We did this when I was a jeweler years ago and the process happens very quickly, it is literally minutes so I would assume that at worst they are looking a a 5 to 10 minute window to dissolve one medal. The real issue is that the gasses given off are lethal and if not done carefully in a very well ventilated location you can do serious harm to yourself and anyone nearby. They would have known this and been fine, but someone just reading the article and thinking, hey, I have gold and some acid laying around let's see what happens, could end up dead.

The gas given off is Nitric Oxide (which combines with Oxygen in the air to create Nitrogen Dioxide) and Chlorine and even a small dose can cause serious damage to your lungs if not be fatal.

Very interesting, thank you for the answer.

I love how diverse HN can be. From Ph.Ds in computer science to former jewelers, there seems to be a little bit of everything.

Follow up question: would the gas have stuck around until the Nazis arrived a while (hours or less?) later? Or would their ventilation have dispersed it enough?

I remember in the science classes I took in HS the ventilation hoods pretty much removed most of the fumes, but we also never worked with anything that was particularly... pungent? My last science class was probably 5 years ago, so that's my level of understanding.

Fume cupboards work pretty well. If you leave the fan running I think all the airflow is in and up the chimney. I presume Bohr would have used one.

(Just got side tracked reading about old style fume cupboards http://www.cf.ac.uk/estat/sustainability/initiatives/ )

I would imagine that anyone who just happens to have some nitric acid (or any strong acid of appreciable quantity and concentration) lying around would have the sense to at least Google the products of the reaction, if they didn't know offhand. Other than that, gold doesn't react with terribly much anyway, does it?

I think that line was written for dramatic purposes to indicate that he didn't know how long it would take for the Nazis to show up so he had to be as quick as possible. It doesn't necessarily imply that it didn't take him hours and hours. (But I've no idea what the answer to your question is.)

Though I don't know any more details about the events that took place, there are several ways of speeding up the process. As 23kt gold is quite soft, it would be a quite straightforward process to finely divide it and thereby increase the reaction surface area. Additionally, you could (gently!) heat the solution, though at the cost of a more copious amount of nasty fumes.

Theres only one way to find out - win a nobel prize and dissolve it.

Two ways - they are sometimes for sale.