Fuse/heat for 40 minutes (Zr/Hf materials may take up to one hour depending upon the mesh of the sample and mixing with flux) and make certain that the sample is finely ground and well mixed with at least a 20:1 ratio of flux to sample. Sodium Carbonateįusion is done in a Pt crucible at 1050 ☌. This should give a clear solution containing the Zr and all other constituents of the ore. Next, the solution is made acid (excess of 10% or more) with HCl and boiled until carbon dioxide is expelled. The vessel is covered with a watch glass and the solution is boiled until the carbonate lining has dissolved. When cool (after fusion with the peroxide), the crucible is placed in a large Pt or porcelain dish and covered with warm water. This is a great technique for protecting the Ni and eliminating this very spectrally rich element from entering your sample solution, but it will take some practice to perfect the technique. Several grams of sodium peroxide are then melted in the crucible and allowed to solidify on the bottom after lining with the sodium carbonate to prevent particles of the ore from being caught in the carbonate lining and remain unfused. This technique involves lining the crucible with sodium carbonate by melting (1000 ☌)) and then swirling to line the walls while cooling. There is a technique for protecting the Ni crucible from attack by the peroxide. Peroxide fusions containing organic materials are done but can be very reactive to explosive. Exercise caution if organic material is present by performing a dry ash first. Use a Ni crucible and fuse for 5 to 10 minutes at a dull red heat over a small flame. The following are the most commonly used: Sodium Peroxideįusion of up to 0.5 grams of sample with 10 grams of sodium peroxide (mix well). The oxides are generally not soluble in acids. All but one very rare mineral contains more Zr than Hf (hafnon, HfSiO 4). The two most common zirconium-containing minerals are baddeleyite (ZrO 2) and zircon (ZrSiO 4). Alloys containing Zr + some combination of Ti, W, Nb, Ta, and Hf (0.5g) -5 mL HNO 3 + 5 mL HF + 15 mL 1:1 H 2SO 4.The metals are best dissolved in HF in combination with other acids such as nitric, perchloric and HCl. Zirconium is used in high temperature applications (furnace lining, crucible materials) but is not used extensively due to its high cost. Both metals are passivated by a protective oxide film, which makes them almost inert towards any chemical attack (exceptions are hydrofluoric acid and alkali melts containing fluoride that dissolve both elements). Differences in the solubility of the tetrachlorides in ethanol have been used for the separation of zirconium and hafnium. The tetrachloride is reduced to elemental zirconium in the presence of metallic magnesium. The ZrC (zirconium carbide) that's produced is reacted with chlorine to produce ZrCl 4. Heating zircon sand in the presence of graphite in an electric furnace forms the carbides. These metals resemble stainless steel in appearance with melting points of 18 ☌ respectively. Zirconium and hafnium metals, like titanium, are hard and resistant to corrosion. In materials where titanium is present in minor or trace amounts sampling and handling considerations relative to the sample matrix will apply.įor additional details, see the following information on sampling and subsampling. Safety considerations appropriate to the use of HF will apply. However, many analytical measurement techniques require a solution of the sample and HF is most often required. Materials containing Zirconium and Hafnium compounds are also relatively non-hazardous and do not present unique sampling and handling problems. Zirconium tetrachloride is not as reactive as the TiCl 4 where hydrolysis results in the formation of derivatives such as the oxychloride, ZrOCl 2, instead of the oxide as is the case with TiCl 4. Hf compounds are classified a factor of ten lower. The toxicity of Zr compounds is generally classified with a maximum working concentration (MAK) of 5 (mg m -3), and a threshold limit value/time weighted average of 5 (mg m -3). This is likely due to the very limited solubility of their compounds. No toxicity is known and no industrial health hazards are reported. The sampling and handling of Zr and Hf materials is not generally a problem because they are relatively inert and nontoxic.
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