That Dakins solution is a newer formulation with the small amount of baking soda added as a buffering component agent. It adds nothing to the benefit of swishing over your teeth and may actually cut that benefit down a little bit because it dilutes the percentage of chlorine in the final mix. Not much but some. The pure solution is stronger.
We leave it out, and historically it's been left out. The baking soda in the formula merely allows the solution to be kept for more than a few minutes, but the problem with that is that you have no idea how long that buffering will allow the adequate strength to last! You may wind up using a solution that is too weak to be effective. It is better and safer to take the time to make your solution as you need it.
The best brand to use is the Clorox brand with the blue cap. That is the purest, without adulteration, and always a known, fixed percentage at the time of purchase that we know of. Other brands may be just as good, but none of the others are FDA approved to make Dakin's Solution. As you use it, it can only get weaker, not stronger as the chlorine component is more volatile than the water in it. You cut it to the 20 H2O to 1 Clorox ratio and you'll be OK.
The pure Clorox burnt.....lol.. Just kidding, I mixed it 20-1 and it does leave you feeling like your gums are clean. After 15 minutes I swished Hydrogen peroxide, and there was no bubbling. I took that to mean there was little food or bacteria left after the cleaning. I am trying this for the next month and see if it results in better health. Of course once I get into it, it will just be another habit I won’t break. Thanks for the information.