How to remove floor adhesive from concrete?
I have had to go through this a few times recently.  You can try hot water or some kind of remover but you may be making a liquid mess where you adhesive just spreads out. 

I have found the fastest way of dealing with it is chiseling for a small area or power scraping - rent one or I personally own one that hooks up to compressor - scraper was like $15 at big box.  Yes the work is more laborous but it gets done quicker and cleanup is with a broom.