What is a reverse refrigerator in chemistry. What types of glass refrigerators do you know, and what do they serve? Ball air cooler
From this article it will be known what are chemical refrigerators by the principle of operation, by design, as well as what is used as a coolant.
Chemical refrigerator- This is a laboratory apparatus used to collect condensate during the extraction or isolation of individual fractions of a liquid, and also as one of the elements of installations for the study of various substances.
As a rule, this is a device made of glass. It is a vessel in which condensation occurs, plus a cooling circuit. Air, water or special refrigerants, including solid ones, can act as a coolant.
According to the principle of operation, chemical refrigerators can be:
- straight;
- reverse;
- universal.
Direct refrigerator (another name is descending) used to separate a liquid into low and high boiling components.
Reverse refrigerator used during high-temperature reactions, while the steam is returned to the reactor (glass flask). Of course, boiling could also be carried out in a sealed vessel, but then there is a high probability of a reactor explosion due to high pressure.
The purpose of these two devices is determined by their design difference. A reflux condenser is installed vertically above the flask with boiling liquid so that the vapor after condensation flows down. A straight refrigerator is installed at an angle so that the liquid from it can freely drain into the receiver.
Universal devices have a design that allows them to be used as direct and reverse refrigerators.
Types of refrigerators depending on the types of condenser vessels
In total, according to the design features, four types of chemical coolers are distinguished. Consider the features of each of them.
Liebig refrigerator
Other names for this downward cooling device are once-through cooler or straight tube cooler (SRT). It was invented by the German chemist Justus von Liebig. The design of the apparatus consists of two glass tubes sealed one inside the other. The inner tube is filled with vapors of a boiling liquid, and running water circulates inside the outer tube.
This design has a wide range of applications and can be part of a device that performs simple or vacuum distillation.
Refrigerator Allina
Another name - "ball" device received from the shape of the inner tube, reminiscent of series-connected balls. This design allows you to increase the heat exchange area and increase productivity. But since, with its inclined installation, condensate can accumulate in the balls, the Allin refrigerator can only work as a reverse one.
coil refrigerator
Lauren R. Graham changed the design of a simple chemical refrigerator in a different way by placing a glass coil inside the tube. Condensation in it occurs much faster than in a direct-flow or ball, but the device can only be used as a descending one due to the capillary effect.
A variation of the spiral refrigerator is the Städeler cooling device. Here, ice with common salt or solid carbon dioxide with acetone is used as a coolant. It is used for liquids with a low boiling point.
Dephlegmator Dimrota
It is similar in design to a spiral (coil) refrigerator, but has a slightly different principle of operation of the Dimroth dephlegmator.
This refrigerator is a flask, inside of which there is a spiral cooled by water. The coils of the helix can be extended or tightly wound depending on the application. Liquid vapors condense on spirals and are discharged through an opening at the bottom of the flask. The temperature is easily adjusted thanks to the thermometer fitting located at the top of the flask.
finger-shaped refrigerator
This apparatus is also called a "cooling finger" or immersion cooler. It has a number of advantages: compact dimensions, no need to specifically fix it in the cooling system
Air and water coolers
Depending on the cooler used, cooling devices are divided into air and water.
The air cooler can be used in the chemical industry for the synthesis of rubber, alcohol, oil distillation in areas with limited water resources or to reduce the cost of cleaning, pumping and softening water. Such devices are easy to maintain, do not require large repair and maintenance costs, and also have a longer service life compared to water coolers.
If the condensation reaction occurs at temperatures above 150°C, water cooling will cause the glass to crack due to the sudden temperature change. In this case, an air cooler is used. By design, it can be direct-flow or ball.
The water apparatus for cooling uses running water as a refrigerant. It is used not only in laboratory experiments, but also in industry or medicine, for example, to obtain distilled water. They are made in any of the designs listed above.
Important: regardless of the design of the refrigerator, water or other required refrigerant is supplied to the condenser from the bottom up so that the shirt is completely filled and the operation of the device is efficient.
Conclusion
Chemistry has found wide application in the daily life of modern man. Not only modern housewives use the reaction of the interaction of soda and acid to give splendor to pastries, but laboratory equipment has also found its use. For example, chemical refrigerators are used by those who prefer homemade alcohol to store-bought.
