[Japo]

Hello,

We're trying to detect trace nitrates and we've found (unequivocally we believe) that an ultra-pure HCl 37% solution is contributing a certain amount of nitrates. According to our approximate quantization the amount may be within the limit promised on the label (~1 mg/l), but in our application that's too much background noise.

We're not managing to better the original purity ourselves (surprise) by distillation. (No wonder since the boiling point of the 20% HCl azeotrope is 109º C?) Can anyone think of some substance that could be added to the solution so distillation may work better, allowing us to purify the HCl+H2O leaving the nitrate behind? Perhaps a cation that forms a very stable salt with the nitrate but doesn't react with the chloride?

I'm not chemical by education so I may be missing something very obvious or talking nonsense, but our chemists can't think of anything right off the bat either. Thanks in advance.

[vmelkon]

Since hydrochloric acid evaporate easily, you can put a beaker full of HCl in a larger container. Then, have another beaker with pure water and place it inside the container. The HCl will migrate into the water.