Some general considerations on using HCl as I'm doing. Most of these are probably obvious, but here they are.
- pH is the negative base 10 logarithm of the molar concentration of hydrogen ions per liter of solution (Wikipedia).
- A pH value of 7 means that the solution has a concentration of 10-7 moles of hydrogen per liter.
- A pH value of 1 means that the solution has a concentration of 0.1 moles of hydrogen per liter.
- A 0.1M aqueous HCl solution, which can be assumed as a strong acid to get fully ionized in water, can be calculated to have a pH of -log10 (molarity) => -log10(0.1) => 1 (Source. Also see Wolfram Alpha).
- Hydrogen has a density at STP of 0.08988 g/L (Wikipedia), or about the same value in mol/L, or very roughly 0.1 mol/L.
- Therefore an acidic solution having a pH of 1 has a hydrogen ion concentration roughly equivalent to that of a gaseous environment with hydrogen at STP.
- Note however that in a gaseous environment hydrogen will be in a molecular form, not ionized.
- In my latest "Unconventional Electrolysis" experiments I have used about 10 ml of water, into which I add some amounts of 10% HCl solution.
- In a test I determined that roughly 0.25-0.30g of 10% HCl can be added, which should very roughly mean 0.025-0.030g 100% HCl.
- HCl has a molar mass of 36.46g/mol. 0.025g HCl is roughly 0.0007 mol of HCl.
- 0.0007 mol / 10 ml means 0.07 mol/L which is close to a 0.1M HCl solution.
- Therefore the pH of the solution I routinely use should be close to 1, almost equivalent to having a gaseous environment at STP composed of fully ionized hydrogen.
- This excludes hydrogen evolved or removed with electrolysis.
Is there anything significantly wrong with this reasoning? Regardless of electrodeposition processes easily promoting arc discharges in these experiments, an acidic electrolyte seems like would be a desirable thing in general and indeed, hydrogen embrittlement is sometimes reported to be occurring in such environments. In most electrolytic cold fusion experiments an alkaline electrolyte is used instead.
Definition - What does Acid Embrittlement mean?
Acid embrittlement is a process in which brittleness is induced in metals, especially steel, when immersed in acidic solutions. Acids contain hydrogen, and when these metals are immersed in acids, they absorb hydrogen, becoming brittle, and can readily fracture when subjected to stress. [...]
EDIT: after a search on LENR-CANR.org it appears that Francesco Celani's group also used HCl as an electrolyte (in various concentrations, but always keeping pH in the 4.5-5.5 range) in some of their early 2000s standard electrolytic experiments.