I think the level of hazard depends on the concentration of the nitric acid and presence of impurities. The hazardous, thermally unstable intermediate is the acetyl nitrate CH₃COONO₂. It can be formed in small concentrations just by mixing the acids, but to form a hazardous and potentially detonable mixture there needs to be some dehydrating agent present (sulfuric acid, acetic anhydride) or at least low water conditions.

Concentrated fuming nitric acid is made by distillation from sulfuric acid solution and often contains sulfuric acid as an impurity. Glacial acetic acid can contain acetic anhydride as an impurity as well.

For more info google “nitration in acetic acid”.

Speaking only for myself etc. etc.

Slawomir Janicki

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