Sodium (Na) does not occur native. Metallic ( Металлический ) sodium is produced by the decomposition of a melt of sodium chloride by an electric current ( электрический ток ) . Sodium is a soft silver white metal ( металл ) , tarnishing easily in air. It decomposes in water, forming sodium hydroxide ( гидроксид натрия ) and hydrogen ( водород ) . It is used in heat-exchange systems .
Sodium forms 2.8% of the Earth's crust ( Земной коры ) . It is a constituent of many very important rock-forming silicates, notably of albite ( альбит ) , NaSlsbOg, the sodic end-member of the plagioclase feldspars ( полевые шпаты плагиоклаза ) . A less common feldspar, anorthoclase ( прерванный ) , (Na,K)AISi 3 0 g, crystallizes from sodium-rich magmas, as do sodium-pyroxenes ( пироксены ) , sodium-amphiboles ( амфиболы ) and the feldspathoids ( фельдшпатоиды ) , nephe-line, sodalite ( содалит ) and hauyne. Scapolite ( Скаполит ) , and paragonite ( парагонит ) the sodium-mica, are other sodium-bearing silicates. Amongst the important group of silicates known as the zeolites ( цеолиты ) , sodium-bearing types are represented by heulan-dite, analcime, natrolite ( натролит ) , stilbite ( стильбит ) etc.
The non-silicate ( несиликатный ) sodium minerals mostly occur as saline residues deposited by the evaporation ( испарение ) of enclosed bodies of salt water. Sodium chloride, NaCl, is the compound of the most frequent occurrence in nature, and is procured for industrial purposes either as rock salt ( каменная соль ) or by the evaporation of sea water ( морская вода ) . NaCI is used mainly for the production of chlorine ( хлор ) . Sodium production is given in terms of the amount of soda-ash ( кальцинированной соды ) (hydrous sodium carbonate) produced. In 1985 the total amount of soda-ash produced was 29.3 Mt, of which 9.4 Mt was produced by the USSR and the Eastern bloc, 8.16 Mt by the USA, and 6.25 Mt by Western Europe. Compared with the vast supplies of salt, other sodium compounds are relatively insignificant, though there are important deposits of the carbonate, sulphate and nitrate ( нитрат ) .
Tests. Sodium salts colour the blowpipe flame intense yellow ( желтый ) . After heating before the blowpipe, sodium compounds give an alkaline ( щелочной ) reaction with litmus; this reaction is, however, also given by salts of the other alkalis ( щелочи ) and of the alkaline earths ( щелочноземельные земли ) .
The sodium minerals, other than silicates, dealt with are:
chloride rock-salt, halite, NaCl
sulphates thenardite, Na2SO4
mirabilite, Na2SO4.10H2O
glauberite, Na2Ca(SO4)2
carbonates thermonatrite, Na2CO3.H2O
natron, Na2CO3.10H2O
trona, Na3H(C03)2.H2O
gaylussite, Na2Ca(CO3)2.5H2O
To these may be added:
borates borax, Na2B4O7.10H2O
ulexite, NaCaB5O9.8H2O
fluoride cryolite, Na3AlF6
No comments:
Post a Comment