There are people who have mixed the two and claimed great results. Check out
www.photo.net and search the forums.

Adorama will ship it too. Freestyle will ship it ground with no hazmat
charge.

There is the original (pre-WW2) Rodinal formula, R09 at

http://www.jandcphotography.com/

Jorge

 B&H has had some sort of ongoing problem shipping even
slightly hazardous stuff. Try one of the other large mail
order places like Calumet or Freestyle. I don't know why
Rodinal should be any more hazardous than common liquid
drain cleaners, which are much more alkaline.

Yes, it does sound unlikely, but people have done it and they claim it
works. I cannot vouch for this myself, but here is one person's formula. A
google search might yield other information:

"Mixing Rodinal and Xtol by Sam Elkind

I read with interest the Nov 28th exchange on the BW Film Developing forum
about Vit C developers and the Rodinal variation.  On that forum, I have on
occasion mentioned a blend I use that gives excellent results with (at
least) Tri-X, Delta 100, Delta 400, and Verichrome, in both 135 and 120
formats. I think people have an initial reaction that the idea sounds
preposterous.

The blend uses both Xtol and Rodinal.  The origin for me was that Xtol
results were too flat, while Rodinal results were too grainy (no surprise).
A couple of years ago, I was searching for an ideal developer and after some
tests I settled on this blend. Following is the result of my testing
(quantities set to my 500 mL tank):

Xtol = 100 mL
water = 400 mL
Rodinal = 4 to 5 mL

Times @ 24 degrees C. are:
Tri-X (200) = 9 minutes.
Delta 100 = 10.5 minutes.
Verichrome = 8.5 minutes.

This blend may be useful to you and perhaps others.  I think you will find
the grain is quite acceptable, even in 35mm negs, and that tonality is
attractive, especially in highlights.  In the context of the exchange on the
BW forum, in which you made reference to Gainer's Rodinal variation, I
thought you might find this combo of interest."

Not always an acid and a base will react making a salt. Fairly common
mixes in developers are borax and boric acid; metabissulfite and
carbonate.
There will just be an equilibrium point. These non reacting mixes are
named buffers and highly regarded.
Xtol has ascorbic acid and borax.

Now, I wonder if just adding some alkali (carbonate? metaborate?) to
Xtol wouldn't be very much the same as adding a bit of Rodinal?
(I do not have any Rodinal to do a test).

Jorge

 That isn't quite how it works. Many developing agents
(reducing agents to be correct) are acid. Part of the alkali
in the developer is needed to neutralize them and some to
ionize them to make them active. In some cases the
developing agent _is_ coverted into a salt, which is the
active developer.
 Sodium Ascorbate is not the principle reducer in Xtol,
rather a form of Phenidone called Dimezone. Dimezone more
stable in solution than Phenidone. The ascorbate is also a
developing agent, with properties similar to Hydroquinone.
That is, it tends to develop high contrast images by itself
and is supperadditive to Phenidone and to Metol. It is this
last quality which is the important one in Xtol.
Phenidone-Ascorbic acid developers have properties similar
to Metol-Hydroquinone ones. The advantage of P-A is that
both reducers are less toxic and have less environmental
impact when discarded. Phenidone developers also tend to
yield greater film speed than Metol in similar types of
developers.
 Xtol is a relatively low pH (around 8.2 by memory)
developer with reasonably high salt content to reduce
emulsion swelling. Swelling is not so much a problem with
modern films as with older ones because the emulsions are
much harder to begin with but it is still good practice to
avoid high pH where finest grain is desired. The grain can
be incresed by swelling because it allows individual
developing silver crystals to be attracted to each other
forming clumps in the emulsion. The individual silver
grains, even of quite coarse emulsions, are sub-microscopic.
What we see as grain is the "clumping" of these particals
either as the result of combination of particals at differnt
places in the thickness of the emulsion, or as the result of
physical clumping. There are other factors too but these are
the main ones. To be low grain developers are generally made
low activity and close to neutral pH. Grain is not
exclusively a result of any one thing but of a combination
of factors including the way the silver grains are formed
during development. Nonetheless, certain rules apply if one
wants to minimise it.
 Unfortunately, I don't know a good, not-too-advanced text,
currently in print on photoraphic chemistry.