Kent Marine pH Stable

I don't suppose anyone has an opinion of Kent Marine pH Stable?

The label states the contents as Carbonic Acid Monosodium Salts.
Strangely enough, it is supposed to increase buffering capacity.
Stranger yet, I can never get the increase to show up with a test kit.
I haven't put any in the tank since I can't  get it to work in my test
cases. It also states that it may take up to 24 hrs for the change,
but I didn't read any change in that amount of time. Perhaps there
is something else in the "equation" that is not in RO water?

The problem is that by the time I get RO water buffering capacity
up to ~80 ppm  using baking soda,  the pH is ~7.5.

Surely I'm not the only one who has noted this.

Jon Wilson
jwilson at b856s3_ssc.af.mil