Distilled and demineralized water. Determination of quality indicators of distilled water
Information about the impact of demineralized water on the state of the body is based on experimental data and observations. Experiments were carried out on laboratory animals and human volunteers, observations were made on large groups people who consume demineralized water, and individuals ordering water treated with reverse osmosis and children for whom baby food was prepared with distilled water. Since the information available over the period of these studies is limited, we must also take into account the results of epidemiological studies comparing the health effects of low-mineralized (softer) and highly mineralized water. Demineralized water that has not been subsequently enriched with minerals is an extreme case. It contains solutes such as calcium and magnesium, which are the major contributors to hardness, in very small amounts.
The possible consequences of drinking mineral-poor water fall into the following categories:
- effects on the intestinal mucosa, mineral metabolism and homeostasis, and other bodily functions;
- low intake / lack of intake of calcium and magnesium;
- low intake of other macro- and microelements;
- loss of calcium, magnesium and other macronutrients during cooking;
- possible increase in the intake of toxic metals into the body.
Effects on the intestinal mucosa, mineral metabolism and homeostasis, and other bodily functions
Distilled and low-mineralized water (total mineralization
Williams (4) showed in his report that distilled water can cause pathological changes in epithelial cells in the intestines of rats, possibly due to osmotic shock. However, Schumann (5), who later conducted a 14-day experiment with rats, did not get such results. Histological studies did not reveal any signs of erosion, ulceration, or inflammation of the esophagus, stomach, and small intestine. Changes in the secretory function of animals (increased secretion and acidity of gastric juice) and changes in muscle tone stomach; these data are given in the WHO report (3), but the available data do not allow unequivocally to prove the direct negative effect of water with low salinity on the mucosa of the gastrointestinal tract.
To date, it has been proven that the consumption of water, poor in minerals, has a negative impact on the mechanisms of homeostasis, the metabolism of minerals and water in the body: increased fluid excretion (diuresis). This is due to the washing out of intra- and extracellular ions from biological fluids, their negative balance. In addition, the total water content in the body and the functional activity of some hormones that are closely related to the regulation of water metabolism change. Experiments on animals (mainly rats), which lasted about a year, helped to establish that the use of distilled water, or water with a total mineralization of up to 75 mg / l, leads to:
- an increase in water consumption, diuresis, extracellular fluid volume, serum sodium and chloride ion concentrations and their increased excretion from the body; resulting in an overall negative balance,
- the number of red blood cells decreases, hematocrit index;
- A group of scientists led by Rakhmanin, studying the possible mutagenic and gonadotoxic effects of distilled water, found that distilled water does not have such an effect.
However, there was a decrease in the synthesis of the hormones triiodothyranine and aldosterone, increased secretion of cortisol, morphological changes in the kidneys, including severe atrophy of the glomeruli and swelling of the layer of cells lining the vessels from the inside, preventing blood flow. Insufficient ossification of the skeleton was found in the embryos of rats whose parents consumed distilled water (1-year experiment). It is obvious that the lack of mineral substances was not replenished in the body of rats even at the expense of nutrition, when the animals received their standard diet with the necessary energy value, nutrients and salt composition.
The results of an experiment conducted by WHO scientists on human volunteers showed a similar picture (3), which made it possible to outline the main mechanism of the effect of water with a mineralization of up to 100 mg/l on the exchange of water and minerals:
1) increased diuresis (by 20% compared with the norm), the level of fluid in the body, the concentration of sodium in the serum; 2) reduced serum potassium concentration; 3) increased excretion of sodium, potassium, chloride, calcium and magnesium ions from the body.
Presumably, water with low salinity affects the osmotic receptors of the gastrointestinal tract, causing an increased release of sodium ions into the intestine and a slight decrease in osmotic pressure in the portal venous system, followed by an active release of sodium ions into the blood as a response. Such osmotic changes in the blood plasma lead to a redistribution of fluid in the body. The total volume of extracellular fluid increases, water moves from erythrocytes and tissue fluid into the plasma, as well as its distribution between intracellular and tissue fluids. Due to changes in the volume of plasma in the bloodstream, receptors that are sensitive to volume and pressure are activated. They prevent the release of aldosterone and, as a result, the release of sodium increases. The reaction of volume receptors in the vessels can lead to a decrease in the release of antidiuretic hormone and increased diuresis. The German Nutrition Society came to similar conclusions and recommended against drinking distilled water (7). The message was published in a response to the German publication The Shocking Truth About Water (8), whose authors recommended drinking distilled water instead of ordinary drinking water. Society in its report (7) explains that liquids human body always contain electrolytes (potassium and sodium), the concentration of which is under the control of the body itself. The absorption of water by the intestinal epithelium occurs with the participation of sodium ions. If a person drinks distilled water, the intestines are forced to "add" sodium ions to this water, removing them from the body. The fluid is never excreted from the body in the form pure water, in parallel, a person also loses electrolytes, which is why it is necessary to replenish their supply from food and water.
Improper distribution of fluid in the body can even affect the functions of vital organs. The first signals are fatigue, weakness and headache; more serious - muscle cramps and heart rhythm disturbances.
Additional information was collected during experiments with animals, clinical observations in some countries. Animals fed water enriched with zinc and magnesium had a much higher concentration of these elements in the blood serum than those fed enriched feed and drinking low-mineralized water. An interesting fact is that during enrichment, significantly more zinc and magnesium were added to the feed than to the water. Based on experimental results and clinical observations of mineral-deficient patients receiving intravenous distilled water nutrition, Robbins and Sly (9) hypothesized that the consumption of low-mineralized water was the cause of increased mineral excretion from the body.
The constant use of low-mineralized water can cause the changes described above, however, symptoms may not appear, or they may appear many years later. However, serious damage, for example, the so-called. water intoxication or delirium, may be due to intense physical work and drinking some distilled water (10). The so-called water intoxication (hyponatremic shock) can occur not only as a result of the consumption of distilled water, but also drinking water in general. The risk of such "intoxication" increases with a decrease in water salinity. Serious health problems arose among climbers who ate food cooked on melted ice. Such water does not contain anions and cations necessary for a person. Diseases such as cerebral edema, convulsions, and acidosis have occurred in children who consumed drinks prepared with distilled or low-mineralized water (11).
