In general, new glue won't adhere to older glue
That's why the recommendation to take them apart so you csn scrape off the old glue. You would rather not do that, so the next best option is to use a slow 2 part epoxy squirted or forced into the joints as far as possible. You can work the back frame separately from the front and leave the sides for last OR try to do them all at once. It is "scary" to take them all apart, but that's the best way to insure solid joints. I did that here:
http://www.woodworkingtalk.com/f9/what-chairs-these-39917/
That's why the recommendation to take them apart so you csn scrape off the old glue. You would rather not do that, so the next best option is to use a slow 2 part epoxy squirted or forced into the joints as far as possible. You can work the back frame separately from the front and leave the sides for last OR try to do them all at once. It is "scary" to take them all apart, but that's the best way to insure solid joints. I did that here:
http://www.woodworkingtalk.com/f9/what-chairs-these-39917/