Re: ELEMENTRY acid query

You have 3 phenomenon:
1)
At a certain % HNO3 becomes so concentrate that its affinity for water doesnt
stand its higher volatility.
100% HNO3 boils around 80°C while H2O at 100°C so the problem is exactly the
same as with ethanol/water...
No simple way to concentrate by evaporation...only distillation will do (what
is concentration buy condensation of the fumes).
2)
Over 80°C HNO3 starts to decompose into NOx and H2O (thus decreasing the
amount) --> vaccum distillation is the best.
3)
HNO3/H2O display an azeotropic mix at 69% BW; so if no dehydratant is used in
the initial batch no concentrated HNO3 will be obtained since buy distillation
of  40% solution the fume is 69% and gets poorer; and from 90% solution the
fume is near 100% while the remaining fluid gets poorer to 69% where it starts
to boil as a pure compound.

PH Z

djbrmiller wrote:

> Heating concentrated nitric acid will produce more NO2 fumes than water
> vapors, resulting in a lower concentration of acid.  You can assay the acid
> using a simple acid-base titration.  Find and follow a documented and well
> established procedure - do not "wing it."
>
> "my_2¢" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
> > Please excuse this question; I realize this must seem elementary but I
> > am quite stymied and it entails a work related situation.
> >
> > Cleaning out a acid cupboard where I work there are several bottles of
> > technical grade HNO3 which would be approx 70% but there are others
> > which are marked as "Fuming" (current date). My question is does there
> > exist a simple method to determine the percentage of acid if no
> > specific gravity info is present (i.e. 1.43, 1.50. etc, etc) ?
> >
> > There are some other bottles that are student's from last semester
> > that have a variety of information dealing with temp...can HNO3 be
> > "cooked" to a higher percentage (exposed to heat, thus reducing the
> > water content? I was told that under no circumstances to get rid of
> > the higher percentage grades as they cost quite a bit more money. But
> > if they can be reduced, why pay for a higher percentage? I am quite
> > aware of the "kitchen" methodologies of extraction w/ methylene
> > chloride and destilation but I always wondered why a higher percentage
> > was simply not produced via evaporation?
> >
> >
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