Low intake / no intake of calcium and magnesium
Calcium and magnesium are very important for humans. Calcium is an important component of bones and teeth. It is a regulator of neuromuscular excitability, participates in the work of the conduction system of the heart, contraction of the heart and muscles, transmission of information within the cell. Calcium is an element responsible for blood clotting. Magnesium is a cofactor and activator of over 300 enzymatic reactions including glycolysis, ATP synthesis, transport of minerals such as sodium, potassium and calcium across membranes, protein synthesis and nucleic acids, neuromuscular excitability and muscle contractions.
If we evaluate the percentage contribution of drinking water to the total intake of calcium and magnesium, it becomes clear that water is not their main source. However, the importance of this source of minerals cannot be overestimated. Even in developed countries, food products cannot compensate for the deficiency of calcium and, especially, magnesium, if drinking water is poor in these elements.
Epidemiological studies carried out in different countries over the past 50 years have shown that there is an association between increased cardiovascular disease and subsequent death and soft water consumption. When comparing soft water with hard and rich in magnesium, the pattern can be traced very clearly. The review of research is accompanied by recently published articles (12-15), the results are summed up in other chapters of this monograph (Calderón and Crown, Monarca). Latest Research have shown that consumption of soft water, for example, poor in calcium, can lead to an increased risk of fractures in children (16), neurodegenerative changes (17), premature birth and reduced birth weight (18) and some types of cancer (19,20). In addition to an increased risk of sudden death (21–23), drinking magnesium-poor water has been associated with heart failure (24), late pregnancy toxemia (so-called preeclampsia) (25), and some types of cancer (26–29). ).
Specific information about changes in calcium metabolism in people forced to drink demineralized water (for example, distilled, filtered through limestone) with low calcium content and mineralization was obtained in the Soviet city of Shevchenko (3, 30, 31). In the local population, decreased activity of alkaline phosphatase and concentrations of calcium and phosphorus in plasma and pronounced decalcification of bone tissue were observed. Changes were most pronounced in women (especially pregnant women) and depended on the length of stay in the city of Shevchenko. The importance of sufficient calcium in the water was established in the above experiment with rats fed a complete diet rich in nutrients and salts and demineralized water artificially enriched with minerals (400 mg/l) and calcium (5 mg/l, 25 mg/l, 50 mg/l)
(3, 32). In animals that drank water containing 5 mg/l of calcium, a decrease in thyroid function and a number of other body functions was noted compared to animals in which the dose of calcium was doubled.
Sometimes the consequences of insufficient intake of certain substances in the body are visible only after many years, but the cardiovascular system, which lacks calcium and magnesium, reacts much faster. A few months of drinking water deficient in calcium and/or magnesium is sufficient (33). Case in point- the population of the Czech Republic and Slovakia in 2000-2002, when the reverse osmosis method was used in the centralized water supply system.
Over the course of weeks or months, there have been many complaints related to severe magnesium (and possibly calcium) deficiency (34).
The complaints of the population related to cardiovascular disease, fatigue, weakness, muscle cramps and actually coincided with the symptoms listed in the report of the German Nutrition Society (7).
Small intake of other macro- and microelements
Despite the fact that drinking water, with rare exceptions, is not a significant source of important elements, its contribution is for some reason very important. Modern technologies food preparation does not allow most people to get enough minerals and trace elements. In the event of an acute deficiency of any element, even a relatively small amount of it in water can play a significant protective role. Substances in water are dissolved and are in the form of ions, which makes it much easier for them to be adsorbed in the human body than from food, where they are bound into various compounds.
Animal experiments have also shown the importance of the presence of trace amounts of certain substances in water. For example, Kondratyuk (35) showed in a report that the difference in the intake of trace elements led to a sixfold difference in their concentrations in the muscle tissue of animals. The experiment was carried out for 6 months; rats were divided into 4 groups and used different water: a) tap water; b) slightly mineralized; c) slightly mineralized, enriched with iodine, cobalt, copper, manganese, molybdenum, zinc and fluorine in normal concentrations; d) slightly mineralized, enriched with the same elements, but in 10-fold greater quantities. In addition, unenriched demineralized water has been found to have a negative effect on hematopoietic processes. In animals that received water that was not enriched with trace elements with low mineralization, the number of red blood cells was 19% lower than in individuals that received ordinary tap water. The difference in hemoglobin content was even greater when compared to animals fed enriched water.
Recent studies of the environmental situation in Russia have shown that the population that consumes water with a low content of minerals is at risk of many diseases. These are hypertension (high blood pressure) and changes in the coronary vessels, gastric and duodenal ulcers, chronic gastritis, goiter, complications in pregnant women, newborns and infants such as jaundice, anemia, fractures and growth problems (36). However, it is not entirely clear whether all these diseases are associated with a lack of calcium, magnesium and other important elements, or with other factors.
Lutai (37) has carried out numerous studies in the Ust-Ilim region of Russia.
The object of research were 7658 adults, 562 children and 1582 pregnant women and their newborns; studied morbidity and physical development. All these people are divided into 2 groups: they live in 2 areas where the water has different mineralization. In the first of the selected areas, water is characterized by a lower mineralization of 134 mg/l, calcium and magnesium content - 18.7 and 4.9, respectively, bicarbonate ion - 86.4 mg/l. In the second region - more highly mineralized water 385 mg/l, calcium and magnesium content - 29.5 and 8.3, respectively, bicarbonate ion - 243.7 mg/l. The content of sulfates, chlorides, sodium, potassium, copper, zinc, manganese and molybdenum was also determined in water samples from two regions. The food culture, air quality, social conditions and time of residence in the region were the same for the residents of the two districts. Residents of an area with lower water salinity were more likely to suffer from goiter, hypertension, coronary heart disease, stomach and duodenal ulcers, chronic gastritis, cholecystitis, and nephritis. Children developed more slowly and suffered from some growth abnormalities, pregnant women suffered from edema and anemia, and newborns were more often ill.
A lower incidence rate was noted where the calcium content in the water was 30-90 mg/l, magnesium - 17-35 mg/l, and the total mineralization - about 400 mg/l (for water containing bicarbonates). The author came to the conclusion that such water is close to the physiological norm for humans.
