Furthermore, another effective process is also present which comprises the dehalogenation-hydrogenation reaction of a trihalotrimercaptan compound represented by the following general formula (X) or a tetrahalotetramercaptan compound: ##STR14## wherein x is an integer of 0 or 1; y is an integer of 0 to 4; z is an integer of 0 to 4; u is an integer of 0 or 1; and v is an integer of 0 to 3; the rela