Nitrosamine-free-3-isothiazolones and process

A stabilized 3-isothiazolone composition substantially free of nitrosamine impurities or precursors thereof which comprises:

• (a) a biologically effective amount of 5-chloro-2-methyl-3-isothiazolone and, optionally, one or more other biologically active 3-isothiazolone(s) of the formula ##STR12## wherein R and R.sup.1 are independently selected from hydrogen, halogen or an alkyl group of 1 to 4 carbon atoms;
• Y is an alkyl group of 1 to 8 carbon atoms, a cycloalkyl group of 5 or 6 carbon atoms, an aralkyl group of up to 8 carbon atoms, or an aryl or substituted aryl group of 6 carbon atoms;
• (b) a ring-stabilizing amount of a soluble metal nitrate salt;
• and
• (c) sufficient water to dissolve (a) and (b);
• said composition containing less than 100 ppm of by-product compounds containing an amine moiety capable of being nitrosated or a nitrosamine compound derived therefrom per 150,000 parts of (a).