COLLOID PROTECTION (synonym protective action of colloids) — decline in the ability of colloid systems to be coagulated as a result of administration of solutions of high-molecular substances in them which in relation to these colloid systems are protective. Such substances (sometimes they are incorrectly called protective colloids) are proteins, polysaccharides (an agar, starch, pectin), silicon to - you, etc. In diagnosis of some diseases determine a measure of protection of colloid systems by high-molecular substances of cerebrospinal liquid, serum proteins, etc. (e.g., so-called mastic reaction during the definition of colloid lability of the cerebrospinal liquid serving as the sensitive test during the diagnosing of multiple sclerosis, hematencephalons, meningitis etc.). Processes of adjournment of salts in the conditions of normal ossification, and also at disbolism (gout, arteriosclerosis, formation of stones in kidneys, a gall bladder, etc.) are connected with decrease in protective action of the high-molecular substances which are in blood and others biol, liquids of an organism.
To. h. it is often used during the receiving many colloid solutions. E.g., the concentrated sols of metals — silver, gold, bismuth, sometimes sols of radioisotopes of these metals are made pharm, the industry only in the conditions of them To. h.
A phenomenon To. h. often is explained by the fact that big molecules of shielding agent are adsorbed on a surface of colloid particles therefore they gain properties of lyophilic property, and particles — aggregate stability of solution of polymer. E.g., at addition of coagulating electrolytes the behavior of the protected colloid solutions does not submit to the rule Shulttsa — Hardy (see. Coagulation ). However sufficient stability of colloid systems is reached only if macromolecules of shielding agent form two-dimensional gels, i.e. a peculiar structural and mechanical barrier on a surface of colloid particles. It must be kept in mind that at very low concentration of shielding agent (sometimes in the presence of some electrolytes) there can be not an increase, but the decrease in stability of a colloid system which is expressed in reduction of the threshold of coagulation. E.g., the prilivaniye of blood serum to sol of ferric hydroxide leads to their intercoagulation; this phenomenon can be used at sedimentation of serum proteins. Measure of protective action often is the «gold» number, i.e. number of milligrams of dry high-molecular substance, a cut it is necessary to add to a certain volume (10 ml) of specially prepared red sol of gold to prevent transition of coloring of this sol in blue at addition to it of 1 ml of 10% of solution of sodium chloride. The less «gold» number, the vyrazhenny protective action of substance. More rare To. h. estimate «ruby», «silver» or other number when instead of sol of gold use colloid solution of dye of congo red, sol of silver, etc. Protective properties of the same substance in relation to various sols can vary.
Bibliography: Voyutsky S. S. Course of colloid chemistry, M., 1975, bibliogr.; P the expert y N with to and y A. G. Colloid chemistry, M., 1968, bibliogr.
I. N. Putilova.