Gold received amalgirovaniem or leaching. When amalgirovanii Gold dissolves in mercury (Hg), forming an amalgam, which is when the content of Au over 15% is solid. From the resulting amalgam is distilled in the condensing mercury devices, leaving in the form of nodules of Au and Ag (silver). Cleaning the Au from the silver is discussed below.
Leach solution using sodium cyanide or potassium — NaCN or KCN (a concentrated solution in distilled water), in which Au is dissolved in the presence of oxygen (air blowing) with the formation of complex anion [Au (CN) 2] — conventionally-zolotokisly potassium: 4Au + 8CN-+ O2 + 2H2O = 4 [Au (CN) 2] — + 4OH-.
From the resulting solution is isolated gold metallic zinc (sawdust Zn) in a colloidal precipitate 2 [Au (CN) 2] — + Zn = [Zn (CN) 4] 2 — +2 Au. The precipitated gold is treated to separate him from the zinc with dilute sulfuric acid, washed and dried.
Further purification of the Au impurities (mainly from the silver) is treating it with hot concentrated sulfuric acid, H2SO4, or need electrolysis. Au is also readily soluble in «aqua regia» (a mixture of hydrochloric and nitric HNO3 HCl acid 1:4), forming a complex zolotohloristovodorodnuyu acid H [AuCl4], which crystallizes upon evaporation in the form of pale yellow needles of H [AuCl4] • 4H2O.
Au is also easy to dissolve in the «bleach water» and aerated, ie blown with air, cyanide solutions of alkali metals.
All the compounds Au easily decompose when heated with the release of metallic Au. Due to the softness of Au is used in alloys, usually with silver or copper. These alloys are used for electrical contacts. Working with Data reagents requires great care, since they are all deadly poisonous. The presence of Au in the radio components is determined by the passport details and the characteristic color of the coatings.
Silver get amalgirovaniem or leaching. Leaching silver is dissolved by the concentrated solution of potassium cyanide KCN or NaCN in distilled water. From this complex cyanide compounds K [Ag (CN) 2], Na [Ag (CN) 2], metallic silver is precipitated by passing through a solution of electric current ([Ag (CN) 2] — Ag + 2CN-), a dense metal-ceramic crystal layer on the the cathode.
Hydrochloric acid and dilute sulfuric acid on Ag do not work. Silver is easily soluble in nitric acid, HNO3, therefore, nitric acid is used in the separation of Ag on gold Au, which is not soluble in HNO3: Ag + 2HNO3 = AgNO3 + NO2 + H2O.
All the compounds under the action of reducing Ag (eg, formalin, gidrozina) can be easily restored with the release of metallic Ag. The process is similar to amalgirovaniya gold Au. A large amount of Ag used for electrical contacts and silver-zinc batteries.
Isolation of the same platinum gold. The dissolution of platinum in «aqua regia» turns geksohloroplatinovaya acid H2 [PtCl6], which upon evaporation of the solution stands out as a red-brown crystals of H2 [PtCl6] • 6H2O, which on further heating decompose with the release of Pt