Conservation DistList Archives [Date] [Subject] [Author] [SEARCH]

Subject: Alkaline reserve

Alkaline reserve

From: Doug Nishimura <dwnpph>
Date: Friday, August 10, 1990
As for the alkaline reserve problem, it would not surprise me to see
paper that was buffered that couldn't maintain its alkalinity.

1) The initial pH of the paper will play a role.  A buffered paper that
starts at a pH of 7 will not resist acid attack as well as a similarly
buffered paper with an initial pH of 8.5.

2) The quality of the paper is important.  A poor quality buffered paper
that is producing acids internally will not resist environmental acid
sources as well as a high quality buffered paper that is not producing
acidity internally.

3) Any alkaline reserve is finite.  Consider a paper that is 60g/sq.
meter. For ease in calculation, suppose that the paper contains 10%
calcium carbonate -- a rather high figure.  (I have found microfiche
envelopes that were very close to 10%.)  One square meter of paper
contains 6 grams of calcium carbonate.  If we follow the titration
curve, the carbonate changes to bicarbonate at about a pH of 8.  The
next conversion point (bicarbonate to carbonic acid) is at about a pH of
4.  The calcium carbonate can therefore absorb a little more than one
equivalent of acid before it approaches a pH of 7.0.  One square meter
of paper can absorb about 3.6 grams of acetic acid before it becomes
acidic (assuming that all alkalinity is from calcium carbonate).  In
rough terms, that amounts to about 4 tbsp, 2 1/2 tsp of vinegar.  In
addition to poor quality paper, industrial pollution is a big source of
acidity.  (My home town in Canada was publishing the pH of rain in the
paper every week and it has been as low a 4.3.  I'm from a town almost
halfway between Ottawa and North Bay -- about 120 miles northwest of
Ottawa.  The town is not in the middle of an industrialized area.
Ottawa is the nearest major city.  I imagine that rain in more
industrialized areas would be much worse.)  Drying oil type paints
(alkyds) and varnishes are also notorious sources of low molecular
weight organic acids (not to mention peroxides).  Most papers I've seen
are closer to 3% calcium carbonate  (about 1 tbsp, 1 1/3 tsp of

                           -Douglas Nishimura

                  Conservation DistList Instance 4:10
                  Distributed: Friday, August 17, 1990
                        Message Id: cdl-4-10-003
Received on Friday, 10 August, 1990

[Search all CoOL documents]