alternate preception of ph


New member
i'm one of those people who attaches the + to the - before rethinking it when i have to jump start a car, which isn't very often....

in sort of the same way, when i think "low" ph, my mind automatically goes to a lower concentration of hydrogen ions, rather than higher as it should

i find i have to redirect my train of thought in that split second

just wondering if an alternate unit of measure for ph or the free h+ has or is used, or if there is or isn't any reason why one would or wouldn't be more appropriate, or if anyone else has similar thoughts or something insightful to add on the topic?

for example would a hc (hydrogen concentration) unit of measure make more litteral sense, or is there a practical reason to refer to ph?

could it be becasue i'm thinking of each checmical in the solution equally and not as a water centric solution?

curious to hear some outside perspectives...


-RT * ln(k)
Sure, you can use hydronium concentration, but most everything to do with pH varies on the logarithmic scale so that's what we use. Its also important to know that when looking at pH a solution oat pH 1 has ten times more H+ than a solution at pH 2 and a hundred times pH 3. So looking just at concentration it would seem like there's way less difference between 6 and 7 than between 2 and 3.

Randy Holmes-Farley

Reef Chemist
Premium Member
Simplicity is the main reason.

There are several reasons that pH is used instead of [H+], not the least of which is it simplifies discussion of H+ concentrations that range over 15+ orders of magnitude.

For reefers, the main reason to use it is that all of the history of reefing and chemical oceanography use it, as do all of the commercial devices used to measure it.

Another reason is that it is often not the actual concentration of H+ that we care about, but any of a dozen other implications of the measurement that we care about, such as the amount of OH-, the concentration of various magnesium ions such as MgOH+, the ratio of HCO3- to CO3--, the rate of dissolution of CaCO3, etc.


New member
as usual, i think i might be getting a handle on it, and the equation splits up into exponentially smaller values :spin2:

and thanks as usual guys :beer:


-RT * ln(k)
Exponential is the key word. If you think in terms of [OH-] instead of [H+] it doesn't feel backwards.

Some useful equations if you want to learn about pH:

pH = -log[H+]

pH + pOH = 14

[H+][OH-] = 10^-14

pH = pKa + log ([A-] / [HA])