DEFINITION
Water– hydrogen oxide is a binary compound of inorganic nature.
Formula - H 2 O. Molar mass - 18 g / mol. Can exist in three states of aggregation- liquid (water), solid (ice) and gaseous (steam).
Chemical properties of water
Water is the most common solvent. There is an equilibrium in a solution of water, therefore water is called ampholyte:
H 2 O ↔ H + + OH - ↔ H 3 O + + OH -.
Under the influence electric current water breaks down into hydrogen and oxygen:
H 2 O \u003d H 2 + O 2.
At room temperature, water dissolves active metals with the formation of alkalis, while hydrogen is also released:
2H 2 O + 2Na \u003d 2NaOH + H 2.
Water is able to interact with fluorine and interhalogen compounds, and in the second case, the reaction proceeds at low temperatures:
2H 2 O + 2F 2 \u003d 4HF + O 2.
3H 2 O +IF 5 \u003d 5HF + HIO 3.
Salts formed by a weak base and a weak acid undergo hydrolysis when dissolved in water:
Al 2 S 3 + 6H 2 O \u003d 2Al (OH) 3 ↓ + 3H 2 S.
Water is able to dissolve certain substances, metals and non-metals when heated:
4H 2 O + 3Fe \u003d Fe 3 O 4 + 4H 2;
H 2 O + C ↔ CO + H 2.
Water, in the presence of sulfuric acid, enters into reactions of interaction (hydration) with unsaturated hydrocarbons - alkenes with the formation of saturated monohydric alcohols:
CH 2 \u003d CH 2 + H 2 O → CH 3 -CH 2 -OH.
Physical properties of water
Water is a transparent liquid (n.o.s.). The dipole moment is 1.84 D (due to the strong difference in the electronegativity of oxygen and hydrogen). Water has the highest specific heat capacity among all substances in liquid and solid state of aggregation. The specific heat of melting of water is 333.25 kJ/kg (0 C), vaporization is 2250 kJ/kg. Water is capable of dissolving polar substances. Water has a high surface tension and a negative electrical surface potential.
Getting water
Water is obtained by a neutralization reaction, i.e. reactions between acids and alkalis:
H 2 SO 4 + 2KOH \u003d K 2 SO 4 + H 2 O;
HNO 3 + NH 4 OH = NH 4 NO 3 + H 2 O;
2CH 3 COOH + Ba(OH) 2 = (CH 3 COO) 2 Ba + H 2 O.
One of the ways to obtain water is the reduction of metals with hydrogen from their oxides:
CuO + H 2 \u003d Cu + H 2 O.
Examples of problem solving
EXAMPLE 1
| Exercise | How much water should be taken in order to prepare a 5% solution from a 20% solution of acetic acid? |
| Solution | According to the definition of the mass fraction of a substance, a 20% solution of acetic acid is 80 ml of a solvent (water) of 20 g of acid, and a 5% solution of acetic acid is 95 ml of a solvent (water) of 5 g of acid. Let's make a proportion: x = 20 × 95 / 5 = 380. Those. the new solution (5%) contains 380 ml of solvent. It is known that the initial solution contained 80 ml of solvent. Therefore, to get a 5% solution of acetic acid from a 20% solution, you need to add: 380-80 = 300 ml of water. |
| Answer | You need 300 ml of water. |
EXAMPLE 2
| Exercise | During the combustion of organic matter weighing 4.8 g, 3.36 liters of carbon dioxide (N.O.) and 5.4 g of water were formed. The density of organic matter in terms of hydrogen is 16. Determine the formula of organic matter. |
