That's University of Virginia's buffered Dakin's solution that will allow you to keep the Dakin's Solution for a few days. That's not really necessary. You can mix straight un-buffered Dakin's as needed for immediate use without boiling, using straight tap water and no baking soda. You just have to make it every time you use it and throw it away because it doesn't "keep." The problem with the Buffered Dakin's Solution is you don't know how long it is effective. With the unbuffered, made when you need it, you know it is effective.
That being said, if you are going on a short trip, the buffered is a good way to take some with you so you don't have to take a bunch of separate fixings with you. Mix it up, seal it in a bottle tight so no air gets in between uses, and you are good to go for about a week.