Nitric acid metal dissolution

A solution of hexachloroplatinic(IV) acid, H2PtCl6, is prepared by dissolving 4.5 g. f of platinum metal in 50-100 ml. of a 1 1 mixture of concentrated hydrochloric and nitric acids. The dissolution is carried out in a two-necked, round-bottomed, 250-ml. Pyrex flask equipped with a reflux condenser. The aqua regia solution is evaporated almost to dryness four times with successive 50-ml. portions of concentrated hydrochloric acid. 

If the alternative potassium hydroxide method is employed for the separation of Groups IIA and IIB, the KOH extract may contain As, Sb, Sn, Se, Te, and part of the Mo the residue may contain, in addition to HgS, PbS, Bi2S3, CuS, CdS, and PdS, the gold and platinum partly as sulphides and possibly partly in the form of the free metals. Mo is readily identified by the potassium xanthate or a-benzoin oxime test. The Au and Pt will accompany HgS after extraction with dilute nitric acid upon dissolution in aqua regia, Pt may be identified as the dimethylglyoxime complex in the presence of m hydrochloric acid after the Pb, Bi, Cu, and Cd have been removed. 

As in any strongly conductive medium, aluminium is prone to galvanic corrosion in contact with other metals (see Chapter B.3) such as stainless steel. Tests have shown that in boiling nitric acid, the dissolution rate of aluminium is multiplied by five while that of stainless steel is divided by two. 

Other Salts. Indium nitrate trihydrate [13770-61 -1], In(N02)3 3H20, is a soluble salt prepared by dissolution of the metal or oxide in nitric acid. Indium phosphate [14693-82-4], InPO, is precipitated by adding phosphate ions to a solution of an indium salt. It is soluble in water. 

The metal dissolves readily in concentrated HCl, H PO, HI, or HCIO. Nitric acid (qv) forms a protective oxide skin on the metal and can be removed by ca 0.05 Af HF. Dissolution of Pu metal in HNO —HF mixtures is common practice in scrap-recovery plants. The metal does not dissolve readily in H2SO4 because passivation of the metal surface occurs. The reaction of water and Pu metal is slow compared to that in HCl, HI, or HCIO. ... 

Etch Mechanisms. Most wet etches for the compound semiconductors employ oxidation of the semiconductor followed by dissolution of the oxide. For this reason, many wet etches contain the oxidant hydrogen peroxide, although nitric acid can also be used. One advantage of wet etching over dry is the absence of subsurface damage that is common with dry etching. Metal contacts placed on wet-etched surfaces exhibit more ideal characteristics than dry-etched surfaces. 

Chemical analysis methods maybe used for assay of silver alloys containing no interfering base metals. Nitric acid dissolution of the silver and precipitation as AgCl, or the Gay-Lussac-VoUiard titration methods are used iaterchangeably for the higher concentrations of silver. These procedures have been described (4). 

Most mineral acids react vigorously with thorium metal. Aqueous HCl attacks thorium metal, but dissolution is not complete. From 12 to 25% of the metal typically remains undissolved. A small amount of fluoride or fluorosiUcate is often used to assist in complete dissolution. Nitric acid passivates the surface of thorium metal, but small amounts of fluoride or fluorosiUcate assists in complete dissolution. Dilute HF, HNO, or H2SO4, or concentrated HCIO4 and H PO, slowly dissolve thorium metal, accompanied by constant hydrogen gas evolution. Thorium metal does not dissolve in alkaline hydroxide solutions. 

Cobalt(II) nitrate hexahydrate [10026-22-9], Co(N02)2 6H20, is a dark reddish to reddish brown, monoclinic crystalline material containing about 20% cobalt. It has a high solubiUty in water and solutions containing 14 or 15% cobalt are commonly used in commerce. Cobalt nitrate can be prepared by dissolution of the simple oxide or carbonate in nitric acid, but more often it is produced by direct oxidation of the metal with nitric acid. Dissolution of cobalt(III) and mixed valence oxides in nitric acid occurs in the presence of formic acid (5). The ttihydrate forms at 55°C from a melt of the hexahydrate. The nitrate is used in electronics as an additive in nickel—ca dmium batteries (qv), in ceramics (qv), and in the production of vitamin B 2 [68-19-9] (see Vitamins, VITAMIN B22)-... 

Cu(N03 )26H2 0, is produced by crystallization from solutions below the transition poiat of 26.4°C. A basic copper nitrate [12158-75-7] Cu2(N02)(0H)2, rather than the anhydrous product is produced on dehydration of the hydrated salts. The most common commercial forms for copper nitrate ate the ttihydtate and solutions containing about 14% copper. Copper nitrate can be prepared by dissolution of the carbonate, hydroxide, or oxides ia nitric acid. Nitric acid vigorously attacks copper metal to give the nitrate and evolution of nitrogen oxides. 

In some cases, a small amount of nitric acid, HN03, or hydrogen peroxide, H202, is added to the solution in order to accelerate the dissolution of the metal. Heating the solution increases dissolution rates as well. Taking into... 

An initial solution was prepared by dissolving metallic niobium powder in 40% hydrofluoric acid. The dissolution was performed at elevated temperature with the addition of a small amount of nitric acid, HN03, to accelerate the process. The completeness of niobium oxidation was verified by UV absorption spectroscopy [21]. The prepared solution was evaporated to obtain a small amount of precipitate, which was separated from the solution by filtration. A saturated solution, containing Nb - 7.01 mol/1, HF - 42.63 mol/1, and corresponding to a molar ratio F Nb = 6.08, was prepared by the above method. The density of the solution at ambient temperature was p = 2.0 g/cc. Concentrations needed for the measurements were obtained by diluting the saturated solution with water or hydrofluoric acid. 

