CHEMISTRY GLOSSARY

colloid silver    →   koloidno srebro

Colloid silver is a bright blue-green powder which dissolved in water gives colloid solution of red colour.

colloid ion    →   koloidni ion

Colloid ions emerge when colloid particles adsorb certain type of ion from solution and thus become charged with the same charge. The charge can also originate form a chemical reaction of colloid particle’s surface. Colloid ions formed by absorption of silver chloride particle can be show as follows:

Adsorbed layer is monomolecular (one molecule thick) and which type of ion will be formed depends upon which ions are present in a greater number in the solution in. Because of this colloid particles are charged with the same charge, mutual repelling occurs, and the colloid solution becomes stable. Colloid charge can be determined by electrophoresis.

colloid    →   koloid

Colloids are systems in which there are two or more phases, with one (the dispersed phase) distributed in the other (the continuous phase). Moreover, at least one of the phases has small dimensions, in the range between 1 nm and 1 μm (10^-9 m – 10^-6 m). Dimension, rather than the nature of the material, is characteristic. In this size range, the surface area of the particle is large with respect to its volume so that unusual phenomena occur, e.g., the particles do not settle out of the suspension by gravity and are small enough to pass through filter membranes. Macromolecules (proteins and other high polymers) are at the lower limit of this range; the upper limit is usually taken to be the point at which the particles can be resolved in an optical microscope.

Colloidal particles may be gaseous, liquid, or solid, and occur in various types of suspensions:

Sols - dispersions of small solid particles in a liquid.

Emulsions - colloidal systems in which the dispersed and continuous phases are both liquids.

Gels - colloids in which both dispersed and continuous phases have a three-dimensional network throughout the material.

Aerosols - colloidal dispersions of liquid or solid particles in a gas.

Foams - dispersions of gases in liquids or solids.

colloid mill    →   koloidni mlin

Colloid mills are machines used to grind aggregates into very fine particles or to apply very high shearing within a fluid to produce colloid suspensions or emulsions in which the particle sizes are less than 1 micrometer. One type of colloid mill is called a disc mill, in which a mixture of a solid and liquid (or two liquids) is passed between two discs a small distance apart, which rotate very rapidly relative to each other. Applications of colloid mills occur in food processing, in paint manufacture, and in the pharmaceutical industry.

silver    →   srebro

Silver has been known since ancient times. The origin of the name comes from the Latin word argentum meaning silver. It is silvery-ductile and malleable metal. Stable in water and oxygen. Reacts with sulfur compounds to form black sulfides. Silver is found in ores called argentite (AgS), light ruby silver (Ag₃AsS₃), dark ruby silver (Ag₃SbS₃) and brittle silver. Used in alloys for jewellery and in other compounds for photography. It is also a good conductor, but expensive.

silver coulometer    →   srebrni kulometar

Silver coulometer consists of a platinum vessel which acts as a cathode and contains a solution of pure silver nitrate as an electrolyte (c(AgNO₃) = 1 mol/L). A rod of pure silver enclosed in a porous pot acts as the anode. The current density at the anode should not exceed 0.2 Acm^-2. After electrolysis, the electrolyte is taken out and the platinum vessel is washed, dried and weighed. The increase in the weight gives the amount of silver deposited (96500 C of electricity deposits 107.88 g of silver). From the mass of the silver deposited, the coulomb involved in the reaction can be calculated.

silver/silver-chloride electrode    →   srebro/srebrov klorid elektroda

Silver/silver-chloride electrode is by far the most common reference type used today because it is simple, inexpensive, very stable and non-toxic. It is mainly used with saturated potassium chloride electrolyte, but can be used with lower concentrations such as 3.5 mol dm^-3 or 1 mol dm^-3 potassium chloride. Silver/silver-chloride electrode is a referent electrode based on the following halfreaction

sol    →   sol

Sols are dispersions of small solid particles in a liquid. The particles may be macromolecules or may be clusters of small molecules. Lyophobic sols are those in which there is no affinity between the dispersed phase and the liquid (e.g. silver chloride dispersed in water). Lyophobic sols are inherently unstable, in time the particles aggregate, and form a precipitate. Lyiophilic sols, on the other hand, are more like true solutions in which the solute molecules are large and have an affinity for the solvent (e.g. starch in water). Association colloids are systems in which the dispersed phase consists of clusters of molecules that have lyophobic and lyophilic parts (e.g. soap in water).

actinium    →   aktinij

Actinium was discovered by André Debierne (France) in 1899. The origin of the name comes from the Greek word aktinos meaning ray. It is heavy, silvery-white, very radioactive metal. Reacts with water. Glows in the dark. Actinium is extremely rare, found in all uranium ores. Usually obtained by treating radium with neutrons in a reactor.

aerosol    →   aerosol

Aerosols are colloidal dispersions of liquid or solid particles in a gas, as in a mist or smoke. The commonly used aerosol sprays contain an inert propellant liquefied under pressure. The pressure of the gas causes the mixture to be released as a fine spray (aerosol) or foam (aerogel) when a valve is opened.