Non-cyanide acidic silver electroplating bath and additive therefore

An aqueous non-cyanide acidic silver electoplating bath, which comprises a water soluble silver salt in a concentration of about 5 to 50 grams of silver per liter of solution, sodium thiosulfate present in an amount of about two moles of thiosulfate for each mole of silver in said silver salt, a bisulphite buffer in the form of sodium bisulphite present in an amount of about 4 grams per liter to saturation, and a sulfate in the form of an alkaline metal sulfate present in an amount of about 4 grams per liter to saturation, said solution having a pH of about 3.5 to 7.0, said solution further including a brightener system which comprises at least one anionic sulfonic acid derivative surfactant, at least one amphoteric nitrogen containing carboxylic or sulfonic derivative surfactant, at least one cationic or non-ionic surfactant, at least one solution stable soluble aldehyde, and at least one C=S containing compound or tautomer thereof.