Originally posted by SunnyG. I bought a lot of 4 Vivitar 24mm f2
So you have 4 copies total? You could use one to donate a rear element if needed. I've not worked on this specific Vivitar lens, but I have torn into I think a similar age Series 1 28-105. To get into that lens, I had to start by unscrewing the rear mount. I was basically able to feel my way through by just removing the next piece down as I went deeper and deeper. So, get a nice clean work area where you can spread out and just go at it. I'm going to guess that you're going to find that element held in place by a part that's going to need a lens spanner. Here are some samples:
amazon.com: lens spanner?tag=pentaxforums-20&
Regarding fluids to clean lenses, as already mentioned, stay away from acetone. Most cleaners seem to have alcohol or ammonia in them. You can search for the MSDS sheets and get an idea of what's in them. Here's a search for them for Eclipse:
MSDS Eclipse lens cleaner at DuckDuckGo
Of note, on some of my newer Pentax lenses (believe it was the DFA 15-30), there is actually a card saying not to use cleaners with alcohol.
And this may be of use - from Lens Rentals on what they do:
Lens Rentals | Blog