| Solution | Molar masses of carbon dioxide and water calculated using D.I. Mendeleev - 44 and 18 g/mol, respectively. Calculate the amount of substance of the reaction products: n(CO 2) \u003d V (CO 2) / V m; n (H 2 O) \u003d m (H 2 O) / M (H 2 O); n (CO 2) \u003d 3.36 / 22.4 \u003d 0.15 mol; n (H 2 O) \u003d 5.4 / 18 \u003d 0.3 mol. Given that the composition of the CO 2 molecule has one carbon atom, and the composition of the H 2 O molecule has 2 hydrogen atoms, the amount of substance and the mass of these atoms will be equal to: n(C) = 0.15 mol; n(H) = 2×0.3 mol; m(C) = n(C) × M(C) = 0.15 × 12 = 1.8 g; m(H) \u003d n (H) × M (H) \u003d 0.3 × 1 \u003d 0.3 g. Let's determine if there is oxygen in the composition of organic matter: m(O) \u003d m (C x H y O z) - m (C) - m (H) \u003d 4.8 - 0.6 - 1.8 \u003d 2.4 g. The amount of substance of oxygen atoms: n(O) \u003d 2.4 / 16 \u003d 0.15 mol. Then, n(C): n(H): n(O) = 0.15: 0.6: 0.15. Divide by the smallest value, we get n (C): n (H): n (O) \u003d 1: 4: 1. Therefore, the formula of organic matter is CH 4 O. The molar mass of organic matter calculated using the table of chemical elements of D.I. Mendeleev - 32 g/mol. The molar mass of organic matter, calculated using its hydrogen density: M (C x H y O z) \u003d M (H 2) × D (H 2) \u003d 2 × 16 \u003d 32 g / mol. If the formulas of the organic matter derived from the products of combustion and using the density for hydrogen differ, then the ratio of molar masses will be greater than 1. Let's check this: M(C x H y O z) / M(CH 4 O) = 1. Therefore, the formula of organic matter is CH 4 O. |
| Answer | The formula of organic matter is CH 4 O. |
The well-known formula of the basis of life - water. Its molecule consists of two hydrogen atoms and one oxygen, which is written as H2O. If there is twice as much oxygen, then a completely different substance will turn out - H2O2. What is it and how will the resulting substance differ from its “relative” of water?
H2O2 - what is this substance?
Let's dwell on it in more detail. H2O2 is the formula for hydrogen peroxide, yes, the one used to treat scratches, white. Hydrogen peroxide H2O2 - scientific.
A 3% peroxide solution is used for disinfection. In pure or concentrated form, it causes chemical burns to the skin. A thirty percent peroxide solution is otherwise called perhydrol; it was previously used in hairdressing salons to bleach hair. The skin burned by him also becomes white.
Chemical properties of H2O2
Hydrogen peroxide is a colorless liquid with a "metallic" taste. It is a good solvent and is easily soluble in water, ether, alcohols.
Three and six percent peroxide solutions are usually prepared by diluting a thirty percent solution. When concentrated H2O2 is stored, the substance decomposes with the release of oxygen, so it should not be stored in tightly sealed containers in order to avoid an explosion. With a decrease in the concentration of peroxide, its stability increases. Also, to slow down the decomposition of H2O2, various substances can be added to it, for example, phosphoric or salicylic acid. To store solutions of strong concentration (more than 90 percent), sodium pyrophosphate is added to the peroxide, which stabilizes the state of the substance, and aluminum vessels are also used.
H2O2 in chemical reactions can be both an oxidizing agent and a reducing agent. However, more often peroxide exhibits oxidizing properties. Peroxide is considered to be an acid, but a very weak one; salts of hydrogen peroxide are called peroxides.
as a method of obtaining oxygen
The decomposition reaction of H2O2 occurs when a substance is exposed to high temperature (more than 150 degrees Celsius). The result is water and oxygen.
Reaction formula - 2 H2O2 + t -> 2 H2O + O2
The oxidation state of H in H 2 O 2 and H 2 O \u003d +1.
The oxidation state of O: in H 2 O 2 \u003d -1, in H 2 O \u003d -2, in O 2 \u003d 0
2 O -1 - 2e -> O2 0
O -1 + e -> O -2
2 H2O2 = 2 H2O + O2
Decomposition of hydrogen peroxide can also occur at room temperature if a catalyst is used ( Chemical substance speeding up the reaction).
