Okay, that's our PH. Now, as I begin slowly adding drop by drop, what will happen to our PH? Well, it will increase. Right, but how will it increase? Well, let's look at the graph of PH versus volume added, where PH is the Y axis, and volume added of our base in this case is the x axis. So according to this graph, we see that the relationship is based on a sigmoidal curve.