Bob, exactly.
I have to dissect the sucker step by step. The initial extraction of 10 grams of tobacco (theoretically there will be around 200 mg of alkaloids available) requires 150 mL of solvent to get back 110 mL of solvent, so immediately, we're losing a bit more than a quarter of the available alkaloids. I asked myself if using 200 mL of solvent would help. If I did this, I'd get back 160 mL of the 200 used, so I'd improve from losing 27% of the available alkaloids to losing 20% of the available alkaloids. Considering the high price of the solvent, this was not worth the additional solvent cost.
This is the sort of stuff I have to work out. In the end, it gave me a table for the extraction of 10 grams of well-ground NAS Organic tobacco:
50 mL solvent: 80% loss (40 mg alkaloids/200 mg recovered)
100 mL solvent: 40% loss (120 mg alkaloids/200 mg recovered)
150 mL solvent: 27% loss (146 mg alkaloids/200 mg recovered)
200 mL solvent: 20% loss (160 mg alkaloids/200 mg recovered)
250 mL solvent: 16% loss (168 mg alkaloids/200 mg recovered)
Considering the high solvent cost, I figured the point of diminishing returns was around 150 mL. The really surprising thing I found was that these numbers represent simply draining the solvent from the tobacco. Additional heroics like trying to squeeze out the tobacco to get more solvent only yield 5 - 6 mL extra, while forcing gunk out that makes life harder later on in the procedure.
I then had to rethink the table. What if I added 40 mL of solvent after all the solvent that could initially be gotten out was recovered. Since I know that 10 grams of the organic NAS will hold onto 40 mL of solvent, this additional solvent addition to the tobacco would allow me to recover half of what was left behind in the tobacco. Now the table looks like this:
50 mL + 40 mL solvent: 40% loss (120 mg alkaloids/200 mg recovered)
100 mL + 40 mL solvent: 20% loss (160 mg alkaloids/200 mg recovered)
150 mL + 40 mL solvent: 13% loss (174 mg alkaloids/200 mg recovered)
200 mL + 40 mL solvent: 10% loss (180 mg alkaloids/200 mg recovered)
250 mL + 40 mL solvent: 8% loss (194 mg alkaloids/200 mg recovered)
In this case, the extra volume is worth using, and with multiple solvent additions, a total of 190 mL of solvent achieves better recovery than a single addition at 250 mL. Multiple extractions generally do this for you, but you've gotta run the numbers and consider material costs at the same time to see if it's worth the effort or not.
Lately I've been dealing with the emulsion that forms during the preliminary cleanup of the initial tobacco extract.
When I'm working with this issue, I typically inspect it, and do any of a number of things to overcome the emulsion... each of which is tucked away in my "bag of tricks" gathered over many years.
When I consider what I'd tell someone else to do about it, I find that I can't, there's just too much experience that can't be simply described. So, I simply have to use a pretty rigorous "salting out" procedure, test that it works for the materials being used, and then describe how to do it.
This is why I've so far put 40 grams of NAS Organic tobacco to the task. Every time I come across something that could cause someone a problem, I have to come up with a sure-fire solution. So far, I'm on round 4, and every time I guess wrong about what action to take, I have to start over since I can't undo my dead-ends.
Even when I finally get it all worked out, more than a few will take one look at the procedure, and say, "I'll stick with the snus".
. Just got some 02 from getsnus and I like it about as well. It's a full size portion, but they made it a little longer and skinnier for a more comfy fit in the cheek. Also less noticeable and it delivers mild tobacco flavor with a bit of a nutty undertone and 13 mg nic. A definite keeper. Haven't used the PV at all today, no desire to 
