3. Explain electrodeposition technoly of rhenium

Electrolytes for the deposition of rhenium contains potassium perrhenate having a solubility in 18 – 9.5 g/l, at 28, is 17.2 g/l in 90 – 95 g/l For the deposition of rhenium is most appropriate to apply the following electrolyte (g/l) and mode of deposition: the potassium perrhenate – 15; ammonium sulphate – 200; temperature – 70; the current density of 10-15 a/dm2; pH – 1; the current efficiency is 25-28 % Anodes platinum. The predetermined pH value is obtained by the surging of sulfuric acid. The deposition rate reaches 14-15 µm/h. Coatings are light grey, shiny look. Of electrolytes known and also ammonium sulphate. Composition (g/l) and mode of operation of the ammonia electrolyte is the following: the potassium perrhenate – 1; citric acid – 50 ammonia to pH=9.5 in; temperature - 70 the current density is 8 A/dm2; the current output – 2 % The composition of the sulfuric acid electrolyte and the mode of operation of the following: the potassium perrhenate – 15; sulfuric acid – 12-15 temperature - 85-90 C; pH of 0.9-1 the current density is 15 A/dm2; current output–15-19 % In this work the electrolyte the dense shiny coverage. Insoluble platinum anodes. The deposition of rhenium from the electrolyte with hydrofluoric acid is carried out in several variants. So, for one of the electrolytes of the following composition and mode of deposition: the ammonium perrhenate in terms of metal – 5 hydrofluoric acid – 25 temperature - 80 C the current density is 10 A/dm2 the current output – 40 % The deposition of lead with insoluble anodes and a light and crisp coating.

4. Explain electrodeposition technoly of platinium.

Of electrolytes proposed for patinirovanija, the most famous of phosphate and cis-diaminoethane. For preparation of phosphate electrolyte metallic platinum was dissolved in Aqua Regia. The resulting chloride of platinum, crystallized in the form of yellow crystals is neutralized with ammonia and the resulting ammonium chloroplatinate used for making the electrolyte. For the deposition of coatings with thickness up to 200 µm ammonium electrolyte was developed, in which ammonium chloroplatinate goes into solution without additives ammonium phosphate. Is recommended for the following composition (g/l) and mode of deposition: chloroplatinate ammonium – 24;sodium phosphate – 130; temperature – 60; pH is 4.8; the current density of 0.4 – 0.5 A/dm2; the current efficiency – 75-85 % The electrolyte requires prior probrably the rate of up to 20 Ah/l, without which benign coatings can not be obtained, and the current output is excessively low. In addition, it is necessary to apply the electrolyte with compressed air and to prevent the fall of chloroplatinate concentration below 5 g/l in terms of metal. CIS-diaminoethane electrolytes are marked by the simplicity of their preparation. For this purpose, the metallic platinum was dissolved in Aqua Regia, as is done in obtaining the phosphate electrolyte. The resulting solution crystallized chloride of platinum. When mixing solutions of platinum chloride with a solution of sodium nitrite, taken in ten-fold excess against the estimated amounts, and heating the resulting mixture up to 40-50 With tetravalent to divalent platinum is recovered with the formation of potassium latinamerica. To the obtained solution poured calculated amount of ammonia to obtain cisisomer diaminetetra of platinum, which gradually falls as a voluminous crystalline mass. For electrolyte we recommend the following composition (g/l) and mode of deposition: diamonite platinum in terms of metal – 10

ammonium nitrate – 100-120 sodium nitrite – 10-12 ammonia 25% aqueous – 50-60 temperature is 98-100 C the current density of 8-9 A/dm2 Insoluble platinum anodes.

5. Explain electrodeposition technoly of paladium. Palladium is deposited on the copper or on silver. When deposited on other metals as the underlayer, it is necessary the coating of copper or silver. Of electrolytes, palladium received an application of phosphate, nitrite and aminofluorene. In the laboratory get H2PdCl4, palladium chloride, rolling after repeated evaporation with HCl to reddish-brown crystals PdCl2 X 2H2O. For its finely cut metallic palladium, placed it in a porcelain Cup, pour strong nitric acid and heated to boiling on a sand bath. Further additives are dissolving with Aqua Regia until the full transition metal in the salt solution. After evaporation of excess solution to slabovrajennoe crystalline state administered supplements of hydrochloric acid with a density of 1.19 g/cm3 and several times was evaporated almost to dryness. The obtained crystals of palladium chloride used for the further preparation of the electrolytes. Palladium chloride easy can also be obtained by anodic dissolution of metallic palladium in hydrochloric acid. The electrolyte is obtained by dilution of strong hydrochloric acid with water in a ratio of 1:1, and then halt the anodes of palladium and the metal is transferred into a solution of palladium chloride at a temperature of 15-25° C and anode current density of 5-10 A/dm2. Phosphate electrolyte with the following composition (g/l) and mode of deposition: PdCI2 palladium chloride.2H20...... 30 sodium phosphate Na2HPO4.12H2O.............. 100 ammonium phosphate (NH4)2HP04.12H20............. 50 Benzoic acid ....... 2,5 Temperature, °C .............. 70-80 The current density, A/dm2 ......... 0,7 pH..................... 6,5—7,0 The current yield %,.......... 90 The process is carried out using insoluble graphite or palladium anodes. The same electrolyte composition suitable for the bell bath. Coating with the thickness up to 10 µm are obtained dense and shiny. The adjustment of the electrolyte composition is produced mainly palladium chloride dissolved in a pre-selected dose of the electrolyte when heated. Nitrite electrolytes are characterized by the possibility of using soluble palladium anode. So, one of them suggested the following composition (g/l) and coating mode: Palladium chloride PdCl2.2H20...... 5-10 Sodium nitrite ...........15-20 Sodium chloride NaCl...........40-50 As anodes halt plates of palladium and graphite with the ratio of surfaces of 2:1. Coating thickness up to 2 microns are obtained shiny.