Russ’s story emphasizes the important take-home lesson about chemical compatibility that I often argue with school administrators (occasionally science teachers, but most of them trust me on this).  Yes, we know that chemicals will not jump from one closed bottle to another closed bottle..  The issue is what impurities might be lurking around.  If the acid cabinet has a dedicated HNO₃ compartment (usually polypropylene:  I tell administrators it’s like a big Tupperware container), generally, nitric acid is the only thing that would ever be stored in that (used properly, of course).  The wooden acid cabinets (ours usually have a plastic liner) contain a variety of acids, plus whatever “crud” might have been on the table top where the bottle was last set.

 

So, my usual message of doom and gloom is this:  if you want the “high risk” chemicals, be prepared to store them correctly or find a different way to do the lesson.  What I tell school administrators is that if the MSDS (soon, the SDS) says “store in a dedicated cabinet,” and this direction hasn’t been followed, the school will most likely be responsible for any damages that result from an accident, regardless of the circumstances.  In the K-12 world, unfortunately every tragic lab accident seems to be preceded by the phrase, “well, it worked hundreds of times before this!  I can’t imagine what happened!”

 

 

 

Russ – I can provide a real life nitric acid/ wood fire story, but it involves sawdust, not wooden shelving. Years ago, when a variety of different absorbents were used for  labpacks, an east coast transporter packed some chemicals in New England before driving the load to their TSDF in New Jersey. The driver decided to stop at his mother’s house on the way to have lunch. After a few minutes inside, a neighbor knocked on the door to tell him his truck was on fire. It turned out that some concentrated nitric acid was packed in sawdust. It is unknown if residuals on the outside of the bottle were the cause or if perhaps the cap was cracked, but the forensics clearly indicated the incompatibility was the cause of the fire.

 

I agree with you, however, that acetic and nitric by themselves are unlikely to react.

 

Russ

 

 

 

Dear Learned Ones…

 

Several years ago when confronted with the assertion that we couldn’t store nitric acid and acetic acid together (or nitric acid n a wooden shelf) because they were incompatible I conducted an experiment.

1.    I took glacial acetic acid and added concentrated nitric acid while stirring, anticipating a reaction… nothing happened. It didn’t get hot, cold or have gas evolve

2.    So after reaching a 50:50 mix I began heating while stirring (did I mention this was in a hood with proper PPE and a written procedure way back in the early 1990’s)

3.    I got in boiling and still there was no obvious reaction.

 

4.    Now I added pencil shavings in small amounts in the belief it would catch on fire…

5.    Nothing apparent happened.

6.    So I added more.

 

7.    Finally after 20 minutes mild boiling with concentrated nitric, glacial acetic and wood pieces I squirted just a drop of acetone a definitely got the reaction I expected (flame)

 

Does anyone have a real world experience where nitric acid caused an unwanted reaction with acetic acid or a wooden shelf?

 

Sincerely,

-Russ