Now, usually these acid reactions, acidbased reactions take place in water because our body consists predominantly of water. And so we have a water molecule that will grab the H ion using one of its lone pair of electrons on the oxygen to form the following hydronium ion. Now, the next question is what exactly is the method by which we calculate we measure the hydrogen ion concentration inside solution. So we use something called the PH. And the PH is nothing more than a fancy way of determining what the concentration is of our solution. So the PH is equal to negative log of the hydrogen ion concentration in that solution.