Losses of calcium, magnesium and other macronutrients during cooking
It became known that in the process of cooking on soft water, important elements are lost from products (vegetables, meat, cereals). Losses of calcium and magnesium can reach 60%, other trace elements - even more (copper-66%, manganese-70%, cobalt-86%). In contrast, during hard water cooking, mineral loss is markedly lower, and the calcium content of the finished meal may even increase (38-41).
Although most nutrients come from food, cooking with brackish water can significantly reduce the overall intake of some elements. Moreover, this shortage is much more serious than when using such water only for drinking purposes. The modern diet of most people is not able to meet the body's needs for all the necessary substances and, therefore, any factor that contributes to the loss of minerals during cooking can play a negative role.
Possible increase in the intake of toxic metals into the body
The increased risk of toxic metal intake may be the result of two reasons: 1) more intensive release of metals from materials in contact with water, leading to an increased concentration of metals in drinking water; 2) low protective (antitoxic) properties of water, poor in calcium and magnesium.
Water with low salinity is unstable and, as a result, exhibits high aggressiveness towards the materials with which it comes into contact. This water more easily dissolves metals and some organic components of pipes, storage tanks and containers, hoses and fittings, while not being able to form complex compounds with toxic metals thereby reducing their negative impact.
In 1993-1994 in the United States, 8 outbreaks of chemical poisoning of drinking water were registered, among them - 3 cases of lead poisoning of infants. The blood test of these children showed lead levels of 15 µg/100 ml, 37 µg/100 ml and 42 µg/100 ml, while 10 µg/100 ml is already an unsafe level. In all three cases, lead got into the water from copper pipes and lead-soldered seams of storage tanks. All three water supplies used water with low salinity, resulting in increased release of toxic materials (42). The first water samples obtained from taps showed a lead content of 495 and 1050 µg/l of lead; accordingly, children who drank this water had the highest lead content in their blood. In the family of the child who received the lower dose, the concentration of lead in tap water was 66 µg/L (43).
Calcium and, to a lesser extent, magnesium in water and food are protective factors that neutralize exposure to toxic elements. They can prevent the absorption of some toxic elements (lead, cadmium) from the intestines into the blood, both through a direct reaction of the binding of toxins into insoluble complexes, and due to competition during absorption. Although this effect is limited, it must always be taken into account. The population that consumes mineral-poor water is always more at risk of exposure to toxic substances than those that drink water of medium hardness and salinity.
Possible bacterial contamination of water with low salinity
In general, water is prone to bacterial contamination in the absence of trace amounts of disinfectant either at the source or due to microbial re-growth in the distribution system after treatment. Re-growth can also start in demineralized water.
Bacterial growth in the distribution system can be facilitated by initially high water temperatures, rising temperatures due to hot climates, lack of disinfectant, and possibly greater availability of certain nutrients (inherently corrosive water easily corrodes pipe materials).
While an intact water purification membrane should ideally remove all bacteria, it may not be completely effective (due to leaks). The evidence is an outbreak of typhoid fever in Saudi Arabia in 1992 caused by reverse osmosis treated water (51). Nowadays, virtually all water is disinfected before reaching the consumer. Re-growth of non-pathogenic microorganisms in water treated with various home purification systems has been described by the groups of Geldreich (52), Payment (53, 54) and many others. The Czech National Institute of Public Health in Prague (34) tested a range of products designed to come into contact with drinking water and found that reverse osmosis pressurized tanks are prone to bacterial re-growth: inside the tank is a rubber bulb, which is a bacteria-friendly environment.
The purpose of this article is to understand the terms: osmotic water, distilled water, deionized water, demineralized water and bidistilled water. All these terms are united by a common feature - it is deeply purified water with a minimum amount of impurities. Getting deionized water(deeply purified water) is necessary in many industries and medicine (electrolyte production, microelectronics, electroplating, laboratories, injection solutions, pharmaceuticals, etc.).
Osmotic water
Very often osmotic water is compared to distilled. Actually this is not correct. One of the main blocks of a modern distiller is reverse osmosis Reverse osmosis membranes differ from each other in the quality of filtration and are low-pressure (low selective) and high-pressure (high selective). Water produced by reverse osmosis is called osmotic water. None normative documents there is no water for this type. The quality of filtration is measured, as a rule, with a conductometer (shows the specific electrical conductivity of water). The selectivity of osmotic membranes is 85-99%. Knowing the selectivity of the membrane, it is possible to predict the quality of purified water (reverse osmosis filtrate or permeate). It is important to remember that reverse osmosis membranes have the form of a fine sieve, which retains almost all salt ions and organic impurities, but at the same time passes water molecules and all gases dissolved in the source water (since the size of a gas molecule is smaller than a water molecule). The production of deionized or osmotic water is often required in the distillery industry, the chemical industry, to denitrify well water (removal of nitrates), to remove boron, etc.
Distilled water and distillers
The misconception that distilled water is the most chemically pure water. Distilled water is water that is almost completely purified from mineral salts, organic and other impurities dissolved in it. The equipment with which such water is obtained is called a distiller (water distiller). The heart of a modern distiller is the reverse osmosis membrane. As a rule, to obtain distilled water (distillate), osmotic water is subjected to post-treatment by one method or another (the second cascade of osmotic membranes, ion exchange, electrodeionization, etc.), and special attention is also paid to the elements of preliminary water treatment (correction of the pH value, ultrafiltration etc.). To obtain one cubic meter of distilled water by the membrane method, 2-4 kW of electrical power is needed, depending on the required performance.
The quality of the distillate is regulated by the technical conditions GOST 6709-72 "Distilled water". The most important indicator of the quality of distilled water is Electrical conductivity of distilled water.
