Subject: What was the density of the plasma 300k years afte

The current dogma is that at about 300,000 years after the Big Bang, the
universe had cooled enough that photons uncoupled from matter (hot plasma phase
changed into hot gas phase) and the universe became transparent.  The photons
left over are the current microwave background radiation.
My question is - has any calculation been made as to what the average density of
the universe was at that time?  Perhaps 1 gram/cubic meter or 5 atoms/cubic
meter...?  I am curious as to how "thick" the universe was then - dense or
fairly close to a good vacuum as it is now.
I would like to be able to tell my chemistry students.
Thank you.

Re: What was the density of the plasma 300k years afte