Amalgam represents solution of some metal in mercury. In it there is a disintegration of parts of metal to an atomic state that cardinally changes chemical properties of the last.
Amalgam is a compound of metal with mercury. At the same time it is possible to see that depending on the nature of metal, ratios of components and temperature are formed three various groups of products: firm intermetallida (merkurida), liquid or firm homogeneous systems, liquid or firm heterogeneous systems.
Use of amalgams
The area use of amalgam is defined by metal which in it is dissolved. For example, amalgam of gold is excellent gilding therefore it is used for a covering gold of metal products, production of fluorescent, energy saving and induction lamps. Amalgams of alkaline metals show strong chemical activity therefore they found the application as reducers. The ores processed by mercury give almost all structure of rare-earth elements.
Properties
The most important property of amalgam is the possibility of receiving superpure metals. For this purpose mercury is driven away and as it has the smaller temperature of boiling, than base metal, there is an evaporation. One more important property of amalgam is change of chemical properties of the dissolved metals rather granting an opportunity to them completely them to show. In amalgam there is an atomization of the dissolved metal because of what the dense oxidic film preventing a surface from further oxidation is not formed. In such state metals are very active. For example, aluminum in usual conditions has very dense film of oxide which closes access to oxygen to more thickly metal, but in amalgam there is no it, and aluminum greedy connects to oxygen.
Receiving amalgams
The classical method of receiving amalgam consists in metal wetting by mercury, however in this case education of the last can be only on the metal which does not have an oxidic film, for example, gold. It instantly forms solution in mercury. Therefore use an electrochemical method more widely. In it on the mercury cathode there is a restoration of cations of metals to pure metal which instantly forms amalgam. The oxidic film can be removed by means of acid and then to process a surface mercury. Act concerning aluminum this way. There is one more interesting method which cornerstone the cementation process is. Give powder metal with smaller value of standard electrode potential to solution of salt of mercury. On a surface of a metal part there is a release of liquid mercury which enters interaction with the remained metal.