Optimum pH range for long-term storage of aqueous sodium hydroxymethanesulfonate solution

[easypeasyac]

Hello;
While some sources say that the pH range of 4-6 is most suitable for the stability of the solution, some sources indicate the pH range of 7-8.
What is the most suitable pH range for storing aqueous sodium hydroxymethanesulfonate (CAS 870-72-4) solution for a long time?
Thank you.

[ChenBeier]

Alkaline is better, if you have acidic pH it decompose to Formaldehyde, sulfur dioxide and water.

HOCH₂SO₃Na + H+ => HOCH₂SO₃H + Na+
HOCH₂SO₃H => CH₂O+ SO₂ + H₂O

[easypeasyac]

Thank you for your reply @ChenBeier;

When I adjust the pH of the solution to 7.5-7.7, I start to smell a faint formaldehyde odor. At pH levels of 6-6.5, the formaldehyde odor is still present, but less so. Is this smell a sign of decomposition?

[ChenBeier]

Yes that is it. More acidic the formaldehyde will gas out. Go to pH 8 to 9 the smell should almost disappear, but not 100%.

Also HOCH₂SO₃Na => CH₂O + NaHSO₃ will decompose slowly.
Stable is it only in solid form. Recommendation is to make everytime fresh solutions.