Stainless Steel Tank Material Grade and Wall Thickness Needed

We are looking to have an Ammonium Persulfate tank fabricated. Stainless steel has been mentioned numerous times but no one has been able to tell me which grade (304, 316, etc). The Ammonium Persulfate concentration will be 10% by weight.

Also, the above tank (and several more down the line) will hold approx. 125 gals of liquid and the tank size will be 33"W x 33"L x 36"H, free standing (no support framework), 1 1/2" lip at the top, hinged cover. What gauge of SS would be normal (16?)? For additional durability increase gauge to 14 or 12?
(The Ammonium Persulfate tank will also have a containment tank).
Thank you,
Tom