R¹R²N—(C═S)—S—S—(CH₂)_n—S—S—(C═S)—NR¹R²  (I),

wherein the R¹ and R² radicals are each independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aralkyl, phenyl, substituted phenyl, alkylaryl, and a heterocyclic ring having 4 to 8 carbon atoms including at least one nitrogen atom, and where n is an integer from 2 to 8,

comprising the step of reacting a compound of the formula (II)

[R¹R²N—(C═S)—S]_zMe¹  (II)

wherein R¹ and R² radicals are each as defined in the formula (I) and z=1 when Me¹ is an alkali metal or ammonium ion and z=2 when Me¹ is an alkaline earth metal ion,

with the a compound of the formula (III)

Me²O₃SS—(CH₂)_n—SSO₃Me³  (III)

wherein Me² and Me³ are the same or different and are each monovalent metal ions or ammonium ions and n is as defined in the formula (I),

wherein said step of reacting is performed in the presence of water, a carbonyl containing compound and an organic solvent, in a pH range of 7 to 14 at a reaction temperature of 0° to 90° C., until the compound of the formula (I) reaches a percent yield of at least 80% based on the salts of the formula (III),

further wherein the amount of the compound of the formula (II) is 180 to 250 mol % based on the moles of the compound of the formula (III) used, the amount of the carbonyl containing compound is 5 to 600 mol % based on the moles of the compound of the formula (III) used, and the amount of the organic solvent is 2 to 100,000 parts by weight based on 100 parts by weight of the theoretical yield of the compound of the formula (I).