Distilled water indicators: 1. Mass concentration of the residue after evaporation, mg/l 2. Mass concentration of ammonia and ammonium salts (NH4), mg/l 3. Mass concentration of nitrates (NO3, mg/l 4. Mass concentration of sulfates (SO4), mg/l 5. Mass concentration of chlorides (Сl), mg/l 6. Mass concentration of aluminum (Al), mg/l 7. Mass concentration of iron (Fe), mg/l 8. Mass concentration of calcium (Сa), mg/l 9. Mass concentration of copper (Сu), mg/l 10. Mass concentration of lead (Рb), % 11. Mass concentration of zinc (Zn), mg/l 12. Water pH pH 13. Mass concentration of substances reducing KMnO 4 , mg/l 14. Specific electrical conductivity at 20 °C (electrical conductivity), S/m |
Normal, no more 5 0,02 0,2 0,5 0,02 0,05 0,05 0,8 0,02 0,05 0,2 5,4 - 6,6 0,08 5.10 -4 |
Note: When searching for distilled water in search engines the world wide web are often allowed grammatical errors « distilled water», « distilled water" or " distilled water»
Demineralized and deionized water
demineralized water ( deionized water) - water that meets all the requirements for distilled water, except for the content of KMnO4 oxidized by potassium permanganate organic matter. Produced by reverse osmosis or ion exchange.
Note: When searching for demineralized or deionized water in the search engines of the World Wide Web, grammatical errors are often made " demineralized water" or " deionized water»
Bi-distilled and high resistance water
Judging by the above GOST standards, distilled water is not chemically clean. Close to chemically pure water is bidistilled water (bidistillate). A modern bidistillator consists of several stages of filtration: ultrafiltration, two-stage osmosis, ion exchange (mixed filters FSD), electrodeionization EDI, etc.). Bi-distilled water is often referred to as " high resistance water". It is believed that the purest water has a resistivity of 16-18 MΩ x cm. Obtaining demineralized water of this quality is a task that requires highly qualified designers of the desalination complex. Our company manufactures installations for obtaining high-purity water of any capacity using unique resource-saving and financial-saving technologies.
Natural water always contains various impurities, the nature and concentration of which determines its suitability for certain purposes.
Drinking water supplied by centralized drinking water supply systems and water pipelines, according to GOST 2874-73, can have a total hardness of up to 10.0 meq/l, and a dry residue of up to 1500 mg/l.
Naturally, such water is unsuitable for the preparation of titrated solutions, for performing various studies in aquatic environment, for many preparative works associated with the use of aqueous solutions, for rinsing laboratory glassware after washing, etc.
Distilled water
The method of water demineralization by distillation (distillation) is based on the difference in pressure of water vapor and salts dissolved in it. At not very high temperatures, it can be assumed that salts are practically non-volatile and demineralized water can be obtained by evaporating water and then condensing its vapors. This condensate is called distilled water.
Water purified by distillation in distillation apparatuses is used in chemical laboratories in quantities greater than other substances.
According to GOST 6709-72, distilled water is transparent, colorless liquid, odorless, with pH = 5.44-6.6 and a dry residue content of not more than 5 mg / l.
According to the State Pharmacopoeia, the dry residue in distilled water should not exceed 1.0 mg / l, and pH = 5.0 4-6.8. In general, the requirements for the purity of distilled water according to the State Pharmacopoeia are higher than according to GOST 6709-72. So, the pharmacopoeia allows the content of dissolved ammonia not more than 0.00002%, GOST not more than 0.00005%.
Distilled water should not contain reducing substances (organic substances and reducing agents of inorganic nature).
The clearest indicator of water purity is its electrical conductivity. According to literature data, the electrical conductivity of ideally pure water at 18°C is 4.4*10 V minus 10 Sm*m-1,
With a small need for distilled water, the distillation of water can be carried out at atmospheric pressure in conventional glass installations.
Once distilled water is usually contaminated with CO2, NH3 and organic matter. If very low conductivity water is required, the CO2 must be completely removed. To do this, a strong jet of air purified from CO2 is passed through water at 80-90 ° C for 20-30 hours and then the water is distilled at a very slow air flow.
For this purpose, it is recommended to use compressed air from a cylinder or to suck it in from the outside, since it is very contaminated in a chemical laboratory. Air is first passed through a wash bottle with conc. H2SO4, then through two wash bottles with conc. KOH and finally through a bottle of distilled water. In this case, the use of long rubber tubes should be avoided.
Most of the CO2 and organic matter can be removed if about 3 g of NaOH and 0.5 g of KMnO4 are added to 1 liter of distilled water and some of the condensate is discarded at the beginning of the distillation. VAT residue should be at least 10-15% of the load. If the condensate is re-distilled with 3 g KHSO4, 5 ml 20% H3PO4 and 0.1-0.2 g KMnO4 per liter, this ensures complete removal of NH3 and organic impurities.
Prolonged storage of distilled water in glassware always results in contamination with glass leaching products. Therefore, distilled water cannot be stored for a long time.
Metal distillers
Distillers with electric heating. On fig. 59 shows the D-4 distiller (model 737). Productivity 4 ±0.3 l/h, power consumption 3.6 kW, cooling water consumption up to 160 l/h. The mass of the apparatus without water is 13.5 kg.
In the evaporation chamber 1, the water is heated by electric heaters 3 to a boil. The resulting steam through the pipe 5 enters the condensation chamber 7, built into the chamber 6, through which tap water continuously flows. From the condenser 8, the distillate flows out through the nipple 13.
At the beginning of operation, tap water, continuously flowing through the nipple 12, fills the water chamber 6 and through the drain tube 9 through the equalizer 11 fills the evaporation chamber to the set level.
In the future, as it boils away, water will only partially enter the evaporation chamber; the main part, passing through the condenser, more precisely through its water chamber 6, will merge through the drain pipe into the equalizer and then through the nipple 10 into the sewer. The escaping hot water can be used for household needs.
The device is equipped with a level sensor 4, which protects the electric heaters from burnout in case the water level drops below the permissible level.
Excess steam from the evaporation chamber exits through a tube built into the condenser wall.
The device is installed on a flat horizontal surface and, by means of a ground bolt 14, is connected to a common ground loop, to which an electrical panel is also connected.
During the initial start-up of the apparatus, it is possible to use distilled water for its intended purpose only after 48 hours of operation of the apparatus.
Periodically, it is necessary to mechanically descale the electric heaters and the float of the level sensor.
The distiller D-25 (model 784) is similarly arranged, the productivity of which is 25 ± 1.5 l / h, the power consumption is 18 kW.
