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