If it is real, then the phenomenon called “Cold Fusion” (or CF) depends, before anything else, on the ability of hydrogen to permeate a volume of solid metal. The proposed experiment derives from a study of certain available information about hydrogen permeation and catalysis. It should also be fairly simple and inexpensive, compared to many other experiments, since mostly lead is to be used, instead of more-difficult elements such as titanium or palladium.
One way to better understand the scope of this particular mystery is to compare hydrogen with helium:
It can plainly be seen from the chart that the helium atom has a smaller radius than a hydrogen atom. It should logically follow that anything hydrogen can permeate, the smaller helium atom should be able to permeate even better. Especially when one considers the fact that often hydrogen occurs in the form of a two-atom molecule (an even bigger object!), and it is this molecule that is normally involved, when hydrogen gas encounters a metal.
Nevertheless, while helium can indeed permeate a number of substances better than hydrogen, when defect-free metals are involved, hydrogen often permeates better than helium. A reference:
Thus there is a mystery, regarding how the relatively larger hydrogen molecule can permeate something that the relatively smaller helium atom cannot. Note that the particular metal involved above is an alloy of the chemical element palladium. This element is one of a group sometimes called “noble metals” (which includes platinum and gold) because they are relatively unreacting with other chemicals. Palladium also happens to be the champion, among pure elemental metals, in its ability to hold hydrogen.
Here is a chart that might offer a clue, towards solving the mystery:
“Electronegativity” is a description of the degree to which one atom can attract an electron from another atom, to form a chemical bond. Hydrogen is near the middle of the range; sometimes its electron is attracted, and sometimes it does the attracting. And while palladium has the same electronegativity as hydrogen, it doesn’t do much of either, attracting or letting go, of electrons. The difference is related to the number of electrons it takes to fill an electron shell. Hydrogen’s electron shell can only accommodate two electrons (and the atom has one of those two); palladium has a shell that can hold eighteen –the shell is divided into “subshells” to accommodate them. Palladium is not only in the middle of the range of electronegativities, it is also, in one sense, in the middle of filling its electron shell; it is “distant” from the places in the Periodic Table where atoms most readily give or take electrons. In another sense, palladium has a completely filled subshell, giving it a bit of similarity to atoms like helium and neon, which have their entire electron shells completely filled, and also have essentially zero ability to chemically react with anything. One very important consequence of this, for palladium, is that unlike most metals, when exposed to air it does not quickly react with oxygen and form upon its surface a thin metal-oxide layer. The electrons at the surface of a piece of palladium metal are not chemically bonded to anything; we can call them “loose”.
Here is a link that’s all about the loose electrons in a piece of metal:
Another data item, either a relevant clue or a red herring, can be found here:
While the linked page has a discussion of the breakdown of carbonic acid into carbon dioxide and water, the way in which it happens involves other water molecules and a process called “catalysis”:
It is interesting that in this particular case the chemical reaction can be catalyzed to go either way, by the same catalyst. That is, when carbon dioxide gas dissolves in water, a fraction of it always reacts with some of the water to make carbonic acid, thanks to other water molecules catalyzing the reaction. An important fact about all of this is that carbon dioxide and water both have high-strength chemical bonds; we burn vast quantities of hydrocarbon (“fossil”) fuels to obtain the energy that is released when those bonds are formed. The fact that those strong bonds can so easily be manipulated by a catalyst needs to be remembered.
Next, since the electrons at the surface of a piece of palladium metal are potentially available to interact with other atoms that encounter that surface, it is observed that palladium is a good catalyst for a great many chemical reactions. Also, the chemical bond between the atoms of a hydrogen molecule is middling-strength. Finally, at ordinary temperatures, hydrogen gas molecules move about at a fairly high speed (roughly 10 kilometers per second) and consequently possess significant kinetic energy. Let us now add all the data/clues together, and entertain the notion that when a hydrogen molecule encounters some palladium metal, it might fall apart. Completely. The kinetic energy of its motion, catalyzed, suffices to break the molecular bond. Since their speed was used up to do that, the hydrogen atoms are now moving relatively slowly among palladium atoms, and their individual electrons are ready to interact with palladium electrons –except that both elements have the same electronegativity! If we were to speak in terms of “preferences”, we could now wonder, “Why would a hydrogen nucleus prefer its own original electron to any of the loose electrons in the conduction band of the palladium?” As far as it is concerned, any of those loose electrons might as well be its own electron!
We might therefore conclude that the hydrogen atoms start completely sharing their electrons with electrons in the conduction band of the palladium. This process, when it happens between metals, is called “alloying”. We have good evidence that hydrogen is able to exist as both a metal and as an alloy:
In this situation the result is, with its one-and-only electron gone, having joined the conduction band, that the hydrogen nucleus now has no electron shell at all in the conventional sense. It is now a bare nucleus, which happens to be about 1/100,000 the size of the atom. Lots smaller than helium! And ready to permeate that piece of palladium almost as easily as if the metal wasn’t even there.
To the extent that something like that can happen between hydrogen and other metals, this may fully explain the generic permeation mystery. Helium, of course, hangs onto its own electrons too tightly for it to do anything like the alloying trick, and so the atom remains too big to permeate. For metals that have a small hydrogen permeation rate, reasons why can obviously take different electronegativities into account, but perhaps the biggest reason is that most metals react with oxygen in the air, and actually have very few loose electrons at their surfaces. A hydrogen molecule would have to, as a whole, physically penetrate the oxide coating on the surface of the metal, before it could interact with any loose electrons and break apart and alloy itself with the metal. Most of the time the oxide coating is simply not penetrable enough, by hydrogen molecules.