In laboratories, one of the methods for obtaining oxygen, along with the decomposition of berthollet salt or potassium permanganate, is the reaction of peroxide decomposition. In this case, manganese (IV) oxide is used as a catalyst. Other substances that accelerate the decomposition of H2O2 are copper, platinum, sodium hydroxide.
The history of the discovery of peroxide
The first steps towards the discovery of peroxide were made in 1790 by the German Alexander Humboldt, when he discovered the transformation of barium oxide into peroxide when heated. That process was accompanied by the absorption of oxygen from the air. Twelve years later, the scientists Tenard and Gay-Lussac conducted an experiment on the combustion of alkali metals with an excess of oxygen, as a result of which sodium peroxide was obtained. But hydrogen peroxide was obtained later, only in 1818, when Louis Tenard studied the effect of acids on metals; for their stable interaction, a low amount of oxygen was needed. Conducting a confirmatory experiment with barium peroxide and sulfuric acid, the scientist added water, hydrogen chloride and ice to them. After a short time, Tenar found small solidified drops on the walls of the container with barium peroxide. It became clear that it was H2O2. Then they gave the resulting H2O2 the name "oxidized water". This was hydrogen peroxide - a colorless, odorless, hardly evaporable liquid that dissolves other substances well. The result of the interaction of H2O2 and H2O2 is a dissociation reaction, the peroxide is soluble in water.
An interesting fact is that the properties of the new substance were quickly discovered, allowing it to be used in restoration work. Tenard himself, using peroxide, restored the painting by Raphael, which had darkened with time.
Hydrogen peroxide in the 20th century
After a thorough study of the resulting substance, it began to be produced on an industrial scale. At the beginning of the twentieth century, an electrochemical technology for the production of peroxide was introduced, based on the electrolysis process. But the shelf life of the substance obtained by this method was small, about a couple of weeks. Pure peroxide is unstable, and for the most part it was produced in a thirty percent concentration for bleaching fabrics and in three or six percent for domestic use.
Scientists in Nazi Germany used peroxide to create a liquid fuel rocket engine that was used for defense purposes in World War II. As a result of the interaction of H2O2 and methanol / hydrazine, a powerful fuel was obtained, on which the aircraft reached speeds of more than 950 km / h.
Where is H2O2 used now?
- in medicine - for the treatment of wounds;
- in the pulp and paper industry, the bleaching properties of the substance are used;
- in the textile industry, natural and synthetic fabrics, furs, wool are bleached with peroxide;
- as rocket fuel or its oxidizer;
- in chemistry - to obtain oxygen, as a foaming agent for the production porous materials, as a catalyst or hydrogenating agent;
- for the production of disinfectants or cleaning agents, bleaches;
- for bleaching hair (this is an outdated method, since the hair is severely damaged by peroxide);
Hydrogen peroxide can be successfully used to solve various household problems. But only 3% hydrogen peroxide can be used for these purposes. Here are some ways:
- To clean surfaces, pour peroxide into a container with a spray bottle and spray on contaminated areas.
- To disinfect objects, they must be wiped with an undiluted solution of H2O2. This will help cleanse them of harmful microorganisms. Sponges for washing can be soaked in water with peroxide (proportion 1:1).
- To bleach fabrics when washing white things, add a glass of peroxide. You can also rinse white fabrics in water mixed with a glass of H2O2. This method restores whiteness, prevents fabrics from yellowing and helps remove stubborn stains.
- To combat mold and mildew, mix peroxide and water in a spray bottle in a ratio of 1:2. Spray the resulting mixture onto infected surfaces and clean them with a brush or sponge after 10 minutes.
- You can update the darkened grout in the tile by spraying peroxide on the desired areas. After 30 minutes, you need to carefully rub them with a stiff brush.
- To wash dishes, add half a glass of H2O2 to a full basin of water (or a sink with a closed drain). Cups and plates washed in such a solution will shine with cleanliness.
- To clean your toothbrush, you need to dip it in an undiluted 3% peroxide solution. Then rinse under strong running water. This method disinfects the hygiene item well.
