Followed the instructions. 6.2 gm in 50ml yielded a solution that was 7.
I'm using that Arm & Hammer 5# bag that comes from CostCo converted to Sodium Carbonate at 200C (390F) for 1 hr.
Getting a milligram scale later today. My M1 standards won't be here for a few weeks though.
Will cal with a M2 for now.
Will post my formula for 8.5 PH stuff asap.