Nitric acid concentration

[mjgraham]

Hi,
Today I just distilled my first batch of nitric acid and that went well, I was wondering if someone had some formulas for determining it's concentration using copper? I don't have any thing to properly do a titration on it (no pH indicator). I was wondering if say 10ml removed 1g of copper then have a rough idea. I guess temp. affects it to .. humm... I guess I could do volumetric measurement I have a 10ml vol. flask.
Thanks

 

[butcher]

Try measuring the density.

 

[mjgraham]

Yea I had that thought about mid flight through the post, will do.

 

[mjgraham]

OK that worked , what I did was put the first 50ml and the second 50ml in different beakers when I was making it. The first 50ml gave me 1.2501 kg/L @ 22C or around 40% and the second 50ml was 1.3009 kg/L or around 48%. Not to bad for a first run. I didn't think the hotplate was getting hot enough did have everything covered but that is OK. What got me wondering the first batch came off clear/slight yellow(barely) the second 50ml was a lot more yellow. After sitting all night the first batch is still the same color the second batch is water clear. They were just covered with a watch glass is about it. I used this site to calculate it.
http://www.handymath.com/cgi-bin/nitrictble2.cgi

 

[mjgraham]

OK, one more question, Today I thought I would try a titration on my nitric just to see, I never thought that I had a jar of phenol red for the pool test. Any way here is what I did and I am not sure if I am thinking right. I made a 1M NaOH solution from 100ml H2O and 4g of NaOH. Put 100ml of H2O in a flask and 1mL of HNO3 in there along with 5 drops of the phenol red. I was able to add 13.6ml of the NaNO solution before it went pink and stayed. I was thinking I read it was a 1:1 for 1M NaOH to HNO3 so does that mean it was 13.6 M Nitric? if so I also measured the density it was 13.21g for 10ml so 1321g/L. If it is 13.6 M nitric does that mean 13.6 * 63g/mol -> (856.8g / 1321g)*100 = 64.8% ? What I am wondering about is when I calculate it with density only it is like 51.7%. I went back and searched a lot for titration on the forum, a lot of info but some of it gets me turned around.
Thanks


Edit. fixed spelling problems

 

[MysticColby]

were you mixing it while adding the nitric? is there any chance you over-shot how much was added?
is it important to distinguish between 51.7% and 64.8%? they're both fairly high
how accurate were your measurements for the density? (how much precision did your scale and cylinder have?) the difference between 50 and 50.2 ml might change the density enough to make it 64% (I know the density of those high percent nitric solutions are fairly close to each other). See if you can figure out a +/- on that density, then translate that to a range of percentages.

 

[mjgraham]

That is a good point, the flask is a 10ml flask with a 0.02ml tol. the scale on the other hand is a cheap scale that goes to milligram , it seems supprisingly close but I would say that is a main source of error. I did mix the nitric as I added the solution, the color transision was pretty quick at the point that I am assuming to be the end point. The only thing I can determine for sure if batch A is stronger that batch B of my nitric. I did the test before with some and it took 10.5ml to turn, put that on the hot plate at 90 C for an hour or two then retested and it was the 13.6 ml. I did not do a density test on the first one. from 50% to %70 is almost 1g in density for 10ml, I guess I need more volume to measure to lower some of this error.