View Single Post
  #7   Report Post  
posted to rec.boats
keith_nuttle keith_nuttle is offline
external usenet poster
 
First recorded activity by BoatBanter: Aug 2006
Posts: 14
Default Oceans turning acidic Accuracy of the pH measurement

Insignificant in this case was used in a statistical sense. The
difference they are attributing to global warming is smaller than the
error in the instruments they are using for the measurement.

In other words they would see greater differences on multiple
measurements on the same solution in the lab, than the difference they
are attribute to global warming,

There are no instruments capable of detecting the difference attributed
to global warming being made today.

It is like measuring teaspoons size quantities with a gallon container.

Or setting up your table saw with a cloth sewing tape measure.


basskisser wrote:
keith_nuttle wrote:

I was in the laboratory measuring pH when I read the article published
on the increasing pH because of global warming.

If you read the original article you would see that the difference in pH
they are talking about is in the neighborhood of 0.03 pH units. This is
insignificant and does not indicative anything except the precision of
the pH measurement and the sampling. Since the difference is the
precision of the measurements there is nothing to do with global warming.

pH is a theoretical amount of Hydrogen molecules in the solutions. In
practice pH is a measure of the impurities in water, and is
significantly affected by the temperature of the solution. It is also
affected by the actual materials in the solutions as the the amount of
Hydrogen ions are affected by the interactions of the compounds in the
solutions.

pH is measured using the electrical properties of the solution. Because
of the quality of the electronics the precision of the measurements are
several powers more accurate than the precision of the chemical
properties that are being measured.

The electronics are standardized against two reference solutions. The
accuracy of these solutions is about +/- 0.01 based on the suppliers of
the standards. See a typical specification sheet for one of those
standards is at

http://www.coleparmer.com/catalog/pr...sp?sku=0594242

In practice the precision of laboratory measurements of pH is about +/-
0.03 one one sample. When you take dozens of samples there is
additional error. So you can see the differences they are trying to get
funding to study is nothing but the precision of the measurement of the
pH. (If you google you can find many papers on the laboratory precision
of pH measurements.)

Because of the inaccuracy in pH, the specifications for the drugs you
take are usually stated to 0.1 pH units.

Now, if someone can explain to me how they can say there is a 0.4 degree
change in the mean temperature of the earth when the daily temperature
difference across the surface of the earth is about 100 degrees. I don't
know much about temperature reading and statistics.



It isn't insignificant when you think of it in global terms. The same
thing with temperature.