Gmail autosaves your chats in Gtalk under chats section.If you want to disable this feature for the sake of privacy and as a precaution in case your account gets hacked,these are the things you need to do.
1.Sign in to your gmail account. 2.Go to settings. 3.Click on the 'chat' tab 4.Check on . 5.Click on 'Save Changes' and you are done.