DISTILLATION (Latin. destillatio running off by drops; synonym distillation) — a refining process of liquids from the nonvolatile impurity dissolved in them or division of mixes of liquids into the fractions differing on structure, by evaporation and the subsequent condensation of the formed vapors; it is widely applied in pharmacological and laboratory practice.
Distinguish the simple and fractioned D. Prostaya D. consists in one-time evaporation of liquid with continuous removal of vapors and their subsequent condensation. The turning-out condensate is called distillate, but not sweated part of liquid — a distillation residue. It is not possible to receive pure easily volatile component of simple D. usually. It is only reasonable to apply simple D. when the difference in temperatures of boiling of the liquids which are ratio of mixture is rather big. The fractioned D. consists in repeated repetition of process of evaporation and condensation. Distillates of different structure collect in several receivers (fig. 1). It should be noted that distillate in the receiver I is richer with low-boiling component, in the receiver II the maintenance of this component is lower etc. Each of these distillates (fractions) in turn is subjected again to distillation.
For increase in efficiency of division and reduction of number of distillations use so-called dephlegmators (fig. 2). The essence of action of a dephlegmator consists that steam is condensed in it partially and the distillate which is formed at the same time is returned to the camera of evaporation. Steam which remained in a dephlegmator is enriched with easily volatile component since first of all hardly volatile components are condensed.
In the industry process by the fractioned D. is automated and is carried out in the special devices called by rectification columns (see. Rectification ). Some mixes of liquids are not divided by D. into compound components. Nerazdelnokipyashchy mixes are called azeotropes (see. Constant boiling mixtures ). The liquids forming such mixes it is possible to divide D. into the component which is much in azeotrope and azeotrope.
Apply D. with water vapors to purification of the substances which are not mixing up with water and having high temperatures of boiling at which these substances can decay. Such D. is carried out by a transmission of superheated water vapor through pot liquor.
With water vapor finds broad application in toksikol, researches (see below), in pharmakol. and the perfumery industry for receiving essential oils and fragrant waters.
If the overtaken substance has too high temperature of boiling, apply D. in vacuum, is founded regions on fall of temperature of boiling at reduction of size of pressure over pot liquor.
For cleaning and division of substances with big a pier. it is powerful (weight), decaying even at vacuum distillation, use molecular. In this case distillation is made with a pressure of 10 - 3 — 10 - 4 mm of mercury. and temperature lower, than temperature of boiling of the overtaken substances. The distance from an evaporating surface to a condensing surface shall be less average length of a free run of molecules in these conditions. Surface temperature of condensation shall on 100 ° be lower than surface temperature of evaporation. At molecular D. liquid does not boil, and evaporates from a surface. Therefore for elimination of an overheat of deep layers of liquid the device shall have such design that thickness of a layer of pot liquor was perhaps smaller. So, at distillation of fish oil thickness of a liquid film makes 0,001 — 0,005 mm that corresponds to 400 — 2000 monomolecular layers, and time of its evaporation makes apprx. 0,001 sec. Change of composition of steam in relation to composition of liquid is defined by various evaporation rates of the overtaken components.
At molecular D., unlike other types of D., it is possible to divide mixes of the components having identical temperatures of boiling.
Molecular D. finds broad application during the cleaning and division of thermally unstable organic matters, napr, for release of vitamins from fish oil and vegetable oils.
Distillation at judicial and toxicological researches
is applied by D. with water vapor in a chemical toksikol. the analysis for allocation from biol, objects of various volatile substances: hydrocianic and some carboxylic to - t, alcohols, ethers, aldehydes, ketones, galogenoproizvodny, phenols and phenolic acids, aromatic hydrocarbons, elementorganichesky connections, derivative nitrobenzene and aniline, volatile compounds of phosphorus, alkaloids and other substances.
For the purpose of prevention of losses hydrocianic to - you in the course of such distillation the first fraction of distillate is brought together in the receiver containing solution of strong alkali, and the second and the subsequent fractions — in separate receivers. By D. with water vapor from internals of corpses, biol, liquids, the emetic masses, foodstuff and other material evidences both well water soluble, and almost water-insoluble substances are isolated. It is especially favorable to use this reception at isolation of the substances boiling at high temperature or decaying at the time of boiling. At D. with water vapor flying are also those substances which are dissolved in water in various ratios.
In a judicial toksikol. researches also the fractioned D.
Akvadistillyatora finds application (the ABP; the former name — distillation apparatuses) the installations intended for production of depyrogenized water represent (see. Water depyrogenized ). The principle of a design at various ABP the general: initial water heats up, it is carried to boiling, evaporates, and steam then is condensed and cooled.