- To disinfect purchased vegetables and fruits, spray a solution of 1 part peroxide and 1 part water on them, then rinse them thoroughly with water (can be cold).
- In the suburban area with the help of H2O2, you can fight plant diseases. You need to spray them with a peroxide solution or soak the seeds shortly before planting in 4.5 liters of water mixed with 30 ml of forty percent hydrogen peroxide.
- To revive aquarium fish, if they are poisoned by ammonia, suffocated when aeration is turned off, or for another reason, you can try placing them in water with hydrogen peroxide. It is necessary to mix 3% peroxide with water at the rate of 30 ml per 100 liters and place it in the resulting mixture of lifeless fish for 15-20 minutes. If they do not come to life during this time, then the remedy did not help.
Even as a result of vigorous shaking of a water bottle, a certain amount of peroxide is formed in it, since the water is saturated with oxygen during this action.
Fresh fruits and vegetables also contain H2O2 until they are cooked. When heated, boiled, roasted and other processes with accompanying high temperatures are destroyed a large number of oxygen. That is why cooked foods are considered not so useful, although some amount of vitamins remains in them. Freshly squeezed juices or oxygen cocktails served in sanatoriums are useful for the same reason - due to oxygen saturation, which gives the body new strength and cleanses it.
The dangers of peroxide when ingested
After the above, it may seem that peroxide can be specifically taken orally, and this will benefit the body. But that's not the case at all. In water or juices, the compound is found in minimal amounts and is closely related to other substances. Taking “unnatural” hydrogen peroxide inside (and all peroxide bought in a store or produced as a result of chemical experiments on your own cannot be considered natural in any way, besides, it has too high a concentration compared to natural) can lead to life-threatening and health-threatening consequences. To understand why, you need to turn to chemistry again.
As already mentioned, under certain conditions, hydrogen peroxide breaks down and releases oxygen, which is an active oxidizing agent. can occur when H2O2 collides with peroxidase, an intracellular enzyme. The use of peroxide for disinfection is based on its oxidizing properties. So, when a wound is treated with H2O2, the released oxygen destroys the living pathogenic microorganisms that have entered it. It has the same effect on other living cells. If you treat intact skin with peroxide, and then wipe the area with alcohol, you will feel a burning sensation, which confirms the presence of microscopic damage after peroxide. But with the external use of peroxide at a low concentration, there will be no noticeable harm to the body.
Another thing, if you try to take it inside. That substance, which is capable of damaging even relatively thick skin from the outside, enters the mucous membranes of the digestive tract. That is, chemical mini-burns occur. Of course, the released oxidizing agent - oxygen - can also kill harmful microbes. But the same process will occur with the cells of the alimentary tract. If burns as a result of the action of an oxidizing agent are repeated, then atrophy of the mucous membranes is possible, and this is the first step towards cancer. The death of intestinal cells leads to the inability of the body to absorb nutrients, this explains, for example, weight loss and the disappearance of constipation in some people who practice peroxide "treatment".
Separately, it must be said about such a method of using peroxide as intravenous injections. Even if for some reason they were prescribed by a doctor (this can only be justified in case of blood poisoning, when there are no other suitable drugs available), then under medical supervision and with a strict calculation of dosages, there are still risks. But in such an extreme situation, it will be a chance for recovery. In no case should you prescribe yourself injections of hydrogen peroxide. H2O2 poses a great danger to blood cells - erythrocytes and platelets, as it destroys them when it enters the bloodstream. In addition, a deadly blockage of blood vessels by released oxygen can occur - a gas embolism.
Safety measures in handling H2O2
- Keep out of the reach of children and incapacitated persons. The lack of smell and pronounced taste makes peroxide especially dangerous for them, as large doses can be taken. If the solution is ingested, the consequences of use can be unpredictable. You must immediately consult a doctor.
- Peroxide solutions with a concentration of more than three percent cause burns if it comes into contact with the skin. The burn area should be washed with plenty of water.
