Tuesday, 13 October 2009

Fixed Air Part I

In 1755 Joseph Black is credited with discovering "fixed air". It was named as such because it was fixed or trapped in certain organic compounds. Black first obtained it by heating the mineral limestone (calcium carbonate) until it decomposed into a gas and left behind lime (calcium oxide). The gas given off could be made to recombine with calcium oxide to form calcium carbonate again. Today we know this gas or "fixed air" as carbon dioxide (CO2).

Black also showed that when calcium oxide was allowed to stand in air, it turned slowly to calcium carbonate. From this he deduced that there were small quantities of carbon dioxide in the atmosphere. Thing is, there seems to be a very small amount of carbon dioxide in the air we breathe - it's something like 0.03%. Carbon dioxide simply does not seem to exist in the air.

The following extract is taken from Joseph Priestley's treatise of 1796 ~ "Considerations on the Doctrine of Phlogiston, and the Decomposition of Water". In it, Priestley confirms the difficulty of extracting carbon dioxide from the air. He also reveals the phlogisticated nature of carbon dioxide.

"Fixed air is procured in great abundance in animal respiration. It is true that fixed air is procured by exposing lime-water to atmospherical air, but it is never procured by this means in air confined in any vessel. There must, for this purpose, be an open communication with the atmosphere, but fixed air will be procured in great abundance by breathing air contained in the smallest receiver, and especially if the air be dephlogisticated. It must therefore be formed by phlogiston, or something emitted from the lungs, uniting with the dephlogistcated air which it meets there."

I think Priestley was a little more than intrigued by fixed air. I wonder why it is that lime-water is affected by atmospherical air, and not the air "confined in any vessel". I wonder if the figure of 0.03% for carbon dioxide is taken from the atmosphere or a confined vessel?

In a series of experiments Priestley exposes something about carbon dioxide that I, as yet, have not seen noted by any other experimenters. Priestley said that he had found that fixed air "contained half its own weight in water". According to science textbooks, the atomic weight of carbon dioxide is 44 g/mol.

Now I find this fascinating as Priestley appears to be telling us the atomic weight of water. I don't think the atomic weight of water is 9, as defined by adding the atomic weight of hydrogen (1) to oxygen (8), because I suspect the hydrogen we find outside water is empty of phlogiston and is not directly the same stuff that exists in water. I think water is rich in phlogiston. I think phlogiston has something to do with carbon.

Half the weight of carbon dioxide is 22 g/mol. Is the atomic weight of elemental water 22 g/mol? If we know that water consists of oxygen at 16 g/mol, then the missing half of water weighs 6 g/mol. On the periodic table, it is lithium with an atomic weight of 6.94 g/mol. I'll be honest, I was hoping to see something of carbon here, and not lithium. Ooh, erm... this is awkward.

Not to fear though. It's true, the atomic weight of carbon is given as 12 g/mol, but it's not necessarily always the case. When carbon is measured in compounds where it is present in greater amounts than 12, it is hence always found in multiples of 12. For example, ethane (C2H6) contains 2 carbon atoms at 24 g/mol, and benzene (C6H6) contains 6 carbon atoms at 72 g/mol. The atomic weight of carbon cannot be greater than 12, BUT it is possible that it could be an integral submultiple of 12, such as 6, 4, or 3.

In trying to understand how this is possible, I came across Wikibooks and I chanced upon a really helpful page entitled ~ "Chemical Principles/Are Atoms Real? From Democritus to Dulong and Petit". It's a brief outline of the difficulties faced by pioneering chemists in trying to quantify compounds, to deduce the atomic weight of the periodic table. They did not have an enviable task as the elements they unearthed from compounds are swimming in awkward soups of weight ratios.

I think it gives me a bit of scope in realising the potential for mistakes in working with these ratios. We are, after all, only human. It also gives me a little faith in being able to play around with my own ideas, and to insert some of these ideas into a field as well established as physics, without being overwhelmed by the feeling that I am too small, too inadequate, and too ridiculous. You can find the site here, thanks to:

The site also features a wonderful quote from the German chemist Friedrich Wöhler, whom in 1835 said that "organic chemistry just now is enough to drive one mad. It gives me the impression of a primeval tropical forest, full of the most remarkable things, a monstrous and boundless thicket, with no way to escape, into which one may well dread to enter." After only a little thought so far regarding weight ratios, and the way they richochet and rattle around my brain, I find it easy to sympathise with him. Weight ratios seem to have the ability of swerving any of the applied mathematics you throw at them.

It is possible then that water is made up of carbon and oxygen. I think the reason we don't see carbon when we decompose water is because it is consumed in the reaction. The carbon is used up and leaves nothing but an empty shell in the form of hydrogen.

What happens then to the other half of the carbon dioxide compound? If one half is water - what is the other substance which weighs 22? Well, that could be another water atom. Or, if we refer to the periodic table, that substance might even be sodium. Could carbon dioxide be a compound made up of oxygen, carbon and sodium?

Carbon monoxide (CO) has an atomic weight of 28 g/mol. If we then deduct this new atomic weight of water (22 g/mol), we are left with 6 g/mol. Carbon monoxide could well be made up with water plus an extra dollop of carbon. This would mean that carbon monoxide contained 16 g/mol of oxygen, with a total of 12 g/mol of carbon. In text books, the weight ratio of carbon to oxygen in carbon monoxide is given as 3 to 4, which so far, coincides nicely.