Video: What is a direct and reverse refrigerator | USE Chemistry | Leah Mendeleeva
Video: Refrigerator Overview
Refrigerators- serve to condense vapors of boiling liquid in distillation apparatuses. Depending on the operating conditions, the liquid is processed in the refrigerator when the vapors (condensate) are cooled and must either be discharged to the receiver or returned to the vessel in which the heating is carried out. This difference in the purpose of refrigerators determines their shape and name. Refrigerators designed to collect condensate are called direct or descending, and refrigerators from which condensate is returned to the process are called reverse.
Direct refrigerators (Liebig). Liebig refrigerators are very common in laboratories, consisting of a long glass tube (forshtos), one end of which is widened. This tube is passed through a glass or metal jacket or sleeve, and secured with pieces of a rubber tube fitted onto the ends of the sleeve. Sometimes Liebig refrigerators are found, in which the refrigeration tube is soldered to the shirt.
At the ends of the coupling (perpendicular to its axis) there is one outlet. Rubber tubes are put on them, one of which, located near the narrow end, is connected to a water tap, and the other is taken into the sewer. With this connection of the tubes, the water in the refrigerator moves towards the vapors of the cooled liquid. When connecting the refrigerator, the following rules must be observed: water must always enter the refrigerator from the lower lowered end and exit from the upper raised end. The cooling jacket (coupling) must always be filled with water. Otherwise, during prolonged distillation, the refrigeration tube becomes very hot and may burst at the border with the water level.
With prolonged use, a reddish-yellow coating of iron oxides often forms in the refrigeration jacket, which enters with water from water pipes. Plaque makes it difficult to see the refrigeration tube and must be removed periodically. To do this, the refrigerator is disconnected from the water tap, all the water is released and 10-16% hydrochloric acid is poured into the refrigeration jacket, while clamps are put on the rubber tubes near the outlets. By carefully turning the refrigerator, the iron oxide plaque is dissolved in hydrochloric acid, then the acid is poured out, the refrigerator is again connected to the water supply and the water is driven off for 5-6 minutes. It is possible to distill a liquid using a Liebig refrigerator only when the temperature of its vapor does not exceed 150 ° C.
Reverse refrigerators can be ball (Allin refrigerators), coil and other forms. In ball coolers, the tube consists of spherical extensions, while in coil coolers it is folded in the form of a spiral. This form of tubes increases the cooling surface and more complete condensation of the vapor occurs.
The Allina refrigerator is installed only in a vertical position, but not inclined, since in the latter case condensed liquid will collect in the balls, interfering with the correct selection of fractions.
Soxhlet ball cooler most often used as a reverse. Cooling water enters through a small outlet into the internal spherical cavity and flows out of the right process. Liquid vapors pass between the inner surface and the outer wall. Thus, the vapors are cooled immediately from both surfaces; with external - air, and with internal - cold water.
There are a number of special refrigerators, for example, refrigerators in which the refrigeration tube has the form of a spiral (Fig. 14, position 6). This is done in order to increase the cooling surface without increasing the size of the refrigerator.
Refrigerators Domrat are universal, as they can be used as a downward and reverse. The refrigerator can withstand significant temperature fluctuations. Its advantage is that water vapor from the environment does not condense on its outer walls.
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The ball cooler ХШ is designed for heat exchange of two streams, cooling and condensation of liquid vapors. It is used exclusively as a reverse, as it has spherical extensions inside the outer flask. When condensing, the vapors in the refrigerator become turbulent. This type of refrigerator has higher cooling properties, significantly exceeding those of Liebig-type refrigerators.
Features of use
The supply of the cooling agent is carried out from the bottom up. The ball device allows you to insert the stirrer axis into it, as well as introduce various substances into the reactor. Usually the number of balls ranges from 2 to 8.
When used, the ball cooler is installed in an inclined position. This avoids flooding, while the slope should not be significant, otherwise the condensate will not have time to drain back into the flask. The accumulation of condensate affects the cooling efficiency.