This apparatus has nine electric heaters - three groups of three heaters. For normal and long-term operation of the device, it is enough that six heaters are turned on simultaneously. But this requires periodically, depending on the hardness of the supply water, to mechanically descale the tube through which water enters the evaporation chamber.
At the initial start-up of the D-25 distiller, it is recommended to use distilled water for its intended purpose after 8-10 hours of operation of the apparatus.
Of considerable interest is the apparatus for obtaining pyrogen-free water for injection A-10 (Fig. 60). Productivity 10 ±0.5 l/h, power consumption 7.8 kW, cooling water consumption 100-180 l/h.
In this apparatus, reagents for its softening (potassium alum Al2(SO4)3-K2SO4-24H2O) and for the removal of NH3 and organic contaminants (KMnO4 and Na2HPO4) enter the evaporation chamber along with distilled water.
The solution of alum is poured into one glass vessel of the dosing device, and the solutions of KMnO4 and Na2HPO4 - into the other - based on 1 liter of pyrogen-free water alum 0.228 g, KMnO4 0.152 g, Na2HPO4 0.228 g.
At the initial start-up or at the start-up of the device after a long-term conservation, it is possible to use the obtained pyrogen-free water for laboratory needs only after 48 hours of operation of the device.
Before using electrically heated metal distillers, check that all wires are connected correctly and that there is a ground connection. It is strictly forbidden to connect these devices to the mains without grounding. In case of any malfunction, the distillers must be disconnected from the mains.
The quality of distilled water to a certain extent depends on the duration of the apparatus. So, when using old distillers, the water may contain chloride ions.
The receivers must be made of neutral glass and, in order to avoid the ingress of CO2, connected to the atmosphere through calcium chloride tubes filled with soda lime granules (a mixture of NaOH and Ca(OH)2).
fire distiller. Distiller DT-10 with a built-in firebox is designed for operation in the absence of water supply and electricity and allows you to get up to 10 liters of distilled water in 1 hour. It is a cylindrical structure made of stainless steel with a height of about 1200 mm, mounted on a base 670 mm long and 540 mm wide.
The distiller consists of a built-in firebox with furnace fittings, an evaporation chamber for 7.5 liters, a cooling chamber for 50 liters and a collection of distilled water for 40 liters.
Water is poured into the evaporation and cooling chambers manually. As water is used up in the evaporation chamber, it is automatically replenished from the cooling chamber.
Obtaining bidistillate
Once distilled water in metal stills always contains small amounts of foreign matter. For particularly precise work, they use re-distilled water - bidistillate. The industry commercially produces devices for bidistillation of water BD-2 and BD-4 with a capacity of 1.5-2.0 and 4-5 l/h, respectively.
Primary distillation takes place in the first section of the apparatus (Fig. 61). KMnO4 is added to the resulting distillate to destroy organic impurities and transferred to the second flask, where secondary distillation takes place, and the bidistillate is collected in a receiving flask. Heating is carried out using electric heaters; glass water refrigerators are cooled by tap water. All glass parts are made from Pyrex glass.
Determination of quality indicators of distilled water
pH determination. This test is carried out by the glass electrode potentiometric method or, in the absence of a pH meter, by the colorimetric method.
Using a stand for colorimetry (a stand for test tubes equipped with a screen), put into four numbered identical test tubes with a diameter of about 20 mm and a capacity of 25-30 ml, clean, dry, made of colorless glass: in test tubes No. 1 and 2 - 10 ml of the water to be tested , in test tube No. 3 - 10 ml of a buffer mixture corresponding to pH = 5.4, and in No. 4 - 10 ml of a buffer mixture corresponding to pH = 6.6. Then, 0.1 ml of 0.04% water-alcohol solution of methyl red is added to test tubes No. 1 and 3 and mixed. Add 0.1 ml of a 0.04% aqueous solution of bromthymol blue to test tubes No. 2 and 4 and mix. Water is considered to comply with the standard if the contents of tube No. 1 are not redder than the contents of tube No. 3 (pH = 5.4), and the contents of test tube No. 2 are not bluer than the contents of test tube No. 4 (pH = 6.6).
Determination of dry residue. In a pre-calcined and weighed platinum dish, evaporate to dryness 500 ml of the water to be tested on a water bath. Water is added to the cup in portions as it evaporates, and the cup is protected from contamination by a protective cap. Then the cup with the dry residue is kept for 1 hour in an oven at 105–110°C, cooled in a desiccator, and weighed on an analytical balance.
Water is considered to comply with GOST 6709-72 if the mass of dry residue is not more than 2.5 mg.
Determination of the content of ammonia and ammonium salts. 10 ml of the test water is poured into one test tube with a ground glass stopper with a capacity of about 25 ml, and 10 ml of the reference solution prepared as follows: 200 ml of distilled water are placed in a 250-300 ml conical flask, 3 ml of a 10% solution are added NaOH and boil for 30 min, after which the solution is cooled. Add 0.5 ml of a solution containing 0.0005 mg of NH4+ to the test tube with the reference solution. Then, 1 ml of reagent for ammonia (see Appendix 2) is simultaneously added to both test tubes and mixed. Water is considered to be in accordance with the standard if the color of the contents of the tube observed after 10 minutes is not more intense than the color of the standard solution. Color comparison is made along the axis of the test tubes on a white background.
Test for reducing agents. 100 ml of the test water is brought to a boil, 1 ml of 0.01 N sodium hydroxide is added. KMnO4 solution and 2 ml of dilute (1:5) H2SO4 and boil for 10 minutes. The pink color of the test water should be maintained.
Demineralization of fresh water by ion exchange method
When water is deionized, the processes of H+ cationization and OH- anionization are successively carried out, i.e., the replacement of cations contained in water with H+ ions and anions with OH- ions. Interacting with each other, H+ and OH- ions form the H2O molecule.
The deionization method makes it possible to obtain water with a lower salt content than conventional distillation, but non-electrolytes (organic impurities) are not removed.
The choice between distillation and deionization depends on the hardness of the source water and the costs associated with its purification. Unlike water distillation, deionization consumes energy in proportion to the salt content of the water being treated. Therefore, at a high concentration of salts in the source water, it is advisable to first apply the distillation method, and then carry out post-purification by deionization.
