Laboratory manual of biological chemistry : with supplement / by Otto Folin.
- Otto Folin
- Date:
- [1934]
Licence: Public Domain Mark
Credit: Laboratory manual of biological chemistry : with supplement / by Otto Folin. Source: Wellcome Collection.
29/388 page 15
![(and its alkalinity the same small fraction of that of a normal solution of sodium hydroxide). On this basis, neutral, acid and alkaline solutions may be redefined in more definite terms, as follows: Neutral solution: [H+] = icr7 n= [OH-] Acid solution :3 [H+] > io-7 n> [OH-] Alkaline solution : [ H+] < icr7 N< [ OH-] Hydrogen Exponent.—To avoid the use of unwieldy figures, like that given above (p. 9) for the [H+] of tenth normal acetic acid (0.00136 N, or 1.36X10-3 n), hydrogen ion concentrations are ordinarily expressed as logarithms. The logarithm of 1.36X io-3 = log 1.36 + log io-3r=o.i3-f (—3.00) = —2.87. This, with the minus sign omitted, is called the hydrogen exponent, or pH, i.c., the pH of tenth normal acetic acid is 2.87. The value for the [H+] of any solution (aXio4) may be converted into this sys¬ tem by subtracting log a from b, or, pH = & — log a. Below are given the hydrogen exponents corresponding with a series of hydrogen ion concentrations ranging from 0.01 n to 0.001 n, to illustrate further the relation between the two methods of expression. [H+] O.OI =I XIO-2 N o.oo9 = 9X io-3 n 0.008 = 8X io-3 N 0.007 = 7 X io-3 N o. 006 = 6X io-3 N 0.005 = 5 XIO-3 N o.oo4 = 4X io-3 N O. 003 = 3 X IO-3 N 0.002 = 2 XIO-3 N O.OOI — I X IO 3 N pH 2 — o. 00 = 2.00 3-0.95 = 2.05 3 — O. 90 = 2 . IO 3-0.85 = 2.15 3—0.78 = 2.22 3-0.70 = 2.30 3 — o. 60 = 2.40 3-0.48 = 2.52 3-0.30 = 2.70 3 — o. 00 = 3.00, etc. 3 The word “acid” is used both as a noun and as an adjective, and these. two uses must he sharply distinguished. Water is an acid («.) because it dissociates into hydrogen ions. It is neutral (that is, not acid (adj.) or alkaline) because neither the H + nor the OH— is in excess. Water is both an acid («.) and a base, but nothing can be both acid (adj.) and alkaline.](https://iiif.wellcomecollection.org/image/b29928588_0029.jp2/full/800%2C/0/default.jpg)
