Common Problems with Hg, Au, Si, Os and Na

Silicon (Si)

The following suggestions are advised when working with silicon:

• Si is a common contaminant. In addition to the obvious use of laboratory glassware, common sources of contamination include silicon oil/grease, plastics containing catalyst residue, and air particulates.
• Si^o is easily dissolved using an equal mixture of HF:HNO₃:H₂O. SiO₂ is readily soluble in either HF or NaOH. Regardless of the mode of dissolution, solutions should be stored in plastics known to contain no catalyst residues or that have been leached with dilute HF for 48 hours.
• Exercise caution when hearing solutions containing Si and HF. Si may be lost as the volatile H₂SiF₆ when heated. When water is present H₂SiF₆ will not form. If you wish to remove Si from the sample then add sulfuric acid and heat in a Pt crucible.
• Silicon dioxide is soluble in caustic media. When acidified it is stable at low ppm levels but will slowly polymerize and precipitate out of solution. Common preparations involve sodium carbonate fusions in Pt crucibles and dissolution of the fuseate with HCl - make sure the ppm level of Si upon dilution is low ppm and the solution is not allowed to sit for extender periods.
• HF (even low ppm levels of HF) containing samples should not be put through glass or quartz introduction systems when Si, B, Na, or Al are analytes of interest.

• Si elemental data

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