In terms of volume though, 2 mol of carbon are burned in one mol of oxygen to give 2 mol of carbon monoxide. This means carbon monoxide is made up two-thirds carbon and one-third oxygen. If you burn 2 mol of carbon in 2 mol of oxygen you obtain 2 mol of carbon dioxide. The mixture for carbon dioxide is 50/50 oxygen and carbon. Based on this, I think carbon monoxide is more phlogisticated than carbon dioxide.

Science had to explain the weight of carbon dioxide (44 g/mol). They did this by adding an oxygen atom (16 g/mol) to a carbon monoxide molecule (28 g/mol). I think they may have painted over something.

If you decompose 2 mol of carbon dioxide you get 2 mol of carbon monoxide and 1 mol of oxygen. For the oxygen to have become available, I think it may have been part of a water atom. This would suggest that carbon dioxide is a compound made up with 2 water "atoms". In the process of decomposition, one of the atoms is broken down into its two components - oxygen and carbon. The oxygen is given off, but the carbon is absorbed by the other water atom and it becomes carbon monoxide.

I think that the reason that hydrogen is so light is because it contains none, or hardly any, phlogiston. BUT, carbon monoxide (28 g/mol) appears to be lighter than carbon dioxide (44 g/mol) even though it contains a higher volume of carbon. I wonder why carbon dioxide is more dense than carbon monoxide?

I wanted to know the atomic weight of the air. From what I've seen on the web, it appears that most of the time science books only calculate the weight of the air. They use the figures of 79% nitrogen and 20% oxygen which work out to make the atomic weight of air something like 28g/mol. This site illustrates the method for calculating the atomic weight of air beautifully:

I then found a site which carries out an experiment which physically measures the weight of the air. They found that the mass of a litre of air is about 1 g. By volume, one mol of gas represents 22.4 litres at standard conditions. That means that according to this experiment, the atomic weight of air is 22.4 g/mol! That's practically the atomic weight of water - and more specifically - water vapour. You can find this experiment here, thanks to :

The atomic weight of oxygen is nearly 3 times that of the carbon found in water, but in terms of volume, I suspect it is 50/50. Surely the two working together as elemental water thus become indivisible?

How can carbon dioxide at 44 g/mol exist in air that weighs 22.4 g/mol? I'd say that carbon dioxide weighs twice as much as air. Carbon dioxide ain't going anywhere but down and hitting the ground! The following site gives many examples, some catastrophic, of where carbon dioxide has proved heavier than air:

“One of the most serious hazards occurs when volcanoes emit large quantities of carbon dioxide. Carbon dioxide is heavier than air and collects in low spots, displacing air in these locations. Hundreds of people have died of carbon dioxide asphyxiation near volcanoes in the past two decades, most of them in Cameroon, Africa, and in Indonesia.”

Mind, we've all seen how carbon dioxide is collected from a candle as it rises from the flame. How exactly does it get up there if it's twice the weight of air? Carbon dioxide gets a lot of bad press for its ability to climb up high into the atmosphere and mess about as a greenhouse gas. How does it get up there? How does it stay up there?

According to this new theory, the atomic weight of water is almost exactly the same as the air. I think this illustrates that air IS vaporous water. The obvious difference between liquid water and water vapour is density. Liquid water is around 1700 times more dense than water vapour. In other words, liquid water expands some 1700 times to become water vapour.

This suggests that the reason warm air rises is because it has a lower density than the colder air. The reason for this low density could be that the warm air has expanded. Right now, I'm thinking dreamily about bubbles rising in a fizzy carbonated drink. According to atomic weight the carbon dioxide should just sit at the bottom - but it doesn't. The carbon dioxide gas can be quite plainly seen as bubbles which rise up and tickle my nose.

Carbon dioxide is also behind the science of how yeast helps bread to rise. Carbon dioxide expands in the dough to produce gaseous bubbles. So yeast produces carbon dioxide? I would like to thank the following site whose explanation I have borrowed: http://www.nyhallsci.org/biochem/content/educators/bread-educators.pdf.

"A scoop of packaged yeast with a scoop of sugar are mixed in a tube and placed in some warm water. After 2 minutes, bubbles rise from the bottom of the tube as the yeast metabolizes the sugar into carbon dioxide and ethanol. When bread is made the yeast metabolizes the sugars from the flour, and makes carbon dioxide bubbles. These bubbles make the dough rise, and are later seen as the holes in bread.

Cakes rises differently. The chemical reaction between the acid and the base in baking powder, or the reaction between baking soda and an acid, also generates carbon dioxide gas."

Now my mind is thinking about some school experiment, where a raisin is in a glass of coke. The raisin rises to the surface of the drink as it floats on bubbles beneath it. Once it reaches the surface, the bubbles burst, the raisin loses its support, and it falls to the bottom of the glass. The raisin then collects more bubbles which send it floating back up to the surface. My thanks to Steve Spangler Science who have kindly put on a show of the dancing raisins:

I get the feeling this is saying something about how warm air rises and how cold air falls. Warm air expands and rises, and then once it reaches the top, the bubble bursts, it condenses, and it comes back down to earth. What are we describing then - some kind of motor? Are we living in a fizzy drink? Can this in any way be applied to the forces moving through the tubular ring of the atomic torus?

This comes as nothing more than a quirky aside, but for me, the thing that is conspicious about the number 22 is the fact it is not divisible by the numbers 12, 6, 4 or 3. What does this mean? I don't know. Probably nothing. Or it could be important.

There's also a bit of mysticism surrounding the number 22. In numerology, the number 22 is known as the "master builder" and is usually symbolized by a mason or some craftsman working hard and diligently on a large scale project. The Hebrew Aleph-Beit has 22 letters. The Jews believe the letters of the alphabet are the "building blocks" of creation.

Part II to follow.

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