The method can be applied to the determination of phosphorus in a wide variety of materials, e.g. phosphate rock, phosphatic fertilisers and metals, and is suitable for use in conjunction with the oxygen-flask procedure (Section 3.31). In all cases it is essential to ensure that the material is so treated that the phosphorus is converted to orthophosphate this may usually be done by dissolution in an oxidising medium such as concentrated nitric acid or in 60 per cent perchloric acid. 

An overview is presented of plutonium process chemistry at Rocky Flats and of research in progress to improve plutonium processing operations or to develop new processes. Both pyrochemical and aqueous methods are used to process plutonium metal scrap, oxide, and other residues. The pyrochemical processes currently in production include electrorefining, fluorination, hydriding, molten salt extraction, calcination, and reduction operations. Aqueous processing and waste treatment methods involve nitric acid dissolution, ion exchange, solvent extraction, and precipitation techniques. 

Dissolution. Plutonium is solubilized in nitric acid solutions at Rocky Flats. The feed material consists of oxide, metal and glass, dissolution heels, incinerator ash and sand, slag, and crucible from reduction operations. The residues are contacted with 12M HNO3 containing CaF2 or HF to hasten dissolution. Following dissolution, aluminum nitrate is added to these solutions to complex the excess fluoride ion. 

Under the effect of oxidizing agents, a metal may become passivated even when not anodically polarized by an external power source. In this case, passivation is evident from the drastic decrease in the rate of spontaneous dissolution of the metal in the solution. The best known example is that of iron passivation in concentrated nitric acid, which had been described by M. V. Lomonosov as early as 1750. Passivation of the metal comes about under the effect of the oxidizing agent s positive redox potentiaf. 

Iodine is also given off to a small extent in dissolving the uranium metal in nitric acid, but larger amounts may be obtained on steam distillation after dissolution (5). Ruthenium is often removed from the fission products by distillation of the volatile tetroxide formed by oxidation with potassium permangate, sodium bismuthate, periodic acid (38) etc. The distillation goes readily and gives a product of good purity. 

Fig. 11-14. (a) Corrosion rate of metallic iron in nitric acid solution as a function of concentration of nitric add and (b) schematic polarization curves for mixed electrode reaction of a corroding iron in nitric add W p, = iron corrosion rate CHNO3 = concentration of nitric add t" (t ) = current of anodic iron dissolution (cathodic nitric add reduction) dashed curve 1= cathodic current of reduction of nitric add in dilute solution dashed ciuve 2 s cathodic current of reduction of nitric add in concentrated solution. [From Tomashov, 1966 for (a).]... 

Elemental composition Cr 32.84%, Cl 67.16%. Chromium(HI) chloride may be solubilized in water by a reducing agent and the aqueous solution may be analyzed for chromium by AA, ICP, or other instrumental techniques. Alternatively, the compound may be digested with nitric acid, brought into aqueous phase, diluted appropriately, and analyzed for the metal as above. The aqueous solution (when a nonchloride reducing agent is used for dissolution of the anhydrous compound in water) may be analyzed for chloride ion by ion chromatography or chloride-selective electrode. The water-soluble hexahydrate may be measured in its aqueous solution as described above. 

Silicon reacts with strong bases forming silicates and hberating hydrogen. Sihcon is attacked by hydrofluoric acid if there is no oxide layer over it. Flowever, since the metal has a very thin oxide film over its surface, a mixture of nitric and hydrofluoric acid is effective in dissolution of the metal. While nitric acid dissolves the oxide layer, the metal is then attacked by hydrofluoric acid. 

Indium nitrate can be prepared from InCl3 and N205 158,159 the dissolution of indium metal in cone, nitric acid yields In(N03) xH20 (x = 3, 4, 5),7 which has been used as the source of cationic and anionic complexes.64 Salts of [In(N03)4] have been reported,64160 and Raman studies161,162 have demonstrated the presence of In/NOj complexes in solution the stability constant results have been reviewed.9... 

Uranium-Zirconium Alloy Explosions. An inter-metallic compd, UZr3 (mw 511.69), exists in which a-U and a-Zr have limited solid solubility. According to the ref, this solid soln is designated as the epsilon phase, and has approx lower and upper limits of 41 to 53 wt % Zr. Hence, lesser or greater fractions of finely divided epsilon phase exist in a matrix of a-U. On treatment with nitric acid for the purposes of etching, dissolution or pickling of the U-Zr alloy, the a-U... 

The sulfato and nitrato triphenylphosphine complexes were also obtained by the reaction of sulfuric or nitric acid with [Pd(PPh3)4] in ethanol.132 Nitrato complexes can also be prepared by isolation of [Pd(N03)2(H20)2], obtained by dissolution of Pd metal in concentrated nitric acid,133,134 and subsequent reaction with ligands L (e.g. L2 = 2,2 -bipyridyl).135 A crystal structure determination has been carried out for the complex cis-[Pd(N03)2(DM50)2].136... 

During the dissolution of the irradiated fuel in nitric acid the acidity of the solution will fall from 7-8 M HN03 to 3-5 M HN03. The metals present will be dissolved as their nitrate salts and under these conditions the Group I and II metals, principally cesium, strontium and barium, will then be present as solvated mono- or di-cations respectively. These do not form extractable... 

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