In a message dated 6/16/00 3:28:42 PM EST, [email protected] writes: << Ammonia 1N = 11.6 Ammonia .1N = 11.1 Ammonia .01N = 10.6 NaOH 1N = 14 NaOH .1N = 13 NaOH .01N = 12 HCL 1N = .1 HCL .1N = 1 HCL .01N = 2 The ph is a log scale. In the case of ammonia a 100 to 1 change in concentration gives only a 10% change in the ph.
Marshall: I think this example is misleading because at very high pH ammonium hydroxide is only partially dissociated. We are at the other end of the spectrum where there is TOTAL dissociation of these species if, in fact they are present in any significant concentration (which I seriously doubt). Under these conditions, a 10:1 dilution brings the pH ONE UNIT closer to 7 from either direction. For most purposes pH can be equated to the negative logarithm of the hydrogen ion activity. From General Chemistry 6th edition: "Mixtures of weak acids and their salts or mixtures of weak bases and their salts are called buffer solutions. They resist a change in hydrogen-ion concentrations upon the addition of small amounts of acids or bases. An example of a buffer solution is a mixture of .1M acetic acid and .1M sodium acetate. The ;pH of the solution may be found as follows (I don't now how to key this stuff in :< ). This subject is really rather complicated, and I would suggest obtaining a college chemistry book and reading the section on pH. It is beyond my ability to totally understand it myself, and certainly to try and explain it. There is one interesting reference in here that touches on what has been discussed before: Water in equilibrium with the air contains 4.4X10^-5% by mass of carbon dioxide. The resulting carbonic acid H2CO3, gives to the solution a hydrogen ion concentration about 20 times larger than that of pure water, or 2.0X10^-6 as compared with 1.0X10^-7. thus the pH is: pH = -log[H+] = -log(1.34X10^-3) = -( log 2.0 + log 10^-3) = -(0.127 - 3.00) =2.873 Thus according to this reference if you let pur water sit in the air, it will absorb carbon dioxide and end up with an acid ph of slightly under 3! Marshall: No way can carbonic acid reduce the pH under 3!. Test the pH of soda water which is UNDER CO2 PRESSURE. Want to take bets on the pH you'll find? A pH under 3 probably wont give you stomach pains though because it would probably be completely consumed burning up your esophagus. Roger -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: [email protected] -or- [email protected] with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