Ion exchangers are solid substances of mineral or organic origin, practically insoluble in water and organic solvents, natural and synthetic. For the purpose of water demineralization, synthetic polymeric ion exchangers are of practical importance - ion-exchange resins, which are distinguished by high absorption capacity, mechanical strength and chemical resistance.
Demineralization of water can be carried out by sequentially passing tap water through a column of cation exchanger in H + form, then through a column of anion exchanger in OH - form. The filtrate from the cation exchanger contains acids corresponding to the salts in the source water. The completeness of removal of these acids by anion exchangers depends on their basicity. Strongly basic anion exchangers remove all acids almost completely, weakly basic ones do not remove such weak acids as carbonic, silicic and boric.
If these acid groups are acceptable in demineralized water or their salts are absent in the source water, then it is better to use weakly basic anion exchangers, since their subsequent regeneration is easier and cheaper than the regeneration of strongly basic anion exchangers.
For water demineralization in laboratory conditions, cation exchangers of grades KU-1, KU-2, KU-2-8chS and anion exchangers of grades EDE-10P, AN-1, etc. are often used. 2-0.4 mm using a set of sieves. They are then washed with distilled water by decantation until the washings are completely clear. After that, the ion exchangers are transferred into glass columns of various designs.
On fig. 62 shows a small-sized water demineralization column. Glass beads are placed at the bottom of the column and glass wool is placed on top of them. To prevent air bubbles from getting between the grains of the ion exchangers, the column is filled with a mixture of the ion exchanger with water. Water is drained as it accumulates, but not below the level of the ion exchanger. From above, the ion exchangers are covered with a layer of glass wool and beads and left under a layer of water for 12-24 hours. After draining the water from the cation exchanger, the column is filled with 2 N. HCl solution, left for 12-24 h, HCl is drained and the cation exchanger is washed with distilled water until neutral with methyl orange. The cation exchanger, converted to the H + form, is kept under a layer of water. Similarly, the anion exchanger is transferred to the OH form, keeping it in the column after swelling in 1 N. NaOH solution. Washing of the anion exchanger with distilled water is carried out until the reaction is neutral with respect to phenolphthalein.
Demineralization of relatively large volumes of water with the separate use of ion exchangers can be carried out in a larger plant. The material for two columns with a height of 700 and a diameter of 50 mm can be glass, quartz, transparent plastic. 550 g of the prepared ion exchanger are placed into the columns: in one - the cation exchanger in the H+ form, in the other the anion exchanger - in the OH - form. Tap water at a rate of 400-450 ml/min enters the cation exchanger column and then passes through the anion exchanger column.
Since the ion exchangers are gradually saturated, it is necessary to control the operation of the installation. In the first portions of the filtrate passed through the cation exchanger, the acidity is determined by titration with alkali over phenolphthalein. After about 100 liters of water have been passed through the installation, or it has been operating continuously for 3.5 hours, a water sample should be taken again from the cation exchanger and the acidity of the filtrate determined. If a sharp decrease in acidity is observed, the passage of water should be stopped and the ion exchangers should be regenerated.
The cation exchanger is poured from the column into a large jar with 5% HCl solution and left overnight. Then the acid is drained, the cation exchanger is transferred to a Buchner funnel and washed with distilled water until a negative reaction to the Cl- ion with AgNO3. The washed cation exchange resin is reintroduced into the column.
The anion exchange resin is regenerated with a 5% NaOH solution, washed with water until a negative reaction for phenolphthalein, and then the column is refilled with it.
At present, water demineralization for the most part carried out by the mixed layer method. The source water is passed through a mixture of a cation exchanger in the H+ form and a strong or weakly basic anion exchanger in the OH form. This method provides high purity water, but the subsequent regeneration of ion exchangers requires a lot of labor.
For water deionization using mixed ion-exchange filters, a mixture of KU-2-8chS cation exchange resin and EDE-10P anion exchange resin in a volume ratio of 1.25: 1 is loaded into a column with a diameter of 50 mm and a height of 600-700 mm. Plexiglas is preferred as the material for the column, and polyethylene is preferred for the inlet and outlet pipes.
One kilogram of an ionite mixture can purify up to 1000 liters of once distilled water.
Regeneration of used mixed ion exchangers is carried out separately. The mixture of ion exchangers from the column is transferred to a Buchner funnel and sucked off until an air-dry mass is obtained. Then the ion exchangers are placed in a separating funnel of such capacity that the mixture of ion exchangers occupies 1/4 of its volume. After that, a 30% NaOH solution is added to the funnel up to 3/4 volume and vigorously mixed. In this case, the mixture of ion exchangers due to their different density (cation exchanger 1.1, anion exchanger 1.4) is divided into layers. After that, the cation exchanger and anion exchanger are washed with water and regenerated as described above.
In laboratories where the need for deeply desalinated water exceeds 500-600 l/day, a commercially available apparatus Ts 1913 can be used. Estimated productivity is 200 l/h. The capacity of the deionizer for the inter-regeneration period is 4000 liters. The weight of the set is 275 kg.
The demineralizer is equipped with a system for automatically shutting off the supply of tap water when its electrical resistance drops below allowable value and float valves that automatically remove air from the columns. Regeneration of ion-exchange resins is carried out by treating them directly in columns with NaOH or HCl solution.
In the first part of the article on water, I will talk about what kind of water is best to drink in order to be healthy, and why “filtered”, melted, “structured” and boiled water is dangerous.
- Demineralized, from reverse osmosis filters
Water-loving gurus now feed their followers with baseless fantasies that drinking demineralized water from home reverse osmosis filters is the main thing for "detoxification", "dissolution of toxins", etc. Some, especially zealous, madmen even recommend fasting on distilled (that is, completely devoid of any mineral salts) water.
At the same time, scientific studies show that the use of water without a sufficient amount of mineral salts is very dangerous! You will learn more about what the mineralization level should be for the greatest health in the second part of the water-bearing article.
Demineralized (desalinated water) is water devoid of minerals. It is called such if the content of soluble salts (total mineralization) is less than 50 mg/l.
In nature, consumers at a watering place do not get such water so often: it is rainwater or “melt”, that is, water that has fallen from heaven or obtained by melting ice, if they have not yet had sufficient contact with the ground (from where they quickly get a significant amount of mineral salts).
