black phelgm is usal for those who smoke.
Phelgm discharge
Phlegm.
Nothing happens
you die
pain
You Die
you die...
You can get chemical burns along your throat and stomach if you swallow lye.
You burp bubbles
It depends on how much you swallow. If it is a large amount, you could get diarrhea and/or vomit.
This too will pass.