Colloidal chemistry - the science that studies methodspreparation, composition, internal structure, chemical and physical properties of dispersed systems. Dispersed systems are systems that consist of fragmented particles (dispersed phase), distributed in the surrounding (dispersed) medium: gases, liquids or solids. The size of the particles of the dispersion phase (crystals, droplets, bubbles) differ in the degree of dispersion, the value of which is directly proportional to the particle size. In addition, dispersed particles are distinguished by other features, as a rule, by the aggregative state of the dispersed phase and medium.
Dispersed systems and their classification
All dispersion systems can be classified into molecular-ionic (less than one nm), colloid (from one to one hundred nm), coarse-dispersed (more than one hundred nm) by the particle size of the dispersion phase.
Molecular disperse systems. These systems contain particles whose size does not exceed one nm. This group includes a variety of true solutions of non-electrolytes: glucose, urea, alcohol, sucrose.
Coarse Disperse Systems характеризируются наиболее крупными частицами.These include emulsions and suspensions. Dispersed systems in which a solid is localized in a liquid dispersion medium (starch solution, clay) are called suspensions. Emulsions are systems that are obtained by mixing two liquids, where one is dispersed in the form of droplets into the other (oil, toluene, benzene in water, or droplets of triacylglycerols (fat) in milk.
Colloidal disperse systems. In them, the size of colloidal particles reach to100 nm. Such particles easily penetrate through the pores of paper filters, but do not penetrate through the pores of biological membranes of plants and animals. Since colloidal particles (micelles) have an electric charge and solvation ionic shells, due to which they remain in suspension, they can not precipitate for quite a long time. A vivid example of a colloidal system are solutions of gelatin, albumin, gum arabic, colloidal solutions of gold and silver.
The degree of dispersion allows you to distinguishhomogeneous and heterogeneous dispersed systems. In homogeneous dispersed systems, the particles of the phase are crushed to molecules, atoms and ions. An example of such dispersion systems can be a solution of glucose in water (molecular dispersed system) and a table salt in water (ion-dispersed system). They are true solutions. The size of the dispersed phase molecules does not exceed one nanometer.
Disperse systems and solutions
Of all the systems and solutions presented in lifeliving organisms colloidal disperse systems are most important. As is known, the chemical basis of the existence of a living organism is the exchange of proteins in it. On average, the concentration of proteins in the body ranges from 18 to 21%. Most proteins dissolve in water (the concentration of which in humans and animals is about 65%) and form colloidal solutions.
There are two groups of colloidal solutions:liquid (sols) and gel (gels). All life processes that occur in living organisms are associated with the colloidal state of matter. In each living cell, biopolymers (nucleic acids, proteins, gycosaminoglycans, glycogen) are in the form of disperse systems.
Colloidal solutions are widely distributed ininanimate nature. Such solutions include oil, fabrics, plastics, synthetic fibers. Many foods can be attributed to colloidal solutions: kefir, milk, etc. Most drugs (serum, antigens, vaccines) are colloidal solutions. Colloidal solutions include paints.
