Hi, everybody!
Glad to join this forum. Thanks to my friend Reinhold G. who sent me a link to this thread. In fact, I re-discovered salt as fixer, searching the internet for old photo processes, namely daguerreotypes. Before the discovery of thiosulfates (once called hyposulfites) by Sir Herschell, salt was used to fix the daguerreotypes in a warm and concentrated solution. But it became a myth and I just succeeded to put it working again by using a solution of at least 300g/liter and some temperature, 35ºC is OK, it will not damage your film and you may reach acceptables fixing times of 90 minutes, or more, depending on the film.
But, thanks God, there are better fixers than salt. Another alternative is Ammonia, yes, it works. And all other thiosulfates other than the well known Sodium and Ammonium Thiosulfates. Also Potassium, Calcium and Magnesium Thiosulfates will fix and quickly your films or papers. Many fertilizers are using these thiosulfates, so they will be cheap enough, I hope.
PS - I am the Henrique mentioned above by Reinhold!