- Do not allow the peroxide solution to get into the eyes, as their swelling, redness, irritation, and sometimes pain are formed. First aid before going to the doctor - plentiful rinsing of the eyes with water.
- Store the substance in such a way that it is clear that it is H2O2, that is, in a container with a sticker to avoid accidental misuse.
- Storage conditions that extend its life are a dark, dry, cool place.
- Do not mix hydrogen peroxide with any liquids other than pure water, including chlorinated tap water.
- All of the above applies not only to H2O2, but to all preparations containing it.
O.V. Mosin
Heavy water (deuterium oxide) - has the same chemical formula as ordinary water, but instead of hydrogen atoms it contains two heavy hydrogen isotopes - deuterium atoms. The formula for heavy hydrogen water is usually written as: D2O or 2H2O. Outwardly, heavy water looks like ordinary water - a colorless liquid without taste and smell.
According to its properties, heavy water differs markedly from ordinary water. Reactions with heavy water proceed more slowly than with ordinary water; the dissociation constants of a heavy water molecule are lower than those for ordinary water.
Molecules of heavy hydrogen water were first discovered in natural water by Harold Urey in 1932. And already in 1933, Gilbert Lewis obtained pure heavy hydrogen water by electrolysis of ordinary water.
In natural waters, the ratio between heavy and ordinary water is 1:5500 (assuming that all deuterium is in the form of heavy water D2O, although in fact it is partly in the composition of semi-heavy water HDO).
Heavy water is only slightly toxic chemical reactions in its environment are somewhat slower compared to ordinary water, hydrogen bonds involving deuterium are somewhat stronger than usual. Experiments on mammals have shown that the replacement of 25% of hydrogen in tissues with deuterium leads to sterility, higher concentrations lead to rapid death of the animal. However, some microorganisms are able to live in 70% heavy water (protozoa) and even in pure heavy water (bacteria). A person can drink a glass of heavy water without visible harm to health, all deuterium will be removed from the body in a few days. In this respect, heavy water is less toxic than table salt, for example.
Heavy water accumulates in the remainder of the electrolyte during repeated electrolysis of water. In the open air, heavy water quickly absorbs the vapors of ordinary water, so we can say that it is hygroscopic. The production of heavy water is very energy intensive, so its cost is quite high (approximately $200-250 per kg).
Physical properties of ordinary and heavy water
Physical properties
Molecular mass
Density at 20°C (g/cm3)
t° of crystallization (°C)
boiling temperature (°C)
properties of heavy water
The most important property of heavy water is that it practically does not absorb neutrons, therefore it is used in nuclear reactors for slowing down neutrons and as a coolant. It is also used as an isotope tracer in chemistry and biology. In physics elementary particles heavy water is used to detect neutrinos; for example, the largest solar neutrino detector in Canada contains 1 kiloton of heavy water.
Russian scientists from PNPI have developed original technologies for the production and purification of heavy water on pilot plants. In 1995, the first in Russia and one of the world's first pilot plant was put into operation based on the method of isotope exchange in the water-hydrogen system and water electrolysis (EVIO).
The high efficiency of the EVIO plant makes it possible to obtain heavy water with a deuterium content > 99.995% at. Established technology provides high quality heavy water, including deep purification of heavy water from tritium to residual activity, allowing the use of heavy water in medical and scientific purposes. The facility's capabilities make it possible to fully meet the needs of Russian enterprises and organizations in heavy water and deuterium, as well as to export part of the products. During the work, more than 20 tons of heavy water and tens of kilograms of gaseous deuterium were produced for the needs of Rosatom and other Russian enterprises.
There is also semi-heavy (or deuterium) water, in which only one hydrogen atom is replaced by deuterium. The formula for such water is written as follows: DHO.
The term heavy water is also used in relation to water in which any of the atoms has been replaced by a heavy isotope:
To heavy oxygen water (in it the light oxygen isotope 16O is replaced by heavy isotopes 17O or 18O),
To tritium and superheavy water (containing its radioactive isotope tritium 3H instead of 1H atoms).
