Yea, that’s how most patent lawyers talk.
They are using standard buffering chemistry. MES is a buffer. Mono-potassium phosphate + Di-potassium phosphate forms a buffer (this one you can formulate a nutrient solution that provides both nutrients and has buffering capacity).
Using a strong acid and/or a strong base (potassium hydroxide) allows you to adjust the PH but it does not add buffering capacity by themselves (it removes capacity for a buffer with a single pKa, more on that in a moment). What you’re probably looking at, with the addition of a strong base, is the adjustment of the PH with the buffering complex occurring in solution (that is the other side of the buffer is there already). Adjusting the ratios allow some tuning.
Going deeper:
A buffer is not “rock steady” at certain PH. Instead it adds “resistance” to changes in PH.
A buffering complex has a pKa value(s). This is the point of maximal buffer capacity and is the key to the buffer PH compatibility. As you add an acid or a base to a buffered solution, the PH will begin to deviate away from the pKa. The buffering complex will resist a change in the PH as the buffering compounds will react with any added acid or base. The further away from the pKa you move, by adding more acid/base to the solution, the faster and more dramatic the PH change will be (you have less buffering capacity, one component of the complex is being used up). Eventually you reach a point where there is no longer any buffering available.
Many of the buffers in literature have pKa values that would be useless for horticulture. The general rule is you can adjust the PH of a buffered solution ~ +/- 1 PH and still retain some buffering capacity. Some buffers will have a pKa that’s greater than one PH away from our target PH. Since the adjustment would need to be > 1 PH, those aren’t terribly useful for us.
The few safe buffers that have a pKa near the PH we’d be interested in, can also be tuned by adding a strong acid/base within +/- 1 PH and still have some buffering available.
To formulate a buffer, you’d want the pKa to be as close to your target PH as possible (for maximum capacity). Then you can tweak it with a strong acid or a strong base. Of course, the buffer chemistry needs to be compatible with plants and humans.
When it comes to quantity, the more you add the more buffering capacity you have. Add less, less capacity. Sometime you’ll have no choice but to have a non-optimal capacity by adding less than you would like.
But, be assured, you are providing some buffering.
Before trying to determine quantities, we need to look at reality. The reality is that the chemistry of a complex solution is, ugh, complex. The environment, the biological activity, the chemistry of added nutrients, etc are going to affect the solution PH. You may have many unexpected buffering complexes being formed and, overtime, reactions in the chemistry can change the behavior of the buffers. Buffering is not an end-all solution. What is does provide is more stability, if you have the buffers with a pKa that matches your goals. Expect some drift.
Now let’s consider:
We have some RO water and two chemicals. The chemicals are some sort of a strong acid and a strong base. If we add the acid in copious amount we’ll end up at some plateau that similar to the PH of the acid itself. Likewise for a strong base. The left portion of the graphic is lots of acid while the right show lots of base.
If we start “titrating” the solution by adding small amounts of the base to an acid rich solution, for example, we’ll pass through the point of equivalence. This is where the effect of the acid is equivalent to that of the base(H+ and OH- are equal = PH of 7). Small changes in the quantities of either the acid or base will cause a rapid and wild swing in the PH (the slope is large).
Ok, so let’s look at a weak acid and a strong base:
Starting at the left side of the graphic, we have some RO water with a weak acid added. As we begin to add a strong base, you’ll note that the PH is rising. But it rises quickly, then slowly, then a wild swing. The point where the PH slows is the buffering region (note the pKa). In this buffering region you can add strong acids or bases and the solution will resist PH change.
And, this is the problem we face:
We use RO to remove the unknown chemistry and any other stuff we’d like to avoid. This leaves us with a relatively blank slate with neither an excess of H+ or OH-. It allows us to build upon a procedure to develop a solution that is repeatable by reducing the effect of the source water chemistry. From this point forward, unexpected PH fluctuations are entirely due to other variables.
Watch these for a background:
ways-to-get-a-buffer-solution
ph-and-pka-relationship-for-buffers
Some of the variables we can never know for certain and one is left with experimentally determining the effect of the chemistry added, the effect of the environment, and the effect of the system/biology. Break the problem down into distinct steps and you’ll get an idea of how each step affects the PH. You can get an idea of how your solution will behave by titrating the solution with a strong acid / strong base to get an idea of where the buffering exists. If any.
