The Aqua regia (of the lat. Aqua regia, royal water) is a highly corrosive and fuming solution, yellow, formed by the mixture of nitric acid concentrated hydrochloric acid and concentrated usually in the ratio of one in three. It was called that way because it can dissolve those called royal, royal, or noble metals. It is used in etching and some analytical procedures. Royal water is not very stable, so it must be prepared before being used.
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- 1 Story
- 2 Properties
- 3 Composition
- 4 Balance with metals
- 5 Preparation modes
- 1 Agua Regia (1)
- 2 Agua Regia (2)
- 3 Royal Water (3)
- 4 Spirit of Nitro
- 6 External links
- 7 Sources
The hydrochloric acid was discovered around the year 800 by alquimistapersa Jabir ibn Hayyan (Geber) by mixing the salt with vitriol (sulfuric acid). Jabir’s invention, which managed to dissolve gold in aqua regia, contributed to the effort of the first alchemists in their search for the philosopher’s stone.When Germany invaded Denmark during World War II, the Hungarian chemist George de Hevesy dissolved the award medals Max von Laue and James Franck’s Nobel in aqua regia, to prevent the Nazis from stealing them. He placed this solution on a shelf in his laboratory at the Niels Bohr Institute . After the Second World WarHe returned to the laboratory and rushed the gold out of the mix. The gold was returned to the Royal Swedish Academy of Sciences and the Nobel Foundation presented new medals to von Laue and Franck. The technical need for a selective method to recover metals that are increasingly having technical applications (nanotechnology, catalysts, etc.) has found a solution by the least expected route: using organic solvents.
A team led by Wei Lin, from the Georgia Institute of Technology (USA), has discovered a series of solvent mixtures that manage to dissolve noble metals with high specificity rates under moderate conditions. The finding is published in Angewandte Chemie. The team of researchers accidentally discovered that gold dissolves when left in a mixture of thionyl chloride (SOCl 2 ) and pyridine (C 5 H 5 N, heterocyclic hexagonal structure). Subsequent experiments showed that other organic compounds, such as style = “mso-bidi-font-style: normal” N, N-dimethylformamide ((CH 3 ) 2-N-CHO, DMF), imidazole (C 3 H 4 N2 , heterocyclic pentagonal structure) or pyrazine (C 4 H 4 N 2, heterocyclic hexagonal structure), could achieve similar effects when mixed with thionyl chloride. In all cases, gold is recovered by calcination. Selective dissolution of noble metals is achieved by varying the recipe and reaction conditions. Thus, for example, a SOCl 2 / DMF mixture dissolves gold but not palladium or platinum.
Although the selectivity achieved is spectacular and would allow the use of these mixtures in the recycling of noble metals, in terms of efficiency / cost, organic aqua regia is not currently competitive with traditional aqua regia. It does offer, however, a safer alternative (in terms of occupational risk prevention) and applications beyond recycling could be found, such as the synthesis of noble metal nanostructures or the selective elimination of nano-coatings. However, organic royal water is still far from having an industrial use.
It is one of the few reagents that are capable of dissolving gold, platinum, and all other metals. It was called that way because it can dissolve those called royal, royal, or noble metals. It is used in etching and some analytical procedures. Agua regia is not very stable, so it must be prepared just before being used.
Although aqua regia dissolves these metals, none of its constituent acids can do it on its own. Nitric acid is a powerful oxidant, which can dissolve a tiny (practically undetectable) amount of gold, forming gold ions. Hydrochloric acid, meanwhile, provides chloride ions, which react with gold ions, removing the gold from the solution. This allows the gold to continue to oxidize, so the gold eventually dissolves.
Aqua regia is a powerful solvent due to the combined effect of H + , NO 3 -, and Cl- ions in solution. All three ions react with gold atoms, for example, to form water, nitric oxide, or nitrogen monoxide (NO) and the stable AuCl – 4 ion , which remains in solution.
Agua Regia: A mixture made up of three volumes of HCl and one of HNO 3 is called “Agua Regia” for attacking Gold and Platinum:
nitric is concentrated, the reaction is this:
this atomic chlorine reacts with Gold and Platinum .
Balance with metals
Although aqua regia dissolves these metals and shapes them in an indescribable way, none of their constituent acids can do it on their own. Nitric acid is a powerful oxidant, which can dissolve a tiny (practically undetectable) amount of gold, forming gold ions. Hydrochloric acid, on the other hand, provides chloride ions, which coordinate the gold ions, removing the gold from the solution. This allows the gold to continue to oxidize, so the gold eventually dissolves. The water regia is a powerful solvent due to the combined effect of the ions H + , NO 3 – , Cl- solution and (Oxidation favorese by complexing capacity ion Cl –2 ) . All three ions react with gold atoms, for example, to form water, nitric oxide, and the stable complex ionic tetrachloride (AuCl 4 – ), which remains in solution.
1Au (s) + 3HNO 3 (ac) + 4HCl (ac) ——> HAuCl 4 (ac) + 3H 2 O (l) + 3NO 2 (g) 2
Royal Water (1)
Its base is the Spirit of Nitro, or Aqua Fortis, which is made Regia by addition of purified Ammonia Salt, or common salt, as follows: Four ounces of purified and pulverized Ammonia Salt are put into a flask and Add a pound of canonical Aqua Fortis. Heat in a sand bath with mild heat to dissolve the Ammonia Salt. Work in an open, ventilated place with a fume hood as there is abundant gas evolution. reaction and allow to cool, storing the resulting liquid in a tightly closed bottle.
Royal Water (2)
Put in a retort half a pound of sea salt or Gema Salt powder. Add one pound of Nitro Spirit or Aqua Fortis and distill to dryness in a sand bath. Collect distillate and store in tightly closed bottle.
Royal Water (3)
Rubellus Petrinus: “A Great Alchemical Work”; links on this homepage) It is placed in a one liter pyrex glass bottle, 250 ml of Nitro Spirit to be heated to 30 ° C, on a controllable temperature electric grill and in a sand bath. Nitro spirit preheated to a ventilated place or to the fume hood so that the vapors freely go outside. Add little by little and stirring 60 g of Ammonia salt. The chemical reaction may not start immediately, but after it starts, it is uncontrollable, so the liquid should not occupy more than ¼ of the volume capacity of the balloon. After the chemical reaction and all the Ammonia Salt has just dissolved , the water will have a beautiful yellow color. Let it cool and store it in a bottle with a ground stopper.
(Rubellus Petrinus, “A Great Alchemical Work”; links on this homepage) To prepare it, it is necessary to distill in a good pyrex glass alembic, or better still ceramic, in a gas oven with controlled temperature and in a sand bath. mix two pounds of Vitriol from Mars or Venus and one pound of revived nitro, in fine powder. Start the distillation over low heat, to extract the phlegm, and then increase the temperature, until the Spirit of Nitro distills it. which is noted by the release of glittering chestnut-colored vapors that completely fill the cucurbit. a wooden spoon of hard mango.Repeat the same operation in order to obtain a liter of Nitro Spirit. Rectify it until obtaining a stronger spirit at more than 30o Baumé.