I'm planning on installing new ceramic tile on the slab floor in my dining room. After removing a couple of layers of carpet and disintegrated padding, the only thing left is a thin coating of black tile adhesive from a previous tile job. (I'm taking into account the possibility of the presence of asbestos.) This stuff appears to be petroleum based.
Do I have to scrape this adhesive up before mortaring in my new tile? If so, what should I be using to ensure the concrete is clean enough to get the new tile to adhere?

The black adhesive is probably an emulsion adhesive which is petroleum based.

Would not try to remove, very sloppy and it is a penetrating adhesive.

Scrape off loose adhesive and u should be good to go. Use thin set to set ceramic tile.

Good luck

Chuck