Flooring Tile - Ceramic tile over concrete slab

We have a house in Florida that we would like to tile. The carpet and old vinyl tile came up rather easily. The tile was 7" and about 40 years old. There is a thin layer of what must have been adhesive on the floor. It is slick, dark colored and thinly spread in most places. Most of the tile was loose under the carpet that was removed. It seems that this adhesive should be removed or roughed up for proper bonding of the ceramic tile. Please give advice on surface prep and proper bonding agent. First post. Great site. Thanks.

Sounds like you just removed VAT vinyl asbestos tile. Hope you used proper precautions.

Scrape off as much glue as you can with a 4" wall paper scraper.
Most tile setters will use latex modified thinset mortar to lay the tiles. Check with some local tile contractors for suggestions in your area.