Field of Science

Climate Change Skeptics

Paul Krugman has a piece on climate change on his blog at the NY Times. One commenter responds:

"One thing they are "gong" [sic] to do is point out that if the ppm increase in atmospheric CO2 is solely due to man-made combustion of fossil fuels, laws of chemistry and physics have been violated. For every molecule of carbon, two molecules of oxygen are consumed. Therefore, if the rise in CO2 is due to such combustion, then we should observe a decrease in atmospheric O2 by a factor twice as great. I have seen no evidence to suggest that global O2 is decreasing at all." (H. Muhlphart )

Ouch! My response:

No law of chemistry and physics has been violated by assuming that the increasing CO2 comes from combustion of fossil fuels. The reason no decrease in O2 is "noticed" is because the loss due to the formation of carbon dioxide is very small compared to the total amount of oxygen. If you increase the amount of CO2 by 100 ppm (more or less what's predicted in the next 50 years), the decrease in O2 is from 209,460 ppm to 209,360 ppm. That's the equivalent of being at the top of less than a 30 foot hill. You certainly don't notice any change in the oxygen levels between the basement and second floor of a house, do you?

And I didn't even bother with the notion that carbon dioxide "eats" two oxygen atoms no matter what carbon source you make it from - fossil fuel or respiration. Or that it's one carbon atom to one oxygen molecule. At this level of understanding of the basic science, you are not simply not entitled to an opinion on the matter.

Chemical Urban Legends: pH

What does the p in pH stand for?

The term pH has been in use for more than a century. It is a logarithmic measure of the hydrogen ion concentration ([H+]): pH = -log10[H+]. (Technically, there aren't bare protons (H+) floating around in solutions, but that wasn’t known when pH was introduced!) The original symbol used by Sorensen was pH+.

Theories vary as to the origin of the p - most agree it means power but whether in Latin, French or German, seems in dispute. Thinking it would be either French or Latin as the original paper was published in French, I was surprised to find that it's neither, though the legend is both old and persistent. By 1920, many authors were assuming that it meant “power”, but Jens Norby returned to the original sources and points out that it was the arbitrary choice of the letters p and q for two variables in the work-up of the experimental data. The variable p eventually ends up in the formula arrived at for the concentration of the hydrogen ion.

The modern form pH was introduced in 1920, "as a matter of typographical convenience".

For the full explanation, see Jens G. Norby, The origin and the meaning of the little p in pH, Trends in Biochemical Sciences 25, 36-37 (2000). The illustration is a selection from the original paper: Sorensen, Compt. redn. du Lab. de Carlsberg 8 1-168 (1909).

Open Laboratory 2009

Open Laboratory 2009 - a juried anthology of the best of the science blogosphere from last year has appeared. Edited by scicurious, it's available here. I have a piece in it - a cleaner version of this post on the use of helium to preserve documents. I'm fascinated with the interplay between web and print that ultimately produces this volume.

Want a copy? Order one -- or if you're feeling lucky, de-lurk and leave a comment before March 5th and I'll draw a winner at random. The rest of the pieces look great - on everything from the flu to charismatic megafauna (whales and chimps) to the statistics of human milk production.