just past the metastable area. The saturated solution can then return to the metastable area.
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Measurement methodology
Table 1. Supersaturation measurement method (Profos, 1987).
History
Supersaturation has been a topic of research throughout history. The initial study of this solution is usually done with sodium sulphate, also known as Glauber Salt, due to the stability of the crystal and the increasing role in the industry. Through the use of this salt, an important scientific discovery was made by Jean-Baptiste Ziz, a botanist from Mayence, in 1809. His experiments enabled him to conclude that the crystallization of saturated solutions came not only from agitation, prior belief) but from the incoming solid matter and acts as an "early" site to form crystals, now called core sites. Expanding on this, Gay-Lussac brings attention to the kinematics of salt ions and the characteristics of the container have an impact on saturation. He is also able to expand the amount of salt by which a saturated solution can be obtained. Then Henri LÃÆ'¶wel came to the conclusion that both the core of the solution and the container wall had a catalyst effect on the solution causing the crystallization. Explaining and providing a model for this phenomenon has become a task taken by newer research. DÃÆ'Ã… © sirà © Ã… © Gernez contributed to this research by discovering that the nuclei must be of the same salt being crystallized to produce crystallisation.
Apps
Supersaturation is a well-known phenomenon found in environmental processes and utilized in commercial manufacturing. For example, honey, a source of nectar food derived from sugar, is a saturated sugar solution. Nectar itself is a sweet solution below the saturation point. After the bees harvest the nectar, they fanned it quickly with their wings to force evaporation. This forces the solution into a state of saturation, creating honey. This explains why honey crystallizes; the solution just goes back to saturated condition.
Certain candies are made by crystallizing a saturated solution. To make candy rocks, manufacturers can raise the solvent to high temperatures, adding sugar to reach high concentrations, and then lower the temperature. If a string or a stick is present in the solution when it cools, the crystallization will occur on the solid and create the candy. This is the same principle that causes maple syrup to crystallize.
Water carbonation also depends on the behavior of saturated solutions. In this case, the solution is saturated with gas. To make soda and water seltzer, carbon dioxide gas is forced to dissolve in water beyond its saturation point. This is done by applying a large amount of pressure to the gas in front of the water followed by sealing the system in an airtight manner.
Saturated properties have practical applications in terms of medicines. By creating a saturated solution of a particular drug, it can be digested in liquid form. Drugs can be made pushed into saturation through a normal mechanism and then prevented from popping out by adding rainfall inhibitors. Drugs in the state are referred to as "supersaturation delivery service delivery," or "SDDS." Oral drug consumption in this form is simple and allows for very precise dose measurements. In particular, it provides a means for drugs with very low solubility to be made into an aqueous solution.
Identification of saturated solutions can be used as a tool for marine ecologists to study the activity of organisms and populations. Photosynthetic organisms release O 2 gas into the water. Thus, the marine area saturated with O 2 gas can certainly be rich with photosynthetic activity. Although some O 2 will naturally be found in the ocean because of its simple physical chemistry, more than 70% of all oxygen gases found in saturated areas can be attributed to photosynthesis activity.
The study of saturation is also relevant to atmospheric studies. Since the 1940s, saturation in the atmosphere has been known. When water is saturated in the troposphere, the formation of the ice lattice is often observed. In a state of saturation, the water particles will not form ice under troposphere conditions. It is not enough for water molecules to form an ice grid at saturation pressure; they need a surface to condense into liquid water or conglomerate water molecules to freeze. For this reason, relative humidity above the ice in the atmosphere can be found above 100%, which means there is saturation. Water supersaturation is actually very common in the upper troposphere, occurring between 20% and 40% of the time. This can be determined using satellite data from Atmospheric Infrared Sounder. Evidence of saturation in the troposphere can be seen in the contrails of aircraft and rocket boats, which need to reach moisture above the saturation of ice to form.
See also
- Supercooling
- Superheating
- Design saturated
- Saturation (chemistry)
References
- "The Web Site of Mr. Lou Chemistry." Factors Affecting Solubility N.p., n.d. Web. Apr. 20th. 2015.
- "Saturated Solution and Solubility." Apchemchys. N.p., n.d. Web. Apr. 20th. 2015.
- "http://www.google.com/patents/CA1320934C?cl=en - Gas Dissolution Method". "Fitzpatrick, Nicholas; John Kuzniarski (August 3, 1993).
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