A Thermometer of Perturbation

The physics of radiation and understanding the nature of the atom did not consume every scientific imagination at the dawn of the 20th century. Other scientists were busy trying to connect life processes down to the chemical level, rather than trying to build physics up to meet chemistry. The space between physics and biology has always been chemistry's domain.

Other scientists were trying to benefit all of physical science and one prachtig example was  J. H. van 't Hoff*, winner of the very first Nobel Prize in Chemistry in 1901.  Van 't Hoff's prize citation reads "for his work on the laws of chemical dynamics and also osmotic pressure." What van 't Hoff did was to apply mathematical prowess to chemical equilibria, showing how balances shift when heated.

Van 't Hoff's eponymous equation relates an equilibrium ratio, K, to absolute temperature, showing how chemical reactions shift according to temperature. The law holds for chemistry, physics, biology, geology, meteorology—the whole broad swath—anywhere heat affects chemical balance. In a sense, van 't Hoff quantified Le Chatelier's qualitative principle.

A youthful van 't Hoff also made the visionary proposal that tetrahedral carbon existed and that right and left-handed stereoisomers explained observed optical activity, but he thought it wise to exclude such controversy from his PhD dissertation. Watch this video here: link
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*Note the elision of van 't which in Dutch means van het. In German, van het corresponds to von das. Dutch melded the three Germanic genders der, die, and das into just two: de and het.

Ignore The Skidmarks

Thirty years ago and I still recall a problem on a physics final exam at UW-Madison. It went something like this:

A tire is rolling at a constant speed along a pavement. A brake is suddenly applied, bringing the tire to a screeching halt. If the initial temperature of the tire is T_o, what is the final temperature of the tire? You may ignore heat exchange between the tire and road. 

The solution required a couple more pieces of info like the tire's velocity and mass, as well as the heat capacity of the tire.  I omitted those details. I remembered the problem because it was such a nice example of the first and second laws of thermodynamics.

First--all of the kinetic energy (called angular momentum) of the rolling tire changes into thermal energy (heat) as the tire skids to a halt. Nothing is "lost." The rubber in the tire heats up accordingly.*

Second--entropy increases for the energy transformation, meaning that all the well-ordered motion of the rolling tire transforms into the chaotic thermal vibrations of the warmer tire. The second law says that the reverse will not occur. In other words, a rolling tire can suddenly stop and heat up, but heating a tire will never make it roll.
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James Joule spent part of his honeymoon in Switzerland measuring temperature differences between the tops and bottoms of waterfalls. His hypothesis was that the water should be warmer after the kinetic energy of the falling water is converted into heat. There were no forthcoming reports of frictional experiments with his bride.

Boredom Creates Friction

Count Rumford (1753-1814)

Benjamin Thompson (born in Woburn, MA) was the American anti-Franklin. He was a prolific inventor and scientist but sided with Britain during the Revolution and left America after the War and lived abroad thereafter. He eventually settled in Bavaria where he changed his name to Count Rumford and then changed our understanding of the science of heat. And he did all this in the service of practical pursuits.

Rumford oversaw the boring of iron cannon from iron cylinders using a horse-driven drill. He was impressed by how much heat the drilling friction gave off and he designed experiments to measure this. With insulated cannons and submerged drilling experiments, he carefully measured temperature increases. He found that sustained drilling could heat and boil cold water! Collecting and weighing the iron filings, he established that the metal shavings had the same weight and properties as the unbored metal, so nothing had been "given off" as was then currently thought. Rumford concluded that the mechanical work by the horses was converted into heat. Rumford showed that mechanical action can generate indefinitely large amounts of heat, thus directly challenging the caloric theory of the great Frenchman, Lavoisier. 

Lavoisier, a contemporary, didn't live to appreciate Rumford's work--he was guillotined in the French Revolution--ironically for Royalist sympathies. Rumford wound up marrying his widow, Marie-Anne Paulze who was an unappreciated chemist in her own right.

