Quote Originally Posted by c6h6o3
... as opposed to using ammonium thiosulfate based (i.e. acidic) fixers.
Ammonium thiosulfate fixers are not necessarily acidic - TF4 is a good, well-known example of an alkaline one.

If there are any doubts as to whether the result will be archival, it hinges on the prescence of ammonia: Some believe that sodium thiosulfate-based fixers cannot adequately fix some emulsions.