We might now use this information to perform a Cold Fusion experiment. One of these days, someone will perform a CF experiment that leaves no doubt, in any skeptic’s mind, regarding whether or not something unusual is in fact happening. Perhaps this can be that experiment?
Let’s start with a thick-walled glass container, since hydrogen does not permeate glass very well at all. We want this container to somewhat resemble a laboratory flask, such that it has a “neck”. We take this flask to a chamber where the atmosphere is pure nitrogen, instead of ordinary air. We fill it with molten lead, a relatively inexpensive metal, most of the way up the neck, and allow the lead to cool. Part of the reason we want the container to have thick glass walls is so that it can handle the heat without breaking.
While cooling, the lead shrinks a bit in volume. We may have to pour the molten lead in stages, to ensure that the metal, when cooled, fully contacts the glass. We also want to be sure that the only surface area available, for the lead to interact with gas later on, is the part that occupies the neck of the glass container. Upon becoming cool, we move the container from the nitrogen-filled chamber to a vacuum chamber. In this way we ensure that no oxide coating spontaneously forms on the exposed lead surface (and nitrogen is non-reactive enough to have ignored the lead).
Inside the vacuum chamber we apply a technique known as Chemical Vapor Deposition:
Basically, we just want to apply a thin coating of palladium over the exposed lead surface, inside the neck of the glass container. When completely done, we have completely “sealed” the lead, so that no part of it can react with atmospheric oxygen at any point in the future. We will also have used only a very small amount of palladium, which is important in the sense that if CF is real, then palladium is simply too rare and expensive to use it for that purpose on a large scale. It will be necessary to build CF reactors that use as little of the element as possible. And so, inside the neck of this glass container, the surface area of the exposed lead, that we wish to coat with palladium, might be just one square centimeter, or even smaller.
Next, we take the container and hook it up to a source of pressurized deuterium gas. Deuterium is a variety of hydrogen; it chemically reacts with other substances very much like ordinary hydrogen:
According to the data assembled earlier, we should expect deuterium molecules to break apart, and their nuclei will permeate the thin layer of palladium. On the other side, they will encounter the first part of a significant volume of lead. Will they continue to permeate, or will they grab electrons and become whole atoms/molecules once again? The table of electronegativities linked earlier indicates that lead has a slightly tighter grip on electrons than hydrogen (indeed, that is a significant reason why lead was chosen for this experiment). We should be able to conclude that the deuterium nuclei will continue to permeate metal, all the way until it reaches the thick glass walls of the container. Glass is a good electrical insulator, so while the conduction bands of palladium and lead will intermingle freely, they will stop cold at the glass. Any deuterium nuclei that try to permeate into the glass would be leaving their electrons behind, and the electrical attraction between those electrons and those deuterons should therefore prevent any significant permeation. To the extent that deuterium gas does try to form at the interface between the lead and the glass, well, one other and very important reason why we want the container to have thick walls is, we want it to withstand the pressure that will be applied to it from within, as the gas that has permeated the metal tries to get out again.
The whole idea here is that we can try to pressurize deuterium into the lead-filled glass container until Cold Fusion happens. If it can happen, of course. There would be an increase in the temperature of the container, and an increase of the pressure against the deuterium gas supply, which should be measurable.
Added March 3, 2009
Perhaps it should previously have been mentioned that Cold Fusion researchers have concluded that the quantity of deuterium atoms that permeate a piece of metal (“loaded” into it) needs to approach the total number of metal atoms in the metal, before one might expect to see evidence that Cold Fusion can happen. Depending on what source-material is examined, figures such as 80% loading, 85% loading, or even 90% loading may be specified. CF researchers are quite convinced that the difficulty of achieving sufficient loading explains most of the early failures of experiments that involved the electrolysis of heavy water. In this particular experiment, only the ability of the container to resist pressure should limit the amount of deuterium that can be loaded into the lead. Obviously, therefore, the thicker the container walls, the better.
Some additional information has recently been encountered by the author, which may make it worthwhile to recommend a modification to this experiment.
This page indicates that a Cold Fusion system should not be in thermodynamic equilibrium (it shouldn’t just “sit there”).
This page indicates that the presence of a significant electric current may be beneficial in promoting Cold Fusion. If we combine this with the other data, we might conclude that a changing electric current can both easily exceed the minimum specified value of 280 milliamperes per square centimeter, and also qualify as a non-equilibrium situation.
Let us now consider a torus-shape (donut-shape) for the poured molten lead. Thick glass still needs to immediately surround the lead, so that gas can be pressured into the cooled metal. A torus can be part of an electric transformer, and an electric current can be induced to flow in the torus. The thick glass container doubles as an electric insulator, between the lead and the surrounding transformer metal (and the other coils needed to create a magnetic field in body of the transformer). The torus itself qualifies as a “single-turn coil”, quite a few amperes can be induced to flow in it (it would be the “secondary” coil of the transformer). The nature of an electric transformer is that it requires a changing flow of electricity to work; ordinary Alternating Current from a wall outlet can be perfect if the primary coils of the transformer have sufficient resistance and/or inductance. A changing flow of current in the lead torus will be the result, exactly as specified in the previous paragraph.