[mayfebiani]

Hello Everyone, I am currently working on determining calcium concentration in milk using EDTA titration(direct titration and back titration). It has been working pretty great. But there is one question that keep spinning in my mind!

To standardize the EDTA solution, I need to make the Standard Calcium Solution,using Calcium Carbonate dissolve with dilute HCl, then dilute with distilled water(all of the paper that I read as the reference use this procedure).
One day, my teacher ask me,"Why don't you use the Calcium Chloride instead?".*BAM* that hits me.

In my opinion, there is no difference, or maybe a slight difference of pH. But, I dont think there will be a problem since it's only for standardizing the EDTA solution. Or maybe there will be a problem in the back titration since I need to put some of the calcium solution?

I try to find the answer in the internet also. But, cant find it. (I found the same question in a book instead, with no answer). Is there any reason why all the researcher use calcium carbonate instead of calcium chloride???

Hope my question is not that stupid.(that's why I can't find it in the internet maybe.)
Thanks in advance..

[Borek]

http://www.titrations.info/titration-standard-substances