Sony Xperia User Manual page 324

Each time text is entered, the corresponding friend appears.
If a friend is not in a Hangout, a message appears. Tap
Hangouts Operations
Ending a Chat
In chat window,
Ending a Video Chat
In video chat window,
Disabling Chat History
In chat window,
Deleting Chat
In chat window,
9
Turn history off
Delete DELETE
INVITE to invite them to the Hangout.