Tuesday, 29 September 2009

Is Hydrogen Empty?

Something is troubling me about hydrogen. Phlogiston theory appears to suggest that hydrogen, or "inflammable air", is full of phlogiston. The way I've worked with the theory so far is that hydrogen is made-up in the same way as nitrogen, or "phlogisticated air". I've so far imagined hydrogen as a big bloated bag of phlogiston - but is it?

Phlogisticated air was common air which had drawn the phlogiston from burning substances. Phlogisticated air no longer had any attraction for phlogiston, or any power in supporting combustion. Air, according to the theory, was merely the receptacle for phlogiston.

After a series of experiments, Cavendish had made the deduction that "phlogisticated air appears to be nothing else than the nitrous acid united to phlogiston". He goes on to say that "nitrogen is nothing else than the nitric acid deprived of oxygen."

Nitric acid (HNO3), also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid that can cause severe burns. If we are to follow Cavendish's line of reasoning, then nitrogen is actually a compound of hydrogen and nitrogen, which if you think about it, is a little odd. It's saying that nitrogen is not simply nitrogen, but is also hydrogen.

Critics of the hydrogen economy are quick to point out that hydrogen is not an energy source, but rather an energy carrier. Hydrogen can store and deliver usable energy, but it doesn't typically exist by itself in nature; it must be produced from compounds that contain it.

I think hydrogen acts something like an anticyclonic weather system. Anticyclonic weather systems are high pressure systems. I also think hydrogen acts a bit like a bag for phlogiston. Hydrogen is therefore not phlogiston per se, but something phlogiston can be found in. So, what we percieve as the element nitrogen is actually a substance stuffed inside hydrogen. I think that substance could be vapourized carbon (phlogiston).

There already exists a compound made of hydrogen and nitrogen, and it is called ammonia. In industry, ammonia is synthesized by heating the reaction of hydrogen gas and nitrogen gas over a catalyst at high temperatures, in a process known as the Haber-Bosch process. The most important use of ammonia is in the synthesis of nitric acid, an ingredient in fertilizers and explosives.

Our bodies also make ammonia. Most ammonia in the body forms when protein is broken down by bacteria in the intestines. The liver normally converts ammonia into urea, which is then eliminated in urine. Ammonia levels in the blood rise when the liver is not able to convert ammonia to urea. This may be caused by cirrhosis or severe hepatitis.

I wanted to return to the experiment where a burning candle stands in a dish of water. When we burn the candle and then place a glass shade over it - phlogiston theory dictates that the burning phlogiston saturates the air inside the glass, which leaves no further place for more phlogiston to escape to, and so the flame goes out (this differs greatly from current theory which maintains that the flame is extinguished because it runs out of oxygen).

When the flame is extinguished, water condenses inside the glass and it pulls a vacuum - water is sucked up from the dish and up into the space underneath the glass. Something like 20% of the space inside the glass is taken-up by the water. In this experiment we find the other 79% of the air trapped under the glass is nitrogen, and 1% other gases (including CO).

Phlogiston theory maintains that the nitrogen present in the air inside the glass is air that has been saturated with phlogiston. Nitrogen was referred to as "phlogisticated air". Nitrogen is air that is full to capacity with vapourized carbon. Nitrogen will not support combustion. I don't think that because the air inside the glass is found to be 79% nitrogen, this means that the atmosphere is also 79% nitrogen. Maybe it's not quite that simple.

Another place where nitrogen turns up is in the composition and decomposition of water with an electric spark. In the reaction of oxygen with hydrogen it is not as simple as saying that they make water. In some cases it is not pure water, but a nitrous acid which is produced. Nitrous acid (molecular formula HNO2) is a weak and monobasic acid known only in solution and in the form of nitrite salts. Nitrous acid readily absorbs oxygen from the air and is converted into nitric acid. Nitric acid is highly corrosive.

I have been haunted by the following words of Priestley. They are taken from his article “Considerations on the Doctrine of Phlogiston, and the Decomposition of Water” of 1796, and can be found here thanks to:

"When dephlogisticated [oxygen] and inflammable air [hydrogen], in the proportion of a little more than one measure of the former to two of the latter, both so pure as to contain no sensible quantity of phlogisticated air [nitrogen], are inclosed in a glass or copper vessel, and decomposed by taking an electric spark in it, a highly phlogisticated nitrous acid is instantly produced; and the purer the airs are, the stronger is the acid found to be."

Priestley asserts that a "highly phlogisticated nitrous acid" is present. What is Priestley trying to say exactly? What has phlogiston got to do with the acidifying principle? Into this soup I shall add some words of Cavendish on the composition and decomposition of water, taken from his treatise of 1785, "Philosophical Transactions" :

"It may be worth remarking, that whereas in the detonation of nitre with inflammable substances, the acid unites to phlogiston, and forms phlogisticated air, in these experiments the reverse of this process was carried on; namely, the phlogisticated air united to the dephlogisticated, which is equivalent to being deprived of its phlogiston, and was reduced to nitrous acid.

