NaOH Normality Calibration

NaOH Normality Calibration

Post by Joe Sallust » Mon, 25 Nov 2002 09:50:34



Is there a shelf life on the potassium acid phthalate?

I tried a little experiment today; I took 2.5 g of tartaric acid and
added distilleed water to 250 ml; that should have given me a 1%
solution expressed as tartaric.  I then titrated that against my
0.103N NaOH and needed 13.1 ml of NaOH to get to an end point of 8.2.
All of that works out pretty close, given the fact that I was not
using the best measuring practices; it was right in the ballpark.

My question is, why use potassium acid phthalate as a standard if this
works?  Was it dumb luck that the values came out close?

I had two open bottles of potassium acid phthalate indicate two
different values, that is the reason I was playing around with this.
(Both has small black deposits in them, I used the values from the one
with the least deposit.)  I am going to repeat the experiment with
more accurate measurements and a fresh bottle of potassium acid
phthalate.

Thoughts anyone?
Regards,
Joe

 
 
 

NaOH Normality Calibration

Post by Joe Sallust » Wed, 27 Nov 2002 19:35:16


Thoughts,anyone?
Quote:

> Is there a shelf life on the potassium acid phthalate?

> I tried a little experiment today; I took 2.5 g of tartaric acid and
> added distilleed water to 250 ml; that should have given me a 1%
> solution expressed as tartaric.  I then titrated that against my
> 0.103N NaOH and needed 13.1 ml of NaOH to get to an end point of 8.2.
> All of that works out pretty close, given the fact that I was not
> using the best measuring practices; it was right in the ballpark.

> My question is, why use potassium acid phthalate as a standard if this
> works?  Was it dumb luck that the values came out close?

> I had two open bottles of potassium acid phthalate indicate two
> different values, that is the reason I was playing around with this.
> (Both has small black deposits in them, I used the values from the one
> with the least deposit.)  I am going to repeat the experiment with
> more accurate measurements and a fresh bottle of potassium acid
> phthalate.

> Thoughts anyone?
> Regards,
> Joe


 
 
 

NaOH Normality Calibration

Post by Glen Duf » Wed, 27 Nov 2002 21:24:03


Joe,

I use the 1% tartaric acid solution and feel that is stable, cheap and
straightforward.  My only problem is to find someone who can weigh it out
for me.  I also use a simple excel spreadsheet to enter the NaOH adjustment
factor and it automatically calculates my TA when testing wine.

Cheers,
Glen Duff
----------------------

Quote:
> Thoughts,anyone?




Quote:
> > Is there a shelf life on the potassium acid phthalate?

> > I tried a little experiment today; I took 2.5 g of tartaric acid and
> > added distilleed water to 250 ml; that should have given me a 1%
> > solution expressed as tartaric.  I then titrated that against my
> > 0.103N NaOH and needed 13.1 ml of NaOH to get to an end point of 8.2.
> > All of that works out pretty close, given the fact that I was not
> > using the best measuring practices; it was right in the ballpark.

> > My question is, why use potassium acid phthalate as a standard if this
> > works?  Was it dumb luck that the values came out close?

> > I had two open bottles of potassium acid phthalate indicate two
> > different values, that is the reason I was playing around with this.
> > (Both has small black deposits in them, I used the values from the one
> > with the least deposit.)  I am going to repeat the experiment with
> > more accurate measurements and a fresh bottle of potassium acid
> > phthalate.

> > Thoughts anyone?
> > Regards,
> > Joe

 
 
 

NaOH Normality Calibration

Post by Ren » Wed, 27 Nov 2002 21:35:12


For this kind of accuracy needed, tartaric acid does the job well.
Phtalate is the choice for analytical labs. It's very stable, but your
solutions probably became mouldy (the tartaric acid sol will grow
fungus as well in time). Add a preservative or store in the freezer.
NB, if stored in freezer, thaw out COMPLETELY before taking a sample,
as salt gradients are formed during freezing.

Rene

Quote:

> Is there a shelf life on the potassium acid phthalate?

> I tried a little experiment today; I took 2.5 g of tartaric acid and
> added distilleed water to 250 ml; that should have given me a 1%
> solution expressed as tartaric.  I then titrated that against my
> 0.103N NaOH and needed 13.1 ml of NaOH to get to an end point of 8.2.
> All of that works out pretty close, given the fact that I was not
> using the best measuring practices; it was right in the ballpark.

> My question is, why use potassium acid phthalate as a standard if this
> works?  Was it dumb luck that the values came out close?

> I had two open bottles of potassium acid phthalate indicate two
> different values, that is the reason I was playing around with this.
> (Both has small black deposits in them, I used the values from the one
> with the least deposit.)  I am going to repeat the experiment with
> more accurate measurements and a fresh bottle of potassium acid
> phthalate.

> Thoughts anyone?
> Regards,
> Joe

 
 
 

NaOH Normality Calibration

Post by Joe Sallust » Thu, 28 Nov 2002 21:36:44


Glen
You probably have a local pharmacy that still does 'compounding' they
would have a nice scale, also the high school science labs...  Just a
thought.
Regards,
Joe
Quote:

> Joe,

> I use the 1% tartaric acid solution and feel that is stable, cheap and
> straightforward.  My only problem is to find someone who can weigh it out
> for me.  I also use a simple excel spreadsheet to enter the NaOH adjustment
> factor and it automatically calculates my TA when testing wine.

> Cheers,
> Glen Duff
> ----------------------


> > Thoughts,anyone?



> > > Is there a shelf life on the potassium acid phthalate?

> > > I tried a little experiment today; I took 2.5 g of tartaric acid and
> > > added distilleed water to 250 ml; that should have given me a 1%
> > > solution expressed as tartaric.  I then titrated that against my
> > > 0.103N NaOH and needed 13.1 ml of NaOH to get to an end point of 8.2.
> > > All of that works out pretty close, given the fact that I was not
> > > using the best measuring practices; it was right in the ballpark.

> > > My question is, why use potassium acid phthalate as a standard if this
> > > works?  Was it dumb luck that the values came out close?

> > > I had two open bottles of potassium acid phthalate indicate two
> > > different values, that is the reason I was playing around with this.
> > > (Both has small black deposits in them, I used the values from the one
> > > with the least deposit.)  I am going to repeat the experiment with
> > > more accurate measurements and a fresh bottle of potassium acid
> > > phthalate.

> > > Thoughts anyone?
> > > Regards,
> > > Joe

 
 
 

NaOH Normality Calibration

Post by Joe Sallust » Thu, 28 Nov 2002 21:38:14


Thanks Rene, I'll try the freezing trick.
Regards,
Joe
Quote:

> For this kind of accuracy needed, tartaric acid does the job well.
> Phtalate is the choice for analytical labs. It's very stable, but your
> solutions probably became mouldy (the tartaric acid sol will grow
> fungus as well in time). Add a preservative or store in the freezer.
> NB, if stored in freezer, thaw out COMPLETELY before taking a sample,
> as salt gradients are formed during freezing.