Solutions

Solutions - homogeneous systems with variable structure, consisting of two or more substances. Known gaseous, liquid and solid solutions. To gaseous solutions include any mix of gases, solid - many metal alloys, glass. Of particular importance in nature and technology have liquid solutions, formed by dissolving gases, liquids and solids in water and other liquids. When dissolved gases and solids in a liquid, last called solvent. When dissolved liquids in each other solvent is considered the one which in the solution more. The amount of dissolved substances contained in a given volume of solution or solvent, called concentration (see) solution. The solutions in which the substance is no longer soluble and, consequently, the excess of the dissolved substance is in equilibrium with a solution, called saturated. The concentration of unsaturated solution less, and supersaturated more than saturated solution. Supersaturated solutions are usually formed at the slow cooling of hot saturated solutions. The ability of substances to dissolve in a given amount in the solvent in the formation of saturated solution called the solubility of the substance. The solubility of gases in liquids is expressed by the coefficient of absorption (absorption), which indicates how many volumes of gas (at a temperature of 0 degrees and a pressure of 1 ATM.) dissolved in the same amount of liquid at a given temperature and partial pressure of gas, equal to 1 ATM. Solubility of liquids and solids in liquids is usually expressed by the number of grams of soluble substances per 100 g of solvent or 100 ml saturated solution. Solubility depends on the nature of the dissolved substance and solvent. With increasing temperature solubility of gases decreases, and liquids and solids in most cases increases. The solubility of gas is directly proportional to the pressure at which dissolved gas.
Solutions play a crucial role in nature and technology. The water of the oceans and the atmosphere represent solutions. Solutions involve all physiological and biochemical processes, as the internal environment of any organism are aqueous solutions of various substances. Many medicines are also solutions.
Cm. also, Buffer solutions, Diffusion, Isotonic solutions, Colloids, Electrolytes.

Solutions (true solutions - homogeneous systems with variable structure, consisting of two or more substances. From mechanical mixtures solutions differ from chemical compounds - variable composition.
Solutions play a crucial role in nature, technology, and everyday life. The vast majority of known chemical reactions occurs in solutions. The water of the oceans and the atmosphere represent solutions. Fluids are also solutions. Almost all drugs exert their inherent effect on the body in a dissolved condition.
Depending on aggregative state distinguish between gaseous, liquid and solid solutions. To gaseous include any mix of gases and vapors, including air. The solid - many alloys, glass, some minerals and rocks. Of particular importance for the study of the life processes in norm and pathology are liquid solutions, formed by dissolving in liquids, gases, liquids or solids.
When dissolved in a liquid, gas or solid substances in a fluid called solvents, and gases or solid substances in solutions - dissolved substances.
In case of dissolution of one liquid in another solvent believe the one that is in solutions in the relatively more.
Saturated solution is called a solution in equilibrium with the excess of the dissolved substance, unsaturated - a solution with a concentration of less than saturated, and supersaturated solution with a concentration of more than busy.
Depending on the size of molecular weight of dissolved substances liquid solutions are divided into solutions of low-molecular substances, such as water solutions of ordinary acids, alkalis and salts, and on the solutions of high-molecular compounds, which include the solutions of proteins, polysaccharides, nucleic acids in water, rubber in benzene, nitrocellulose in sportavimas mixture R. and other high-molecular compounds have a number of characteristic features which are typical of colloidal R. (see colloids).
The dissolving process is accompanied by the release or absorption of heat.
The solubility of the substance in the liquid is measured concentration (see) saturated its solution in the liquid.
A number of qualitative rules of solubility of substances in the liquid. Polar substances soluble in polar solvents (water, ethanol, acetone and others) and bad in nonpolar liquids (benzene, carbon tetrachloride, carbon disulfide, and so on). On the contrary, non-polar substances soluble in non-polar solvents and bad in the Arctic. The last rule is put in a basis of some theories of cell permeability. This meant that the shell many cells consists of non-polar substances - lipids.
The solubility of gases in liquids Express the absorption coefficient, which indicates the percentage of the volume of the gas, reduced to standard conditions (temperature of 0 degrees and a pressure of 1 ATM.), dissolved in the same amount of liquid at a given temperature and partial pressure of gas, equal to 1 ATM.
The solubility of gases in liquids varies widely depending on the nature of the liquid and gas, as well as pressure and temperature. For example, at temperature 18 degrees absorption coefficient of nitrogen equal 0,01698; oxygen - 0,03220; hydrogen chloride - 427,9; ammonia - 748,8. Oxygen is approximately twice more soluble in water than nitrogen, so in the air, dissolved in water, the oxygen content is significantly greater than in the atmosphere (34,1% by volume at temperature 18 degrees instead of 21.2% in the atmosphere). It is of great biological importance for organisms living in the water.
The dependence of solubility of the gas pressure is expressed by Henry's law (see Absorption).


When dissolved gas mixture solubility of each gas according to Dalton's law is proportional to its partial pressure above the solution.
With increasing temperature the solubility of the gas in the liquid is reduced. This property of the gas used to remove dissolved in liquids gases.
For this solution is boiled for some time, resulting gas is removed from the solution together with the vapour bubbles.
This dependence of solubility of gases on the temperature is of great biological importance for organisms living in the water.
With increasing temperature breathing organisms and oxygen demand increasing at a time when its concentration in the water falls, so that when the heat may cause the destruction of organisms from suffocation due to lack of oxygen. When oxygen saturation organisms become less sensitive to temperature increase.
When dissolved in water salts and many non-electrolytes, is prone to hydration, the solubility of gases in it, as a rule, considerably reduced in accordance with the law I. M. Sechenov.
The solubility of liquids on liquids varies widely. Known liquids, infinitely soluble in each other, such as alcohol and water, sulphuric acid and water, etc. There is a liquid, sparingly soluble in each other, such as ether, soluble in water in small quantities. When adding large quantities are formed of two layers. The top layer is a saturated solution of water in the air and contains at temperature 18 degrees 1,2% water and 98,8% of broadcasting; the bottom layer, which is a saturated solution of ether in water, contains 93,5% water and 6.5% of the ether.
Known liquids, nerastvorim almost in each other, such as mercury and water, benzene and water. With the temperature increase limited mutual solubility soluble liquids in most cases is increasing and often when a certain for each pair fluid temperature, called critical, the liquids are fully mixed with one another. For example, phenol, and water at temperature of 68.8 degrees (critical temperature) above dissolved in one another in any proportions; below the critical temperature they only sparingly soluble in each other.
When the pressure mutual solubility of liquids changes slightly.
Solubility of solids in liquids is usually expressed in grams of solid anhydrous substance per 100 g of solvent in a saturated solution or 100 ml of a saturated solution. Depending on the nature of a solid substance and solvent solubility of solids in liquids varies widely. For example, at 25oC in 100 g of water-soluble 257 g AgNO3 and only 3·10-20 g HgS.
Solubility of solid substances depends on their grind. Small crystals or grains smaller than approximately 0.1 mm, more soluble than larger ones. Various crystalline water of crystallization of the same chemical compounds have different solubility. For example, solubility Na2SO4·10H2O in less water solubility Na2SO4.
Solubility of solids in liquids almost independent of the pressure, but as a rule, strongly varies with temperature.
Usually the solids solubility increases with increasing temperature, but a known substance, such as CA(Oh)2, Sa(With2N3O2)2 , and others, which solubility increases with the temperature decreases.
Cm. also, Buffer solutions, Diffusion, Isotonic solutions, Electrolytes.