In our online store you can buy the following types of ball refrigerators:
- length from 20 to 40 cm;
- number of balls - 2, 6, 8;
- connection input / output - 14/23, 29/32, 45/40 and without shlif.
Benefits of a ball cooler
- The special ball design gives the refrigerator an impressive heat exchange surface.
- Low vapor resistance allows you to get more high-strength moonshine.
You can buy a reverse refrigerator on this page.
You took beer with you on a hike, but there was not a stream with icy water along the route, and the cold ended. How to quickly cool beer or other drinks, and at the same time not by a couple of degrees, as it is done due to evaporation, but in such a way as to really cool the drink and enjoy the heat? To do this, you need to take an extremely compact chemical refrigerator with you, which you can prepare in advance and always have the right charge on hand to cool food, freeze bruises and other needs.
Cold will help with: bruises, sprains, fractures, dislocations, swelling, burns, insect bites, heat stroke, inflammation, the need to stop bleeding (from the nose), the need to cool food.
Method for obtaining chemical cold
To prepare it, you need water and ammonium nitrate - a common fertilizer. You can easily find it in a flower shop, its price is low, so your urgent refrigerator will be cost-effective.
The mass proportion of water and saltpeter is 60% to 40%, by volume it turns out 1:1. Stir this mixture in a bottle. When dissolved in water, saltpeter absorbs a large amount of heat. If salt, when dissolved, lowers the temperature by 3 degrees, then the same amount of saltpeter by 23 degrees! The refrigerator is chemically ready for use. If you freeze a half-filled bottle with water, and then fill it with saltpeter (it is not necessary to grind), then we get a long-lasting source of cold.
Another great idea. On a hike, you can make a refrigerator from a tourist rug and a bottle of mixture. At the right time, we put the mixture into action and wrap it in a rug, and close the open ends with a rag or spare clothes.
The used mixture, before pouring it, must be heavily diluted with water if you do not want to harm the plants.
About a thermos, how to make it from a bottle.
Experience with cold created by chemical means
Mix 100 g of snow or ice with 33 g of rock salt - the temperature of the resulting mixture will drop to -20 ° C. If you mix 100 g of snow or ice with 100 g of potassium nitrate, the temperature of the mixture will drop to -30 ° C. The temperature of the cooling mixture, consisting of 100 g of snow (or ice) and 150 g of potassium chloride hydrate reaches -45 ° C. And what about in summer, when there is no snow and ice? In the warm season, you can use such chemical compounds that, when dissolved in water, absorb heat, thereby helping to reduce the water temperature to -35 ° C. Of course, the water must be cold, and the following compounds must be taken in the following proportion (by weight ) in relation to water:
ammonium chloride 3
sodium nitrate 5
ammonium nitrate 10
sodium sulfide + hydrochloric acid 40
ammonium thiocyanate or potassium 15
In order to avoid large losses of cold, it is advisable to prepare the solution in a thermos.
When finished, pour the solution into a cup and remove water from it by evaporating. The substance remaining after evaporation can be reused for experiments.
Fridge- a device for condensing steam using a cooling medium, most often water.
Depending on the method of application, the following types of refrigerators are distinguished:
- direct refrigerator (descending) - used to condense vapors and remove the resulting condensate from the reaction system. The condensate is collected in a receiver flask.
- Reverse refrigerator - it is used to condense vapors and return condensate to the reaction mass. Such refrigerators are usually installed vertically.
Figure 1. shows various constructive types of refrigerators.
Fig.1 Constructive types of refrigerators
a air cooler
b-ball air cooler
Liebig's refrigerator
g-ball cooler
d-coil refrigerator
e-Städeler refrigerator
refrigerator Dimrota
s-refrigerator combining the principles of Liebig and Dimroth refrigerators
and - "cooling finger"
air cooler(fig.1-a)
It belongs to the simplest refrigerators in design and is a long glass tube. Such a refrigerator is used only when working with high-boiling liquids (boiling point> 150 ° C), since the cooling effect of air is small. Refrigerator can be used as direct or reverse. As an inverse refrigerator, this type of refrigerator is inefficient: the movement of the liquid mainly corresponds to the laminar flow and the substance is easily "ejected". Such a cooler can be used as a downcomer if the distillation rate is not too high for substances with a boiling point >150°C.