If we count all possible different connections with general formula H2O, then the total number of possible "heavy waters" will reach 48. Of these, 39 options are radioactive, and there are only nine stable options: H216O, H217O, H218O, HD16O, HD17O, HD18O, D216O, D217O, D218O. To date, not all variants of heavy water have been obtained in laboratories.
Heavy water plays a significant role in various biological processes.. Russian researchers have long discovered that heavy water inhibits the growth of bacteria, algae, fungi, higher plants, and animal tissue cultures. But water with a deuterium concentration reduced to 50% (the so-called "deuterium-free" water) has antimutagenic properties, increases the biomass and number of seeds, accelerates the development of the genital organs and stimulates spermatogenesis in birds.
Abroad, they tried to give heavy water to mice with malignant tumors. That water turned out to be truly dead: it killed tumors and mice. Various researchers have found that heavy water has a negative effect on plant and living organisms. Experimental dogs, rats and mice were given water, a third of which was replaced with heavy water. After a short time, a metabolic disorder of animals began, the kidneys were destroyed. With an increase in the proportion of heavy water, the animals died. Conversely, a decrease in the content of deuterium by 25% below the norm in the water that was given to animals had a beneficial effect on their development: pigs, rats and mice gave birth to offspring many times more numerous and larger than usual, and the egg production of chickens doubled.
Then the Russian researchers took up the "light" water. Experiments were performed on 3 transplantable tumor models: Lewis lung carcinoma, rapidly growing uterine sarcoma, and slow-growing cervical cancer. "Deuterium-free" water was obtained by researchers using a technology developed at the Institute of Space Biology. The method is based on the electrolysis of distilled water. In the experimental groups, animals with transplanted tumors received water with a reduced content of deuterium, in the control groups - ordinary water. Animals began to drink "lite" and control water on the day of tumor inoculation and received it until last day life.
Deuterium-reduced water delays the appearance of the first nodules at the cervical cancer transplant site. At the time of the occurrence of nodules of other types of tumors, light water does not work. But in all experimental groups, starting from the first day of measurements and almost until the end of the experiment, the volume of tumors was less than in the control group. Unfortunately, although heavy water inhibits the development of all studied tumors, it does not prolong the life of experimental mice.
And then there were voices in favor of the complete removal of deuterium from the water used for food. This would lead to an acceleration of metabolic processes in the human body, and, consequently, to an increase in its physical and intellectual activity. But fears soon arose that the complete removal of deuterium from the water would lead to a reduction in the total duration human life. After all, it is known that our body is almost 70% water. And this water contains 0.015% deuterium. In terms of quantitative content (in atomic percentages), it ranks 12th among the chemical elements that make up the human body. In this regard, it should be classified as a micronutrient. The content of such trace elements as copper, iron, zinc, molybdenum, manganese in our body is tens and hundreds of times less than deuterium. What happens if all the deuterium is removed? Science has yet to answer this question. In the meantime, the undoubted fact is that by changing the quantitative content of deuterium in a plant or animal organism, we can speed up or slow down the course of life processes.
Other names: hydrogen oxide, dihydrogen monoxide.
Water - inorganic compound with the chemical formula H 2 O.
