Brief update to note I'm still experimenting. I'm trying to extract tobacco flavor, to give vapor a more realistic taste. So far, I've got a refrigerator full of experimental liquid, all without much tobacco taste. How much nicotine is in there is anyone's guess.
Yesterday, after reading still more about extracting flavors, I added a lot of salt to the cooking water covering a small pile of pipe tobacco. Salt is said to be a kind of catalyst for increasing the extraction of a desired flavor. And, actually, I think this new batch is an improvement (I say 'think' because I haven't had enough of a trial to form a firm conclusion).
I put the final mix in an 8ml amber bottle with an eyedropper. The homebrew tobacco liquid was about 2ml. I added 4ml of vegetable glycerine. Then topped it with 2ml of Kahlua liquor to get some alcohol in the mix. Pretty good stuff. Adequate vapor, as usual. But not enough taste yet. When I get my Bickford's Kahlua, I'll use that instead of the glycerine and alcohol, and see how that tastes.
I also tried making a batch by covering the tobacco with just glycerine, and cooking it in that. Didn't work for me. The glycerine is syrupy and instead of nicotine moving to the glycerine, the tobacco just absorbed the gooey liquid and didn't give it back. I now have a pile of wet tobacco drying on my porch table! I did pour some Kahlua liquor over the tobacco, but it evaporated quickly in the heat of cooking. This was a total failure -- and I ended up spilling the wet tobacco all over the kitchen counter. Rachael Ray, I ain't.