What's the scope of an Element Transmuter?

Question

Scenario:

• When one thinks of elemental transmuters from mythology or comic books, one thinks of single touch by the transmuter to a large, multi-elemental structure (like a human body) that causes cascading changes across a wide variety of elements, resulting in a complete conversion to a totally new material, targeted by the transmuter, irregardless of whatever the source materials used to be.

• However, the more "practical" view of an element transmuter is that he/she is only able to flip a few ounces of a single element into a different element, based upon familiarity with both the source material and the final result. This enforces severe limits to what the operator can do, and the scope of the consequences. A Bachelor's Degree in Chemistry would be extremely useful to such an operator.

• The details of the character in question are irrelevant at this point, other than he/she was researching the Biological Transmutation Theory of Corentin Louis Kervran (see here, here, here, and here), notably the transmution of sodium to potassium within the human body.

• Sodium and potassium are essential electrolytes, a dietary requirement for us humans. Sodium helps regulate the amount of water that's in and around your cells. A 50 kg person would contain around 200 grams of sodium chloride – around 40 teaspoons. It plays a key role in many functions, from the quality of blood to transmission of nerve signals. Potassium protects the heart and arteries, and may even prevent cardiovascular disease. The total quantity of potassium in the human body lies somewhere between 110 and 140 grams, and while most of it lies in the red blood cells and brain tissue, its final value depends upon muscle mass. It serves mainly as a nerve stimulus, in muscle contractions, blood pressure regulation, and protein dissolution. But, sodium and potassium can only operate within a narrow range of values. Outside of that range, they both turns into nasty, caustic agents.

• It was during the aforementioned research that the character discovered that he/she could replicate transmution of sodium to potassium on a macro scale (again, the mechanics are irrelevant at this point)...which induces sudden, severe, simultaneous Hyponatremia (sodium starvation) and Hyperkalemia (potassium poisoning) – bringing about rapid brain swelling, paralysis, and/or heart failure in the subject.

Note: while this process could be extremely useful in a life-or-death fight, it's rather mundane in nature for someone with superpowers.

So, here's my question: could this process lead to other, somewhat more spectacular methods of offense/defense?

For instance, potassium reacts rapidly and intensely with water (an exothermal reaction which heats it to such an extent that it burns a purple flame), forming both a colorless basic potassium hydroxide solution, and hydrogen gas (which reacts strongly with oxygen and ignites). Sodium also reacts quickly with water, to produce sodium hydroxide and hydrogen gas. And since 60% of the human body is water...could this volatile reaction lead to something approximating Spontaneous Human Combustion?

Answer 1

This person would be an omega level mutant in the Marvel Comics scale.

This is what non-crackpots say about Kervran's work:

In the 1960s, Louis Kervran claimed to have conducted experiments and studies demonstrating violations of the law of conservation of mass by biological systems, according to which the amount of each chemical element is preserved in all chemical reactions. Specifically he claimed that organisms can transmute potassium into calcium by nuclear fusion in the course of making an egg shell (...)

Let that sink for a moment, specifically the part where it says:

nuclear fusion

This is the proccess that powers stars. It generates more power per mass than atomic fission. If the character can do that with impunity, then even just a few grams of salt are enough to level a small town.

Fusing hydeogen to make a single gram of deuterium releases 10¹² joules. A back of napkin calculation puts that into the proximity of a 2,100 or more tons of TNT blast. And that's just adding one humble nucleon to hydrogen. Going from Sodium into Potassium requires eight protons and some neutrons to go with them.

You know, at this point I believe Kervran's igNobel winning theory could be the pseudo-scientific explanation for the powers of the villain that started the whole Civil War saga, Nitro:

As a result of genetic re-engineering by the Kree, Nitro can transform his body into a gaseous state and explode with a maximum force equivalent to 350 lb (160 kg) of TNT - which can however be multiplied under influence of MGH - and reconstitute himself.

(...) could this volatile reaction lead to something approximating Spontaneous Human Combustion?

Given what the character can do, spontaneous combustion is the least of your worries. They've got to be able to reassemble themselves to survive anyway.