In 19 century for D. used tinned distillation stills which were continuously improved. As a result to the middle of 20 century distillation apparatuses of cyclic action and redistillators were replaced with the equipment of continuous action, and their further improvement is carried out on the way of creation of the ABP who are spending smaller amount of heat and initial water, having the effective separating device, the aseptic conditions of collecting, storage and giving supplied with devices for creation on jobs of the received water, elements of automation of processes of receiving, storage and sterilization of depyrogenized water. Modern ABP are the complex installations consisting of vodopodgotovitel, separators, condensers, refrigerators, allonges (transitional tubes to the collection) and collections.
Most of the let-out ABP contains the structural element which is built in the evaporator for heating of water; such ABP are called autonomous. The ABP who do not have the structural element which is built in the evaporator for heating of water are called dependent.
The ABP are might support by several consistently operating evaporators; such ABP are called multistage (special cases of multistage ABP — two-level, three-stage etc.). The greatest distribution in medical practice was gained by one-stage ABP. In most of the ABP devaporation is made with an atmospheric pressure. Such ABP are called atmospheric.
ABP in whom devaporation is carried out in vacuum carry the name of vacuum. In compression ABP devaporation is made with an excessive pressure. In separate steps of multistage ABP devaporation can be made with various pressure. If devaporation in one step of the ABP is carried out with an atmospheric pressure, and in another — in vacuum, then such ABP are called atmospheric and vacuum. In that case when devaporation at different steps is made consistently with an excessive and atmospheric pressure, ABP are called compression and atmospheric.
Because the composition of initial water is various, ABP are supplied with devices for carrying out water treatment — vodopodgotovitel. Magnetic vodopodgotovitel, preparation of water in whom is made under the influence of magnetic field, are put into practice; electrochemical vodopodgotovitel, preparation of water in whom is carried out by means of electric current and various chemical connections, and chemical vodopodgotovitel, processing of water in whom is made by chemical connections.
Heating and evaporation of water in the ABP is made in evaporators. Steam which is formed in evaporators always contains a nek-swarm amount of liquid in the form of drops that leads to pollution of depyrogenized water the substances which are contained in initial water. Are the main reasons for formation of such steam a rupture of bubbles on surfaces of a mirror of evaporation, crushing of liquid and foaming of initial water. At the same time a small amount rather large and a large number of the small drops rising by big height is formed. Fight against large drops is conducted by means of a right choice of height of a vapor space and size of a mirror of evaporation in the evaporator. The small drops which are carried away by steam are removed from it in separators of the ABP.
The ratio, inertial, gravitational and combined separators are put into practice. In ratio separators rotary motion of the separated steam is created and under the influence of accelerations of a particle of moisture are intensively allocated from a flow of steam. Inertial separators have a big contact surface of the purified steam with walls or a nozzle of a separator on which settle drops of water. In gravitational separators of a drop of water drop out of a flow of steam by gravity. In the combined separators two or more principles of separation are used, and separation is usually made in steps.
Steam purified in a separator comes to the structural elements of the ABP intended for condensation and cooling of depyrogenized water. Condensers and refrigerators of various types are put into practice: with the surface of heat exchange formed by walls of the device; submersible lamellar with smooth and ridge walls.
Collecting and storage of depyrogenized water is made in special collections. Usually use collections of two types: with a structural element for heating and cooling of depyrogenized water and without it.
A parametrical number of the ABP used by medical institutions is established. ABP shall have productivity 1 — 1,5; 4; 10; 20 l/hour etc.
A parametrical number of collections — 16, 40, 100 and 250 l is defined.
Bibliography: Bagaturov S.A. Bases of the theory and calculation of distillation and rectification, M., 1974, bibliogr.; Voskresensky P. I. Technology of laboratory works, M., 1973; Heats V. T. and Serafimov L. A. Physical and chemical bases of distillation and rectification, L., 1975, bibliogr.; Kasatkin A. G. Basic processes and devices of chemical technology, M., 1971, bibliogr.; C and and-kov V.B., Shvedovyu.A. and Belova O. I. Ways of preparation of water and their use for receiving a distilled water, the Medical technician, No. 5, page 36, 1971; Shvaykova M. D. Toxicological chemistry, page 65, M., 1975; Sh in e d about in Yu. A. and Bogoudinov R. D. Demineralizator, the Medical equipment, No. 1, page 35, 1969; Shvedovyu.A., Meerkopg.E. and Sokolova A. F. Collections for storage of the distilled or desalinated water, Pharmacy, No. 4, page 60, 1972.
V. A. Popkov; A. F. Rubtsov (court.), Yu A. Shvedov (tekhn.).