Sodium persulfate

• Sodium
• Feinätzkristall
• Μ - peroxo sodium bis ( trioxosulfat )
• Naps

Colorless crystals

Fixed

2.40 g · cm -3 ( 20 ° C)

Decomposition from 148 ° C

Well in water ( 545 g · l-1 at 20 ° C)

Risk

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Sodium (chemical formula Na2S2O8 ) is the sodium salt of peroxodisulphuric. Since there - especially in impure or moist state - tends to disintegrate under oxygen formation, the salt and its solutions must never be stored in tightly closed containers due to danger of bursting.

The persulfate ion contains oxygen in the unstable oxidation state of -1, so sodium acts as a very strong oxidizing agent. For the differentiation of potassium peroxomonosulfate is deposited slowly from Iodidlösungen iodine, manganese (II ) solutions are oxidized to manganese dioxide in the presence of catalytically active silver ions. Even to permanganate

Use

Sodium is dissolved in water used in printed circuit board technology for etching the copper layers of boards:

Instead of sodium persulfate and the corresponding ammonium salt may be used.

Compared with the conventional etching with iron ( III ) chloride solution has the advantage of less sodium undercut even at higher temperatures (not above 50 ° C, increased decay), and thus a more precise contour sharpness (hence the trade name Feinätzkristall ).

The solution must be disposed of as hazardous waste or copper are removed by reduction of steel wool from the solution after use due to the copper content.

Sodium persulfate is used as a water-soluble initiator for radical polymerization (for example emulsion polymerization).

Rarely it is used in pyrotechnics. By mixing magnesium powder with sodium persulfate, one obtains a so-called flash powder ( flash).