Distillation
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distillation (called with alcohol also burning) is a thermal separation process, in order to separate homogeneous mixtures (solutions) of different liquids. Solved solids, for example salts,by crystallization from liquids are separated. One can up-concentrate salt solutions by evaporation. Steam is the desired product, z. B. during seawater desalination steam as drinking or process water, one can speak also of distillation, although this in the strict sense notis correct. Another possibility of separating solutions is the Ausflocken of the materials.
With distillation the basic material is heated up. Developing steam is a mixture from the different components of the solution which can be separated and in a condenser is cooled down. Thatliquid condensate is caught. The word “distillation” is derived from latin word destillare = herabtröpfeln. It was used in the antique one also for other separation processes.
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development
in the antique one above all ethereal oils were distilled. As around the turn of the century (1000 n. Chr.) the sulfur - and nitric acid and above allthe alcohol (ethanol) were discovered, gained distillation substantially significance. In 17. Century were added at important applications fresh water distillation made of sea water and the distillation from pitch and tar to the sealing of the ships .
principles
distillation is a thermal separation process, which has the advantage opposite others that no further materials are usually added such as Adsorbentien or solvents. When used separation aids with distillation energy, those as warmth the systemin the collecting main to be easily supplied and at the condenser again extracted can. Distillation is based on the differently high boiling points of the liquids involved. One says to the fact also that the liquids possess a differently high steam pressure at same temperature. Becomes the systemEnergy supplied, evaporates from the material with the higher steam pressure (lower boiling point) more than from the other material, until itself of the pressure, which stopped temperature and from the material mixture dependent equilibrium. The concentration of the material with the lower boiling point in steamis higher around a completely determined portion than in the output mixture. With a simple distillation maximally this difference is to be obtained.
Since one does not wait in practice, until an equilibrium adjusts itself, but steam takes off and at oneCondenser to strike down leaves, in order to win the distillate, this composition usually is not reached. Additionally the danger exists the fact that the original substance squirts when simmering or foams and is drug along these drops.
repetition of the separation step
throughrepeated distillation of the distillate can be further increased the concentration. The more largely the difference between the boiling points, the less distillation step one needs, in order to achieve a certain concentration.
With the industriellen production this repetition of the distillation steps becomes continuous by rectificationcarried out. One must still differentiate distillation into an a mark process (batch process), as it often emerges in laboratories, in order to isolate for example the pure chemical from a mixture, or kontinuerlicher distillation, those usually in the large distilling columns of a chemistry factory madebecomes.
special one procedure
with distillation many different materials from a mixture is used fractionated distillation. If the boiling points close lie together, nevertheless high purity can be achieved with the rectification by inserting a column. High-boiling materials becomeunder decreased pressure distills, whereby one uses oneself the boiling point degradation too makes.
dragging distillation
with this variant of distillation is added to the material mixture a further substance which can be separated, e.g. Water with the Wasserdampfdestillation. With the production ofethereal oils, which occur in the plant in small concentration (Lavendel, chamomile, and. ) one fills A. into the collecting main (if necessary. cut up) plants and small quantities water, and heat then the collecting main up. The Wasseranteil holds then forsome time the boiling temperature, those if necessary. by work with positive pressure (S.Schnellkochtopf) also over 100 °C to be raised can. The Öldampf goes over head with the water vapour into the radiator and condenses. The water oil mixture can then over decanting separatelybecome. The water vapour carries along thus another, actually insoluble, component. Without employment from water the temperature in the collecting main became possibly. into higher ranges come, within which the oil could be damaged. Distillation is actually only then necessary,if the liquids which can be separated separate into one another, like z. B. the famous alcohol-water solution. Couches actually insoluble mixtures forwards, like z. B. , One can usually separate water oil by setting off and decanting the liquids.
alcohol andother Azeotrope
the probably oldest and one of most well-known applications of distillation is the production of high-per cent alcoholic beverages at the same time (liquor-burn). The concentration of the alcohol leaves itself over the distillative way only by multiple distillation, from an aqueous solutionNormal print, up to maximally 95.58% alcohol increase. Starting from this point are the boiling temperatures of the alcohol-water mixture and the water identically, i.e. they are azeotrop. This is based to dipole moments on the presence of hydrogen bonds, thus. A further increase of the alcohol concentration can only throughthe shift of the azeotropen point take place. This shift can take place by means of pressure change or via the addition of a third material. A multiple distillation is desired can also to the alternative procedure of the rectification be fallen back.
see also
Web on the left of
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