Ball air cooler(Fig.1-b)
Used in reverse. Ball coolers are more efficient than conventional (straight in design) air coolers due to the larger heat transfer surface. Such refrigerators have found application for semi-microsynthesis, where the amount of heat removed is small and air cooling is quite sufficient for the condensation of even low-boiling substances. (If necessary, in this case, the refrigerator can be wrapped with damp filter paper.)
Liebig refrigerator(fig.1-c)
It is mainly used as a descender up to about 160°C. Refrigerant for substances with a boiling point The Liebig refrigerator consists of two glass tubes sealed one inside the other. Liquid vapor moves through the inner tube, and a cooling agent (cold water) moves through the outer tube (shirt).
As a converse, such a refrigerator is ineffective, since it has a small cooling surface and a laminar vapor flow; for this purpose, it is used only for relatively high-boiling (bp > 100°C) compounds. Atmospheric moisture condenses on the outer surface of the cooler, which can get inside the flask through capillary leaks in the thin section, so the thin sections on the cooler and the flask should be thoroughly lubricated. It is also recommended to put on a cuff made of dry filter paper on the refrigerator above the section. Higher boiling liquids at the junction A (Fig. 1-c) can cause the occurrence of internal stress, which causes glass cracking. Therefore, Liebig refrigerators cannot be made from non-heat-resistant glass.
Figure 2 shows an example of using a Liebig refrigerator for simple distillation.
Fig. 2 Installation for a simple distillation.
1-Wurtz flask
2 Liebig refrigerator
3-alonge
4-flask-receiver
ball cooler(Fig.1-d)
It is used exclusively as a reverse. Since this cooler has spherical expansions, the vapor flow in it becomes turbulent; the cooling effect of such a refrigerator is much higher than that of the Liebig refrigerator. 
However, atmospheric moisture also condenses on its outer surface and the junction A is also dangerous. The coolant is supplied from bottom to top. It is convenient to insert the stirrer shaft through a ball cooler, to introduce various substances into the reactor, which are well washed into the flask by condensate and heated by it. Typically, the number of balls in such refrigerators ranges from 3 to 8. To avoid flooding, when the condensate does not have time to drain back into the flask with boiling liquid, the reverse ball cooler is installed in an inclined position, but the slope should not be too large so that condensate does not accumulate in the balls . The accumulation of condensate leads to a decrease in the effective cooling surface of the refrigerator.
coil refrigerator(Fig. 1-e)
Never used as a return, as condensate that does not drain well enough along the folds of the coil can be thrown out of the refrigerator and cause an accident. The vertically mounted coil cooler is the most efficient downcomer cooler, especially for low boiling materials.
Refrigerator Städeler(fig.1-e)
Modification of a serpentine refrigerator, in which the cooling vessel can be filled with a mixture of ice and sodium chloride, solid carbon dioxide with acetone, etc. Such a refrigerator can be used to condense substances boiling at very low temperatures.
Refrigerator Dimrota(Fig. 1-g) A very efficient reflux condenser. It is also used as a downcomer if the relatively large distillate losses on the coil can be neglected. The junction of the coil with jacket A is outside the zone with a large temperature difference, therefore, using such a refrigerator when working with liquids boiling above 160 ° C, you can not be afraid of complications. Since the outer jacket of the refrigerator is air at room temperature, atmospheric moisture does not condense on its surface (see above). True, low-boiling substances can "creep" along the inside of the shirt and thereby "drag" the cooling zone. The Dimroth refrigerator is therefore not suitable as a reverse for relatively low-boiling substances, such as ether. At the upper open end of the refrigerator, atmospheric moisture easily condenses on the water supply hoses, so it is provided with a calcium chloride tube.
Immersion cooler - "cooling finger"(fig.1-i)
This specially shaped reflux condenser (it does not need to be specially fixed in the cooling system) is used primarily in devices for semi-micro methods. If a “cooling finger” is introduced into the reaction vessel on the stopper, the instrument must not be sealed.
General note: it is necessary to constantly monitor that the circulation of water through the jacket of the refrigerator does not stop, since turning off the refrigerator can lead to fires and explosions!
