Formula Na2S2O8 Density 2.4 g/cm³ Appearance white powder | Molar mass 238.03 g/mol Melting point 180 °C | |
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Etching a printed circuit board pcb using sodium persulfate
Sodium persulfate is the inorganic compound with the formula Na2S2O8. It is the sodium salt of persulfate (also called peroxydisulfate), an oxidizer. It is a white solid that dissolves in water. It is almost non-hygroscopic and has good shelf-life.
Contents
Production
The salt is prepared by the electrolytic oxidation of sodium hydrogen sulfate:
2 NaHSO4 → Na2S2O8 + H2Oxidation is conducted at a platinum anode. In this way about 165,000 tons were produced in 2005.
The standard redox potential of sodium persulfate into hydrogen sulfate is 2.1 V, which is higher than that of hydrogen peroxide (1.8 V) but lower than ozone (2.2 V). The sulfate radical formed in situ has a standard electrode potential of 2.7 V.
Applications
It is mainly used as a radical initiator for emulsion polymerization reactions for styrene based polymers such as Acrylonitrile butadiene styrene. Also applicable for accelerated curing of low formaldehyde adhesives.
Other uses
It is a bleach, both standalone (particularly in hair cosmetics) and as a detergent component. It is a replacement for ammonium persulfate in etching mixtures for zinc and printed circuit boards, and is used for pickling of copper and some other metals.
It is also used as a soil conditioner and soil remediation and in manufacture of dyestuffs, modification of starch, bleach activator, desizing agent for oxidative desizing, etc.
Organic chemistry
Sodium persulfate is a specialized oxidizing agent in chemistry, classically in the Elbs persulfate oxidation and the Boyland–Sims oxidation reactions. It is also used in radical reactions; for example in a synthesis of diapocynin from apocynin where iron(II) sulfate is the radical initiator.
Safety
The salt is an oxidizer and forms combustable mixtures with organic materials such as paper.