I have been a laboratory technician for 35 years, but you can take my word
or not. Citric Acid is one of the major components in most soft drinks,
and is no more toxic than they are. Phosphoric Acid is also in a lot of
soft drinks, but can be corrosive at full strength.
If you use Ferric Chloride, and or Ferric Nitrate, Please do not etch
steel or spill it on your metal work surfaces. No matter how carefully you
are in cleaning up, it still remains, and acts like a cancer to anything
that contains Iron (Ferric or Ferrous). You can neutralize it with
Ammonium Hydroxide, (Household Ammonia), but some times the cure is worse
than the disease.
Another CAUTION: Bleach and Ammonia produces Phosgene which was used
during World War I as a poisonous gas. Don’t mix NO HOW.