Ceramic tile on slab - install over adhesive left from vinyl tiles?
That black adhesive is called 'cut-back' and you can tile over it. It is recommended that you scrape as much as possible, leaving only an almost translucent film. This cut-back probably also may contain asbestos, so don't make dust with it. There are many modified thinset mortars that work well over cut-back. It'll say so right on the bag.
Tile 4 You LLC Troy, MI
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