Physical properties
Chemical properties and preparation methods
Water of the highest purity
Distilled water used in laboratories usually still contains appreciable amounts of dissolved carbon dioxide, as well as traces of ammonia, organic bases, and other organic matter. Obtaining very pure water is carried out in several stages. First, 3 g of NaOH (analytical grade) and 0.5 g of KMnO 4 are added to water for every 1 liter, and distillation is carried out in thin section equipment made of Duran 50 or Solidex glass, and only the middle fraction is collected. In this way, dissolved carbon dioxide is removed and organic matter is oxidized. Removal of ammonia is achieved in the second and third distillations with the addition of 3 g of KHSO 4 or 5 ml of 20% H 3 PO 4 , these reagents being preheated with a small amount of KMnO 4 . To prevent the “creeping out” of the added electrolyte into the condensate, a “dry section” is created during the third distillation, for which the length of the tube between the cap on the flask and the condenser is heated to 150 °C. The last distillation, which serves to remove traces of electrolytes, is carried out from a quartz flask with a quartz condenser. The upper tube of the refrigerator, bent at a right angle, is inserted without any sealing material directly into the constriction of the flask (Fig. 1). In order to avoid water splashes, it is advisable to place a spray trap on the steam path. Flasks made of quartz, platinum, Duran 50 or Solidex glass, which are pre-treated with water vapor, serve as receivers. The water obtained in this way is "pure pure" (i.e., with a pH value of 7.00).Rice. 1. Methods for attaching a flask to a refrigerator during the distillation of high purity water.
a - simple (cheap) execution;
b - with a spray trap. The purity of water is determined by measuring its electrical conductivity, which immediately after the distillation of water should be less than 10 -6 Ohm -1 ·cm -1 . The test for the content of carbon dioxide in water is carried out using barite water, and the test for ammonia content is carried out with Nessler's reagent. Very pure water is stored in quartz or platinum vessels. Duran 50 or Solidex glass flasks, previously steamed for a long time and designed exclusively for this purpose, can also be used for this. Such vessels are best closed with polished caps.
Water intended for electrical conductivity measurement
Method 1. Obtaining by distillation. The water of the highest purity required for conducting conductivity measurements is obtained by particularly careful distillation of water that has already been very well purified. The latter should have electrical conductivity at 25°С ( χ ) equal to 1 10 -6 -2 10 -6 Ohm -1 cm -1 . It is obtained by the above method or by double distillation: a) with a mixture of potassium permanganate and sulfuric acid and b) with barium hydroxide. For distillation, a Duran 50 or Solidex glass flask is used with a copper or quartz condenser attached to it.
Rice. 2. The design of the device for distillation of water, designed to measure the electrical conductivity.
1 - heating winding (60 Ohm); 2 - heating mantle (130 Ohm); 3 - adapter on thin sections.
All parts of the apparatus for single-stage distillation according to the Kortyum method (Fig. 2) are made of Duran 50 or Solidex glass, with the exception of a short quartz cooler attached to the distillation apparatus on a normal section. The bent part leading to the refrigerator is heated with a heating element (60 Ohm) to a temperature exceeding 100 ° C, in order to avoid entrainment liquid water into the refrigerator. The 60 cm high reflux condenser located below is equipped with a Widmer coil. The refrigerator is attached to the spare bottle with transitional thin sections. In order for the distillate to retain low electrical conductivity for a long time, transitional sections and a spare bottle must first be treated with hot dilute acid for several days. High purity water χ =(1-2)·10 -6 Ohm -1 ·cm -1) is distilled by passing through the apparatus a slow stream of compressed air from a steel cylinder at a speed of approximately 1 bubble per second. The air is pre-purified by passing it through seven wash bottles, of which one is filled with concentrated sulfuric acid, three contain a 50% potassium hydroxide solution, and three contain "water for measuring electrical conductivity" (the last three wash bottles must be equipped with porous glass plates). The resulting water is taken from the spare bottle by displacing it with purified, as indicated above, compressed air. The water in the flask is heated using a mantle heater with a power of 300 W. The flask can be easily filled with water or emptied with a vertical tube located in the middle of the flask. The easiest way to fill the flask is to stop the flow of air and turn off the heating mantle.
A vessel is connected to the three-way cock at the end of the refrigerator, in which the measurement of the electrical conductivity of the distilled water is carried out until the desired value is reached. χ . After that, the water is sent to the spare collection by switching the tap.
In this way, in 1 hour you can get 100 ml of water, for which at 25 ° C χ=2·10 -7 Ohm -1 cm -1. If the distillation is carried out very slowly, then the electrical conductivity of the resulting water can reach the value χ=10 -8 Ohm -1 ·cm -1 .