In the above-mentioned paper I also gave my reasons for thinking that the small quantity of nitrous acid, produced by the explosion of dephlogisticated and inflammable air, proceeded from a portion of phlogisticated air mixed with the dephlogisticated, which I supposed was deprived of its phlogiston, and turned into nitrous acid, by the action of the dephlogisticated air on it, assisted by the heat of the explosion."

Cavendish states that the phlogisticated air is turned into nitrous acid by the action of the dephlogisticated air upon it. In other words, nitrogen is turned into nitrous acid by the action of oxygen in a heated reaction. It's a bit like the nitrogen was cracked open by the oxygen, and in doing so, phlogiston spills out to fuel the combustion. Cavendish continues to say that "it is evident that dephlogisticated air is able to deprive phlogisticated air of its phlogiston, and reduce it into acid, when assisted by the electric spark; and therefore it is not extraordinary that it should do so when assisted by the heat of the explosion."

If we follow this line of reasoning, then it appears an acid is produced due to the lack of phlogiston. If more phlogiston was available, then we would have a sample which was more like pure water. Priestley seems to confirm this by noting that the "purer the airs are, the stronger the acid is found to be". Priestley thus continues to piece these results together:

"If phlogisticated air be purposely introduced into this mixture of dephlogisticated and inflammable air, it is not affected by the process, though, when there is a considerable deficiency of inflammable air, the dephlogisticated air, for want of it, will unite with the phlogisticated air, and, as in Mr. Cavendish’s experiment, form the same acid. But since both kinds of air, viz. the inflammable and the phlogisticated, contribute to form the same acid, they must contain the same principle, viz. phlogiston."

Now I think at last I am starting to get a grasp. I think this confirms that pure hydrogen gas does not contain phlogiston. I think that once hydrogen becomes "phlogisticated" it starts to resemble nitrogen. Nitrogen without phlogiston is hydrogen. Hydrogen over-saturated with phlogiston is nitrogen.

Electrolysis of water is the decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) due to an electric current being passed through the water. In a properly designed cell hydrogen will appear at the cathode, and oxygen will appear at the anode. I think the electric current passing through the water is made up from phlogiston in the water.

I have experimented with the idea that phlogiston is taken up by the anode, moves along conductors, passes through the battery, and then goes down the cathode where it then completes a loop by passing back through the water to the anode. I think that energy from the loop is lost in the form of heat, or in other words, phlogiston is lost in the form of heat. I think you run out of electric current when you run out of phlogiston. The electric current IS phlogiston.

I think hydrogen is produced at the cathode because the phlogiston it once possessed as one half of elemental water has been given up to supply the current. It's as if the hydrogen has been discarded as a waste product. If hydrogen is a waste product, then what exactly was it when it was previously in water? If hydrogen was phlogisticated while in water, then it is highly suggestive that it is not hydrogen in pure water, but something that is phlogisticated, something like nitrogen.

When hydrogen gas and oxygen gas are recombined to make water, I think that phlogiston is released by the spark or flame used to drive the reaction. If enough phlogiston is available we get pure water, if not, then we get nitrous acid. I found the following words of Cavendish, and his experiments appear to confirm what I am suggesting.

Cavendish states "that when a mixture of inflammable and dephlogisticated air is exploded, in such proportions that the burnt air [nitrogen] is not much phlogisticated, the condensed liquor contains a little acid which is always of the nitrous kind, whatever substance the dephlogisticated air is procured from; but if the proportion be such that the burnt air is almost entirely phlogisticated, the condensed liquor is not at all acid, but seems pure water, without any addition whatever."

In another experiment he writes "that when inflammable and common air are exploded in a proper proportion, almost all the inflammable air, and near one-fifth the common air, lose their elasticity and are condensed into dew. And by this experiment it appears that this dew is plain water, and consequently that almost all the inflammable air is turned into pure water".

When hydrogen is burnt in a combustion engine in the presence of air, water is the only product given off. There's obviously phlogiston present in the air - but is it in the proportions that we have been led to expect? Nitrogen is "air" (or at least a component of air) which has been over-saturated with phlogiston. Maybe we can expect to find 79% of the air in a glass to be nitrogen after the combustion of a candle, but perhaps the air we breath is a little less saturated with phlogiston.

Many thanks:

The Gases of the Atmosphere - The History of Their Discovery By William Ramsay
Chemistry for Beginners By Lincoln Phelps
Researches on the medical properties and applications of nitrous oxide ... By George Jacob Ziegler

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