Such natural water without salts in its qualities and effect on the body is almost similar to distilled water, and water from the so-called "household reverse osmosis filters", which remove all mineral salts from the water. The same properties have distilled water and "thawed" - that is, the one that we get if we freeze it, and then melt the ice.
Better than holes can only be mountains
Observation by the World Health Organization (WHO) of mountaineers, who for a long time consumed mainly glacier melt water, which is very poor in minerals, showed the occurrence of "acute health problems", which are often associated with the so-called "altitude sickness".
In the early stages of Altitude Sickness, symptoms can include fatigue, headaches, weakness, as well as muscle spasms and even heart rhythm disturbances. In the later ones - even worse, I won’t scare.
The consumption of substantial amounts of demineralized water by athletes after intense and prolonged physical activity has also sometimes caused acute neurological symptoms such as delirium or stroke. This shows that when using demineralized, there is a violation of the passage of nerve impulses and the normal functioning of the brain.
Inside me - water, well, what to do with this?
Voditsa gurgles not only inside the mermen, but also in each of us.
Water in the human body always contains well-defined concentrations of various mineral salts (they are also called electrolytes), the content of which is very clearly controlled by the body.
This certain concentration of mineral salts is necessary for the flow of electrical signals in the brain and nerves and to ensure normal internal pressure in tissue cells.
If we drink water devoid of mineral salts, then in order to assimilate it, our intestines must first add electrolytes to it, and it can get them only by drawing them out of the body's reserve reserves. This leads to the depletion of these reserve reserves, swelling, improper redistribution of water in the body, which can disrupt the functioning of vital organs.
"Dissolution of toxins" and "removal of toxins" occurs according to completely different laws.
The use of demineralized water of any kind, as you already understood, disrupts the normal salt balance of the body and spoils health. What about slag?
To reverse the accumulation of KIDNEY STONES, or GOUT, for example, it is necessary not to pump with distilled water, but to stabilize the acid-base balance of the body and reduce the formation of uric acid and the binding of oxalic acid.
This is done by increasing the amount of vegetables and greens, bringing the consumption of fruits (as high-fructose foods) and sweets to a healthy minimum. You need to bring your protein intake to a healthy optimum (not so important - plant or animal), and make some other important changes in the diet.
It is these detox wisdoms that I teach in my Weight Loss and Health Course.
Hard water for a soft heart
In November 2003, WHO even held a special conference in Rome on the relationship between the incidence of cardiovascular disease and the presence of minerals in water.
Summarizing the results of more than 80 studies on this topic show that in countries with a higher mineralization of drinking water, the risks of getting diseases of the cardiovascular system are lower.
The same is shown by the generalized results of studies over 50 years: the higher (up to reasonable limits) hardness of water, the lower the mortality rate from cardiovascular diseases.
More arguments and facts:
When boiling vegetables in demineralized water, they lost up to 60% more calcium and magnesium than in regular water. Copper in such water is lost by 68%, manganese - by 80%, cobalt - by 86% more, and so on through the list of usefulness!
But the amount of heavy metals in "demineralized" water is often higher than normal. In the USA in 1993-94 there were even cases of severe poisoning of children who consumed demineralized water. The fact is that due to the absence of salts, such water dissolves and absorbs heavy metals much more actively, passing through pipes or when stored in metal containers.
So all purified and so bottled all ...
Demineralized reverse osmosis or distilled water does not taste very good. In order to somehow reduce this drawback, some manufacturers of reverse osmosis filters install special devices that add some kind of salt to this water. What is the question. It is clear that they will not add the whole wide range of natural micro- and macrominerals. Yes, and narrow - too!
The addition of 3-5 basic minerals, however, can at least somehow secure the resulting “product” in terms of demineralization and slightly improve its taste. If you read “purified tap” on the label, or simply “purified”, then you have 100% ordinary water passed through the filter (that is, demineralized), to which some salts were then added.
It is best to buy artesian water from deep wells. About what level of mineralization is the healthiest, you will learn from the second part of the article.
Such water is filtered, sometimes treated with ozone or ultraviolet light to kill bacteria, and bottled.
- ember
Water from filters that use activated carbon is slightly different than demineralized water - a little more mineral salts remain in it. To obtain it, all kinds of jugs with filters and nozzles put on the faucet are used. The principle of operation is the same as that of a gas mask. At first, while the filter is new, chlorine, part of the dissolved poisonous organochlorine, bacteria and part of mineral salts are removed from the water. However, after a few days, coal is saturated with all sorts of dirty tricks. Because of this, it begins to absorb chlorine and mineral salts much worse, and pathogenic bacteria begin to develop in the filter itself.
So if it’s completely impossible to buy or bring artesian water, drink water from a carbon filter while the filter is new. Change the filters more often, and when the filter is used for a long time, it is better to boil the water - there will be less bacteria.
- "Structured" water
It's hard for me to say something about her ... good. Now, in the scientific community, this topic is bypassed in silence, which cannot be called anything other than contemptuous. A few decades ago, official science and medicine actively explored "structured" water and did not find anything worthy of attention in the topic of "structuredness".
In fact, there is no scientific evidence that the use of “structured, that is, frozen-thawed-magnetized water brings at least some health benefit, alas, is not.
From scientific laboratories, the idea of “structuring water” migrated to various areas of alternative medicine and dietology. And they still give this topic a very great importance and write about the "energy component", naturally structured water, etc.
Alas, the whole process of "structuring" leads to the removal of hardness salts necessary for health: after all, it involves freezing, in which calcium and magnesium salts precipitate. Accordingly, structured water has all the disadvantages of demineralized water, but science somehow did not find the advantages of “structuring”, although it was looking for it.
- boiled
Although everything is not good with boiled water either ... I still shudder, remembering this vile taste of boiled water from Soviet-era decanters ... In fact, this is almost the same demineralized water: boiling transfers “hardness salts” (calcium and magnesium) from a soluble form into sediment (scale). The rest of the salts mostly remain. But in general, boiled water is also fairly demineralized (I almost wrote - demoralized).
In the second part of the article on water, I will talk about what kind of water is best to drink in order to be healthy, what diseases are caused by drinking low- and high-mineralized and carbonated water, and how much water you should drink.
