Place tongue in kettle; cover with cold water.
Bring to a boil; boil for 20 minutes.
Pour off water; cover with boiling water.
Boil for 1 hour longer or until tongue is tender.
Remove from liquid; reserve liquid.
Cool tongue; peel and slice, return to kettle.
Add salt, pepper, sugar and equal parts reserved liquid and vinegar.
Boil for 20 minutes longer; cool in vinegar mixture.