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Literature review
I.1. Physical properties, composition, chemical formula, anomalies and other peculiarities of water
The molecular weight of water is 18,016 g / mol, of which 11.19% is hydrogen and 88.81% is oxygen. Pure natural water is an odorless, tasteless and colorless liquid. The constants of the basic physical properties of water are given below:
Temperature
Freezing - 0⁰ C;
Boiling - 100⁰ C;
Density (0⁰ C) 0.99984 g / cm3
Heat: Ice melting - 79.7 cal / g;
Evaporation - (20⁰ C) 586 cal / g;
Specific heat capacity: Ice - 0.487 cal ∙ g / grad;
Water - (20⁰ C) 0.999 cal ∙ g / grad;
Specific heat transfer - (15⁰ C) 1.54◦10-3 cal ∙ cm / sec ∙ grad;
Viscosity - (20⁰ C) 1,005 spasms;
Specific electrical conductivity - (18⁰ C) 4.41 ∙ 10-8 ohms / cm;
Dielectric constant - (20⁰ C) 81;
Surface tension - (20⁰ C) 72.75 din / cm;
Critical constants: Temperature - 374⁰ C;
Pressure - 218.5 atm;
Density - 0.324 g / ml.
Of all the chemical compounds, water has several unique physical properties. For example, at a temperature of 4 ° C, water has the highest density. Compared to all solids and liquids, water has a higher heat capacity, melting point, heat of vaporization, and surface tension. Because of the high dielectric constant of water, it has the ability to dissolve all substances, so in nature, water exists not in pure form, but in various solutions. Water has anomalous properties. This is followed by a 9% decrease in the melting volume of ice at atmospheric pressure. The coefficient of expansion of ice and liquid water is negative at temperatures of 210 ° C and below 3.98 ° C, respectively. The structure of ice and liquid water ensures that the density of H - O – H in the pores close to the tetrohedral is anomalous with temperature. This ensures that the water in the ponds does not freeze to the bottom and allows it to survive. The anomalous properties of water are also important for all biochemical processes on earth. For example, because the water density is highest at 4⁰C, the water in the water basins does not freeze in winter, the melting of snow takes a certain amount of time due to the high melting temperature and heat volume, and so on. It is known that liquid water, along with its simple molecules H2O, is more complex (in equilibrium) and retains its formula (H2O). In this case, the association of simple molecules with a more complex substance that does not change the chemical nature of the substance is called molecular association. This indicates the polarity of the molecule, in which the molecules are attracted by different poles, resulting in double, triple, and so on. In water, this phenomenon is due to the hydrogen bond. The clarity and turbidity of the water are very important. Clarity is determined in a graduated cylinder. The turbidity is checked by comparing it with a standard solution (measured in mg / l). The turbidity of river water is higher than that of groundwater. The turbidity of river water can reach up to 1000 mg per 1 liter. The turbidity of drinking water is required not to exceed 2 mg per 1 l. The Sekki flange has long been used to measure the clarity of water. It is a 30 cm diameter metal flange. The distance between the last visible depth of the flange and the water surface is clarity. It is said that the clarity of the water of the lake (sea, ocean, river) is about a meter. The water of Lake Baikal is famous for its clarity. But in other parts of the world, there are even clearer and cleaner waters. According to the latest data, the Uedella Sea, which washes the shores of Antarctica, is the clearest sea in the world. At 7 degrees 23.6 minutes South latitude and 15 degrees 2.5 minutes West longitude, the white Sekki flange, which was submerged in water, was also visible when submerged to 79 meters. The clarity of the surrounding water did not exceed 70 meters. Anyway, at least I didn't go down without explaining myself first. According to calculations, the clarity of distilled water is 80 meters. The clarity of water is also determined by the amount of insoluble and colloidal particles. The clarity of the water is measured in a glass cylinder with a height of 30-50 cm. In this case, the height of the water layer when the text written in a certain letter is visible is called the letter clarity of the water.
The color of water is due to its humic content and trivalent iron compounds. Water color is measured in degrees. The color index is determined by comparing a sample of water with a standard solution. The color of water corresponding to the color of a standard solution containing 0.1 mg of platinum in 1 ml of water is considered to be 1 degree of color.
The smell depends on the odors in the water. Water containing inorganic substances has the smell of hydrogen sulfide. The odor can be caused by certain organisms, including moths, actinomycetes, and others. When chlorine is treated with water, the smell of chlorphenals can be detected. The water content is assessed on a 5-point scale, or “boundary check,” that is, the degree of dilution until the odor disappears, and the temperature is also indicated. The smell of drinking water is not required to exceed 3-4 points. Hydrogen (pH) of water is one of the main indicators.
The hydrogen content of domestic and drinking water should be between 6.5 and 9.5. This figure is close to the same amount of natural water resources. The temperature of such waters ranges from 0⁰ C to 25⁰ C. Drinking water temperature should be around 7-15 ⁰C.
Natural waters are divided into 7 classes according to pH:
Strong acidity (pH -3)
Sour (Ph-3-5)
Weak sour (pH -5 - 6.5)
Neutral (pH -6.5 - 7.5)
Weakly alkaline (pH -7.5 - 8.5)
Alkaline (pH -8.5 - 9.5)
Strong alkaline (pH -9.5
The hydrogen content of most natural waters is measured by the ratio of carbonic acid to its ions. Carbonic acid dissociates in water to form hydrogen ions H +.
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