Subject: Re: Nitric Acid
From: Frank Harrison <ramanlab@vt.edu>
Date: Jan 14 1997
Newsgroups: rec.pyrotechnics,sci.chem

chuckad@erols.com wrote:

> Can someone please help me, it is about the production of nitric acid 
> from sulphuric acid, and potassium nitrate. Can it be done without a 
> retort, because they are hard to find. If I put them together without 
> heating, would the reaction still occour?
> 
> Thanx to anyone who can assist.

A retort is not strictly necessary. The best thing to use is a pyrex
distillation rig with ground glass joints. The main thing is that you 
cannot use rubber, as the hot nitric acid vapor will eat it. 

I have made nitric acid using a pyrex boiling flask with a teflon stopper 
as the reaction vessel, and a 6' piece of .25" i.d. teflon tubing run into 
a separate flask sitting in an ice water bath as the condensor. I made the 
stopper by turning a piece of teflon rod down on a lathe. It might be possible 
to use rubber by wrapping it thoroughly in teflon plumbing tape to protect
it, but I have not tried this.  You will have to heat the mixture. You
MUST use an oil bath for this. The oil bath eliminates hot spots, and 
reduces the tendency to "bump". Vegetable oil is ok, and it's cheap.
Mineral oil is better. Don't try motor oil, it stinks like hell when you 
heat it. I tried this once using an electric hot plate without an oil
bath, and had a liter of boiling hot sulfuric acid/sodium nitrate slurry
shoot out of the flask in a single solid stream, right in front of my 
face, spray all over the ceiling, and drip down on my head. I was lucky 
not to be blinded or killed. You must also be able to control the heat 
precisely. I use a variac. If you don't have acess to a fume hood, you
can do this in front of a window with a fan. The vapors are intensly 
poisonous, and some of the oxides of nitrogen which are formed will not
be stopped by the condensor. 

Frank

Subject: Re: Nitric Acid
From: Frank Harrison <ramanlab@vt.edu>
Date: Jan 24 1997
Newsgroups: rec.pyrotechnics,sci.chem

wpenrose@interaccess.com (William R. Penrose) wrote:

> >>Can someone please help me, it is about the production of nitric acid 
> >>from sulphuric acid, and potassium nitrate. Can it be done without a 
> >>retort, because they are hard to find. If I put them together without 
> >>heating, would the reaction still occour?
>
> See my other post about acids.  A retort isn't needed, but you need
> some kind of distilling apparatus.
>
> Be careful how you add the KNO3.  You might get a lot of heating.  One
> way is to make a conc solution of NaNO3 (more soluble than K salt) and
> drip it in.  Just adding it in a lump could be dangerous.
> 
> The reaction will occur, but you need to heat to distil the nitric
> acid over.

When I did this reaction using concentrated sulfuric acid obtained by
boiling down battery acid and sodium nitrate from the local feed and
seed, I did not observe any undue heating when the components were 
initially mixed. It might behave differently with KNO3, though I
would tend to doubt it.  The nitrate was in form of "prills", little 
balls slightly smaller than BB's. The prills did not begin to dissolve
until after the mixture had been boiling for a good five  minutes. A 
more finely divided nitrate might behave differently. It took a fair
amount of time after the boiling started for the acid to start coming 
over, which tells me that you have to drive the reaction pretty hard
in order to get the nitric acid form in the first place. The first thing
you get is a bunch of dark brown vapor, but it turns clear once the acid 
starts distilling over. For the benefit of those who may have missed the
beginning of this thread, I want to stress again the importance of using
an oil bath to heat the distilling flask. This stuff tends to bump 
violently, to the extent that it can shatter the flask or spray the
the boiling acid/nitrate slurry all over the room. The temperature needs
to be brought up slowly, over the period of an hour, because there is a
substantial lag between the the temperature that the oil reaches and
the temperature in the flask. You don't want to overheat it, and it's
a good idea not to fill the distilling flask more than one third full
as the goo tends to foam up a lot. This really is a dangerous procedure, 
but with good equipment and a great deal of caution it can be performed 
sucessfully. I would also recommend only doing small batches, especially 
at first.

Frank