Thermodynamic acid dissociation constants of prospective buffer substances
Jesus M. Castagnetto
[email protected]
http://www.geocities.com/ResearchTriangle/Lab/1059/
Created: April 20, 1998
Updated: May 28, 1998
UPDATE: Added the reference to the book used to generate the JFile DB
CONTENTS
buffers.pdb - JFile DB of buffer substances w/ thermodynamic info
univbuff.txt - Memopad formated file for preparing an approximated
universal buffer.
DESCRIPTION
The JFile DB contains the pKa for the respective buffer substance
(most at 25 C; for other conditions, see notes below), the name
and corresponding d(pKa)/dT coefficient where available.
The notes below, are also included in the DB and pertain to
values obtained at different conditions:
Notes:
[1] "Apparent" or "practical" constant for 0.1M solution, 20C
[2] "Apparent" or "practical" constant for 0.05M solution, 18C
[3] "Apparent" constant, I = 0.025
[4] "Apparent" constant, I = 0.1
[5] pKI' = 4.36 (c = 0.01M)
The Memopad file indicates the proportions in which solutions need
to be mixed to obtained an universal buffer solution in the range
of pH = 2.0 - 12.0
DISCLAIMER
The information here is provided as is, and you assume all the
responsability of its use/misuse and its correctness or fitness
for a particular purpose.
(Don't you hate disclaimers :)
ACKNOWLEDGMENT
Thanks to Marieke Thayer at TSRI for the idea of making this
info available.
REFERENCE
The data used to create the JFile DB and the Memopad file come
from the book:
"Buffers for pH and Metal Ion Control"
by D. D. Perrin, Boyd Dempsey
Chapman & Hall, New York, 1983
Approximate Universal Buffer
(From Carmody, 1961)
Transcribed by:
Jesus M. Castagnetto
[email protected]
http://www.geocities.com/ResearchTriangle/Lab/1059/
Created: April 20, 1998 (Updated/Released: May 22, 1998)
Instructions:
To prepare a buffer with a total volume of 200 ml, using x ml of a solution 0.2M in boric acid and 0.05M in citric acid, and (200 - x) of a solution 0.1 M of trisodium ortophosphate.12 H2O (*)
pH x
2.0 195
2.5 184
3.0 176
3.5 166
4.0 155
4.5 144
5.0 134
5.5 126
6.0 118
6.5 109
7.0 99
7.5 92
8.0 85
8.5 78
9.0 69
9.5 60
10.0 69
10.5 49
11.0 44
11.5 33
12.0 17
Note:
(*) The pH values are approximate because of veriation in composition of commercially available trisodium phosphate. This table was based on the use of commercial reagent containing approximately 2% NaOH.
Table from Carmody (1961) J. Chem. Ed., 38, 559 in the book
"Buffers for pH and Metal Ion Control"
by D. D. Perrin, Boyd Dempsey
Chapman & Hall, New York, 1983
DISCLAIMER: Use the information in this document at your own risk.
