Best thing to do is call in the pros. You would be surprised on just how much a ¾ hardwood floor can be sanded. It will look fine; just have the pros do it. Don’t make the mistake I did and try to scrape it off first because they will just come in and sand the cr*p out of it. Trust me on this one. If it has not been sanded a lot (and it sounds like you did not) it will be fine as the goop on top is only “skin” deep.

Not sure this will help you, but we are in the midst of refinishing floors in our 1920 house and discovered a black, glue, tar paper-like substance. After trying numberous adhesive removers we tried (and please don't laugh) plain water. And it worked.

We just poured a bit of water over a small area (3 x 3) and placed newspaper over it. Let the paper sit for about 20 minutes and the adhesive comes right up with a plastic scraper.

I am trying to save some money by doing it myself. I cannot believe the water tip!! It really works. It loosens up the glue on the black tar (which stinks up the house) but it comes right up. Thank you all.

Good thing the water worked. Also, a product called JASCO does an amazing job dissolving flooring adhesive. It is available in the flooring department at Home Despot. Very toxic, but it dissolves the adhesive like water on sugar or heat on butter.

sounds like the glue is an emulsion type.
water would'nt work on cutback. water will also work on linoleum paste which is brown color

I had this same problem and used vinegar. However there are some small black stainns from the glue in the wood grain that I could not sand off. I tried bleach and it does not seem to come out. Should I just go ahead and stain it?