A Conservative Notion of Energy

Julius von Mayer (1814-1878)

The relation between food and work is intuitive: eat or die.* We also think that overeating can be offset by exercise and modern treadmills enable this thinking by showing us calories burned. And while the relation between food and work now seems intuitive, the equivalence of heat and work--or more precisely their interconversion--was a non obvious deduction.

Non obvious because work seems focused--while heat seems dispersed. It took centuries of sustained effort by thinkers and scientists to get us where we are today: that heat and work are equivalent and can interconvert.  Along the way, one man nearly took his own life for want of attention: Julius von Mayer.  His story involved blood, and indirectly, iron. To him we owe the First Law of Thermodynamics:

Energy can be neither created nor destroyed. It can only change forms

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*The German verb sterben, to die, is etymologically linked to our verb to starve.

The Very First Guinea Pig?

Commenter Ritmo's link to the wiki article about dioxin mentioned guinea pigs, which reminded me of Lavoisier, who may have been the first scientist to test theories using that animal. Lavoisier famously taught that combustion was the combining of oxygen with other elements, overthrowing the older notion of phlogiston which I wrote about here.

According to the OED of etymology, the first recorded use of the term guinea pig in a scientific context dates from the 1920s. However, the following description of the work of Lavoisier and Laplace clearly antedates that usage: link to original

Lavoisier's respiration experiments invalidated the phlogiston theory despite protestations from Priestley and Scheele. Lavoisier collaborated with French mathematician Pierre Simon de Laplace (1749 -1827) on problems in respiration chemistry. Their vital experiments with guinea pigs in 1780 first quantified the oxygen consumed and carbon dioxide produced by metabolism. Over a ten-hour period, they collected approximately 3 g of carbonic acid from an animal breathing oxygen. In a second experiment, they placed a guinea pig into a wire cage, which in turn was placed into a double-walled container. Ice packed into the double walls of the outer container maintained a constant temperature; ice between the cage and the inner wall of the container melted because of the animal's body heat. During 24 hours 13 oz. (370 g) of ice melted. Lavoisier and Laplace concluded that the total heat produced by the animal equaled the amount heat required to melt ice. In their own words:

Respiration is thus a very slow combustion phenomenon, very similar to that of coal; it is conducted inside the lungs, not giving off light, since the fire matter is absorbed by the humidity of the organs of the lungs. Heat developed by this combustion goes into the blood vessels which pass through the lungs and which subsequently flow into the entire animal body. Thus, air that we breathe is used to conserve our bodies in two fashions: it removes from the blood fixed air, which can be very harmful when abundant; and heat which enters our lungs from this phenomenon replaces the heat lost in the atmosphere and from surrounding bodies.
...animal heat conservation is thus largely attributable to heat produced by the combination of humid air inspired by the animals and dry air in the blood vessels.

Lavoisier's ideas were radical for 1780 because they connected heat, work, and energy.

Argon Idly Watches The Clouds Go By

Argon: From the Greek word αργον, neut. of αργος [argos] "idle," from α- "without" + εργον "work." = lazy, inactive. Link

Argon is not completely inert. Voracious hydrogen fluoride coaxes some electronic juice out of it, but the two stay coupled only when frozen. Moving further down to krypton and especially to xenon, there is an increasing willingness to redistribute electrons among the noble gas atoms, a consequence of their electronic wealth being more remote from their core and thus more easily removed. 
 
Argon makes up nearly 1 percent of the atmosphere, making it almost 25 times more abundant than carbon dioxide, that vile and evil greenhouse gas. So why is lazy and shiftless argon not implicated in global warming?  For that matter, why isn't air itself (N₂ and O₂) blamed? And why is good ol' water vapor given a pass by the warmists? Those questions have both easy and inconvenient answers.

