We prepare solution of Nitric Acid ( HNO3) 33% with concentration
of 24Bums( density = 1.2) whichused to paration silver(Ag) from
Gold(Au) as mention In ISO11426, Also we used water( PH=7.4) but
after 5minute -1 days we found the concentration of solution( HNO3)
higher than before around 34Bums( 46%)
Well, let's be clear, nitric acid doesn't form spontaneously out of
the air, so on the basis of the little you've given, you
have not got more HNO3 there than you started with.
So, what's going on? I can think of two possibilities:
Maybe when you measured it initially the liquid was hot, and the
next time it was cold. The change in temperature would lead to an
increase in concentration, but a smaller volume. However, this
doesn't sound very plausible, as it wouldn't give the size of change
that you mention.
Hate to say this, but, maybe an error in your measurements? How
did you determine the concentrations? A variation in temperature
could well give large errors if you are measuring density as a means
of estimating concentration. Also note that if you use a pH meter
then these too are very sensitive to temperature, as well as needing
Pure water (a rather rare comodity chemically) has a pH (note, lower
case "p") of 7.0. Water with a pH of 7.4 is slightly alkaline, not
acid...... However, a few decimal points worth of variation either
side of neutral isn't going to make any difference at all in the
context of 33percent nitric acid.
It's an intriguing problem that we won't be able to solve without
more I suspect.
Now, I have to say this carefully, as I don't want to cause offence.
If I did then I wouldn't have taken the trouble to write the
comments above, OK? But, I am a bit puzzled by all this. You asked
some questions here almost exactly a year ago, which I did my best to
answer, both on and off list. But your further offlist questions and
indeed you initial enquiry, and this one too, don't sound exactly
like something that would be puzzling a "Head of precious metal
Laboratory". I wonder also about that "hotmail" address.......
Anyway, I've given you my thoughts on your current problem. No
doubt there are other approaches to it that I haven't thought of, and
others here will come up with those. No question is too stupid to
ask, provided it's a genuine enquiry. But I still wonder who you
Kevin (NW England, UK)