Method 2. Obtaining by ion exchange. IN large quantities"Water for measuring electrical conductivity" (x from 7 10 -8 to 1.5 10 -7 Ohm -1 cm -1 can be obtained by ion exchange in the apparatus shown schematically in Fig. 3.
Rice. 3. Installation design for: obtaining high purity water by ion exchange.
1 - ion exchange column;
2 - porous glass filter;
3 - cell for measuring electrical conductivity;
4 - collection;
6 - tube for absorption of carbon dioxide. A Pyrex glass column (75 cm long and 7.5 cm in diameter) with a porous glass plate at the bottom is filled with a mixture (750 g) consisting of one part Amberlite IR 120 (16-50 mesh) and two parts Amberlite IRA 400 (20-50 mesh). 50 mesh). The resin in the column is covered with a perforated polyethylene circle that floats in the solution and serves to prevent the resin from being agitated by the water flow. Normal distilled water is passed through the column. As soon as the electrical conductivity of water, measured in cell 3, reaches a sufficiently low value, it is first washed, and then vessel 4 is filled with it. The ingress of carbon dioxide from air into the water is prevented by two calcium chloride tubes 5 inserted into the column and into the receiver, filled with carbosorb" with an indicator.
Resin pre-treatment and regeneration is carried out as follows. The IR 120 cation exchanger is washed several times with distilled water, removing small particles by decantation. Then, on a glass porous filter, the resin is treated twice alternately with 1 N. NaOH and 2 n. HCl, washing after each treatment with distilled water until neutral. The anion exchanger IRA 400 is also first washed with distilled water. After decantation, the resin on a glass porous filter is treated with 2 N. NaOH, which does not contain carbonates (the water for preparing the solution is freed from carbon dioxide by distillation). Processing is carried out until the concentration of chlorine ions in the eluate is reduced to a minimum. After that, the resin is washed with distilled water until a neutral reaction in the wash water is reached.
The mixture is separated before the resin is regenerated. Resin is added to the beaker, suspended in ethanol, and chloroform is added, with the anion exchanger collecting in the top layer. The mixture is divided into component parts and separate regeneration is carried out.
When ordinary distilled water is passed through the apparatus, it is possible to obtain, without regeneration, at a rate of 1 l/min, 7000 liters of "water for measuring electrical conductivity" with x=5.52 10 -8 Ω -1 cm -1 at 25 °C.
List of used literature
- Volkov, A.I., Zharsky, I.M. Big chemical reference book / A.I. Volkov, I.M. Zharsky. - Mn.: modern school, 2005. - 608 with ISBN 985-6751-04-7.
- M. Bowdler, G. Brouwer, F. Huber, V. Kvasnik, P.V. Schenk, M. Schmeiser, R. Steudel. Guide to inorganic synthesis: In 6 volumes. T.1. Per. With. German / Ed. G. Brouwer. - M.: Mir, 1985. - 320 p., ill. [With. 152-156]
1.000 g/cm3 (3.98shC), tm 0shC, tbp 100shC; when frozen, it forms ice. One of the most common compounds in nature (the amount of water on the Earth's surface is 1.39 × 1018 t, in the atmosphere 1.3 × 1013 t); isotopic varieties are known (see Heavy water). Water is part of many minerals and rocks, all living organisms (45 - 98%, including in the human body about 60% of body weight), is present in the soil. An obligatory component of almost all technological processes in industry and agriculture. Water of special purity is necessary in the production of food products, semiconductors, phosphors, in nuclear technology, chemical analysis and others. Natural waters containing an increased amount of mineral salts, gases, some chemical elements(see Mineralnye Vody).
Modern Encyclopedia. 2000 .
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WATER- water, hydrogen oxide, H2O, the simplest chemical compound of hydrogen and oxygen stable under normal conditions (11.19% H and 88.81% O by mass). Molecular weight 18.0160, freezing t 0°C (at 1 at), boiling t 100ºC (at 1 at), density at ... ... Veterinary Encyclopedic Dictionary
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