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fffH? Ffhah? What's that? Oh, like shampoo? Does it have pH in it? What is pH? Who the dickens cares? Why is it that this "window" into water quality (chemistry/physics) is such a powerful tool/consideration? Here's my version of... See more » fffH? Ffhah? What's that? Oh, like shampoo? Does it have pH in it? What is pH? Who the dickens cares? Why is it that this "window" into water quality (chemistry/physics) is such a powerful tool/consideration? Here's my version of what everyone should basically (pun intended) know about what pH is, it's importance & what you can & should do about it. What: pH is a Measure. The symbol pH is a contraction standing for pondus Hydrogenii (=the "weight of hydrogen", the simplest element); pH is the relative measure of hydrogen ion concentration. Put another way, pH is the relative presence of H+ (Hydrogen ions) versus OH- (= Hydroxyl ions). Note when these two types of charged species get together they form an uncharged water (H2O) molecule. You finally will understand this. In a "pure" solution of nothing but water there is a concentration of @ 10-7, that's ten to the minus seventh (0.0000001), or one in ten million molecules of water that on average have fallen apart/& are getting back together. The fancy mathematical expression for pH is that it's the negative (or one over, the reciprocal) of the logarithm (base 10) of hydrogen ion concentration, or -log10 [H+] or 1/log10 [H+] In our example of "pure" water this is log10 [10-7] or the log of one over 10 to the minus seven which is a pH of 7.000. Ahhhh. Yay! All that pH is is a measure of other "stuff" dissolved in the solution that affects (net increases/decreases) the concentration of Hydrogen (&/or Hydroxyl) ions. Making the average number of hydrogen ions greater (e.g. 10-6, 10-5, less 10 to the minus negative) means the pH is lower (!) See? Or more acidic (by definition). Going the other direction, having less concentration of H+, meaning the 10 to the minus power is more negative, denotes an alkaline, or basic condition. As an example, consider a hydrogen ion concentration of 10-8 = a concentration of 0.00000001 H+ ions, denotes a pH of 8.000. A 7.000 situation is termed a neutral pH. Makes sense to me. Maybe one last example (or two). Let's say the hydrogen ion concentration is 10-7.8 or 0.00000078. What is this solution's pH. That's right, 7.8, like much of our beloved southwestern "liquid-rock" tap water. Note that in the above expressions the change between a pH point, let's say seven and eight represents a change of an order of magnitude, or ten times. Much like the logarithmic scale (Richter) used to describe earthquakes, a small difference in number represents a large change in hydrogen ion concentration. Going from a pH of 6.5 to 4.5 is a difference of 100 times less concentration! This is a big difference, and you should be aware and wary of the logarithmic nature of the pH scale. I'll leave it up to the Big Editor, Don Dewey, to leave in/out mention of the upper/lower limits of dissociation of acids and bases, pH's of 0 to 14 under conditions of complete/full dissociation. Reserve/Resistance to pH Change: The capacity of a system to resist an upward (example 7.0 +) or downward (less than 7.0) pH is termed Alkalinity and Acidity respectively. The same quantity is in turn referred to as alkaline and acidic reserve. Read those last two sentences again, carefully. This understanding seems easily lost amongst aquarists. In actual practice what happens is there are materials, chemicals suspended and dissolved and capable (like gravel, coral...) of dissolving (or going into solution), one's added intentionally as foods, treatments, source/tap water constituents that "fight" or resist change in pH. This is what we mean by buffering. Buffers aid/thwart efforts in changing chemistry/physics by resisting shifts (in pH in this case). This is the reason Alkalinity/Acidity tests must be applied in conjunction with simple pH, if much adjustment is needed/desired and/or you're dealing with expensive or sensitive livestock. There may be so much buffering capacity at different levels or points in the system's pH make-up that you may accidentally overshoot and drastically/tragically raise or lower the pH too much too soon. I cannot but begin to tell you how many times I've seen See less »

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aquarium, water chemistry

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/The Conscientious Aquarist

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