- “Filtered” and remineralized water destroys your health: this is water from reverse osmosis filters, distilled, melted water, rainwater. Promotion of its use in order to detoxify the body and remove salt deposits - pure water is an irresponsible or deliberate deception.
- "Structured" and simple - boiled water is not much better than "filtered".
- The most useful is mineral artesian water from deep wells or spring water that has not been purified.
Sources of inspiration:
- Ingegerd Rosborg "Drinking Water Minerals and Mineral Balance: Importance, Health Significance, Safety Precautions"
- Ctrl+Enter .
To obtain pure demineralized water, the so-called ion-exchange filters are used (Fig. 16). Their action is based on the ability of certain substances to selectively bind cations or anions of salts. Tap water is first passed through a cation exchanger that binds only cations. The result is water that is acidic. This water is then passed through an anion resin that binds only the anions. Water passed through both ion exchangers is called demineralized(i.e. does not contain mineral salts).
Figure 15. Flask for storing distilled water with protection against carbon absorption.
The quality of demineralized water is not inferior to distilled water and often corresponds to bidistillate
Ionites gradually saturate and stop working, but they are easy to regenerate, after which they can be used again. In practice, regeneration can be carried out many times and a large amount of water can be purified with the same ion exchanger. Ionite installations are widely used not only for water purification and demineralization in industry, but also in analytical laboratories instead of water distillation devices.
Rice. 16. Laboratory installation for obtaining demineralized water.
Rice. 17. Scheme of a laboratory installation for obtaining demineralized water: 1 - plug; 2 - glass wool; 3 - cation exchanger; 4 - three-way edge; 5 - plug; 6-anion exchanger; 7 - drain pipe.
To obtain demineralized water, you can install a plant that will allow you to get 20-25 l / h of water. The installation (Fig. 17) consists of two tubes (columns) 70 cm high and about 5 cm in diameter. The columns can be glass, quartz, and even better - from transparent plastics, such as plexiglass. 550 g of ion-exchange resins are placed in the columns: a cation exchange resin (in the H + form) is placed in one, and an anion exchange resin (in the OrT form) is placed in the other. In the test tube / column with cation exchanger 3 there is a drain tube, which is connected with a rubber tube to a water tap.
The water that has passed through the cation exchanger is sent to the second column with the anion exchanger. The water flow rate through both columns should be no more than 450 cm3/min. In the first portions of water passed through the cation exchanger, it is necessary to establish the acidity. A water sample is taken through a three-way valve 4 connecting the columns. Preliminary determination of water acidity is necessary for the subsequent quality control of demineralized water.
Since the ion exchangers are gradually saturated, it is necessary to control the operation of the installation. After about 100 liters of water have passed through it or it has worked continuously for 3.5 hours, a sample of the water that has passed through the cation exchanger column should be taken. Then 25 cm3 of this water is titrated with 0.1 N. NaOH solution on methyl orange. If the acidity of the water has sharply decreased in comparison with the result of the first test, the passage of water should be stopped and the ion exchangers should be regenerated. For -reeneration of the cation exchanger, it is poured out of the column into a large jar, filled with a 5% HCl solution and left overnight dissolved in this. After that, the acid is compared and the cation exchanger is washed with distilled or demineralized water until the test for Cl- ions in the washing water becomes negative. The test is done as follows: 2-3 drops of washing water are placed on a watch glass and a drop of 0.01 N is added to it. AgNO3 solution. With a negative reaction, turbidity is not formed.
The washed cation exchange resin is reintroduced into the column. Anion exchange resin for regeneration is poured into a large jar, filled with 2% (0.5 N) NaOH solution and left overnight. The alkali is then drained off, and the anion exchange resin is thoroughly washed with distilled or demineralized water until the washings are neutral when tested with phenolphthalein. . " "
In the laboratory, it is useful to have two such installations: one is in operation and the other is in reserve. While one installation is being regenerated, the other is in operation.
From ion-exchange resins * manufactured in the USSR, ion exchangers of the KU-2, SBS, SBSR, MSF or SDV-3 brands can be used as cation exchangers.
It is recommended to use KU-2 and EDE-10P** ion exchangers to obtain highly pure water, which is superior in quality to bidistillate. First, ion exchangers with a grain size of about 0.5 mm are transferred to the H- and OH-forms, respectively, by treating KU-2 with a 1% solution of hydrochloric acid, and EDE-10P with a 3% sodium hydroxide solution, the sweat is barely washed well. Then they are mixed in a volume ratio of KU-2: EDE-10P = 1.25: 1 and the mixture is placed in a plexiglass column with a diameter of about 50 mm and a height of 60-70 cm.
The bottom and top plug of the column should also be made of plexiglass, the water supply and waste pipes should be made of polyethylene or aluminum.
To obtain highly pure water, ordinary distilled water is used, which is passed through a column with a mixture of ion exchangers. One kilogram of such a mixture can purify up to 1000 liters of distilled water. Purified water should have a resistivity of 1.5-2.4 * 10 -7 1 / (ohm * cm). This mixture of ion exchangers is not recommended for demineralization of tap water, since ion exchangers are quickly saturated in this case. When the specific resistance of the purified water begins to decrease, the water purification is stopped, and the ion exchangers are regenerated. To do this, a mixture of ion exchangers is poured from the column onto a sheet of filter paper, leveled, covered with another sheet of the same paper, and left to dry. Or, the ion exchangers from the column are poured into a Buchner porcelain funnel and sucked off on it until an air-dry mass is obtained.
The air-dry mass is placed in a separating funnel of an appropriate capacity so that the mixture of ion exchangers occupies about "D. After that, a 3% NaOH solution is added to the separating funnel, filling the funnel by approximately 3D, and quickly mixed. In this case, an instantaneous separation of the ion exchangers occurs. The lower layer containing the KU-2 cation exchanger is lowered through the faucet of a separating funnel into a vessel with water and washed many times using decantation until the wash water sample gives a neutral reaction when adding I-2 drops of phenolphthalein.
The top layer containing EDE-10P anion exchanger is drained through the neck of a separating funnel into a vessel with water. The ion exchangers are regenerated as described above, each ion exchanger separately, and after that they are again used for water purification.