Greenhouse gases are invisible but retain heat. Argon, being just an atom, never quivers internally, which is how gas molecules absorb and trap heat. So argon has no real greenhouse gas capacity. Nitrogen and oxygen also absorb little heat, even though there are trillions and trillions tons more of them up there. Carbon dioxide absorbs infra red radiation (heat), the sine qua non signature of a greenhouse gas. But water vapor is not only a "better" greenhouse gas than carbon dioxide is--there are also many tons more of it in the sky! (methane is even better than water at greenhouse gassing, but there is so little methane in the air that the point is moot).

So water vapor is by far the most important greenhouse gas. But water vapor also makes clouds which reflect sunlight. That makes clouds the white elephant in the room that the warmists don't really like to talk about. Back in the old days, when environmentalism wasn't so fixated on carbon dioxide, things were more fair and balanced:

If large amounts of carbon dioxide enter the air, then it is quite obvious that a rise in worldwide temperature could result, bringing about the the melting of the polar ice caps. However, an increase in temperatures would also lead to an increased rate of evaporation; with more water vapor in the air, cloudiness would increase. This in turn would mean an increase in reflectivity of insolation, so that less of the sun's energy would reach the earth. The lower temperatures that would result could eventually produce another ice age. Thus we are left with the perplexing thought that increased pollution could cause either a glacial invasion or a worldwide rise in sea levels that could inundate millions of miles of dry land presently in use.

Burrus, T.L; Spiegel, H.J. Earth In Crisis: An Introduction To The Earth Sciences: C. V. Mosby Company: St Louis, 1976 

Talk about putting a damper on global warming.

[UPDATE: link]

Carnot Knowledge: Rudolf Diesel's Awesome Idea

Rudolf Diesel (1858-1913)

Ordinary gasoline engines are powered by the sparked ignition of gasoline vapor compressed with air. The heat of combustion and increased exhaust gas pressure drives pistons, doing useful work derived from the chemical energy stored in the fossil fuel. Gasoline engines behave according to the Otto Cycle and the ideas originally date from the mid-19th century.

Rudolf Diesel, a German engineer, understood the engines of his day and had the radical idea of compressing air inside the piston until it became so hot that fuel would spontaneously ignite when it contacted the hot pressurized air, thus not requiring a spark plug. In essence, Diesel reengineered the existing Otto cycle and invented engines that behaved according to the Diesel Cycle.

Diesel based his ideas on his understanding of the thermodynamics of heat engines, a young science begun by the French engineer Sadi Carnot and who later became known as the father of thermodynamics.

US Patent No. 542,846: "Method of and Apparatus for Converting Heat into Work (Link) was awarded to Diesel and has a clear and concise explanation of how and why diesel motors work. In Diesel's own words (or more likely those of his patent attorney):

The gases in the cylinder are now permitted to expand with gradual introduction of fuel and expansion is so regulated that the decrease in temperature by expansion counterbalances the heat produced by the combustion of the fresh particles of fuel. The effect of combustion will therefore not be increase in temperature or pressure, but increase in actual energy exerted.

Diesel also solved another important problem that still limits the efficiency of gasoline engines, viz., the tendency for gasoline motors to knock or ping due to "predetonation." Autoignition is precisely what diesel motors are supposed to do, albeit in a controlled way.  In a diesel motor, the air and fuel are pressurized separately and then mixed. Because diesel motors burn at hotter temperatures than gasoline engines do, they have a tendency to "burn air," forming nitrogen oxides from the normally inert N₂ and O₂ that make up the air we breathe. Precious metal catalysts are used to convert the nitrogen oxides back into oxygen and nitrogen.

Today, diesel motors find widespread use in nearly all commercial transportation applications: trucks, trains, ships, submarines, and, as I learned from Theo Boehm, even in aviation (BTW, did you know that aviation gasoline still has lead? Link--fine particles of lead oxide (or actually lead chloride or bromide) rain down on us everyday. Europeans use diesel motors far more commonly than we do for personal transportation.

I'm sold on diesels. I own a 2003 VW Golf Diesel (TDI) and I love it. It gets around 43 MPH on the highway and not much less in city because it's a stick. Another advantage to owning a diesel in CA is that they are exempt from smog-testing.