I am new to chemistry, having gone down an electronics route in my career, so I decided to pick up where my 'O' levels ended (many years ago) and make a better understanding of the topic a sort of hobby.
As it seems it's almost impossible, at least as an individual, to obtain strong acids in this country. I am forced to create my own....
The research I've done so far pointed me to the Berkland-Eyde Process, being a means to directly synthesise Nitric Acid from air and being 'safer', with less also hard to obtain ingredients, than most other methods.
I built a Berkland-Eyde apparatus, and in about 8 hours managed to create a rather paltry yield of 250ml of 6% concentration HNO3. Which I could concentrate to ~60-70% through distillation, though that would be a very small yield for a rather large effort in time and equipment.
I notice that articles on this use significantly larger currents (I am limited to just 20mA at 10kV without spending a lot on a more powerful PSU)
I came here to search for answers and was surprised to find this question or anything like it does not exist - so here it is!
I could try to obtain an old style Neon sign transformer, but they are rare. Modern powerful ones are very expensive and I am looking for a cheap solution, i.e. This is just for self education and not worth investing in.
I have found a cheap 600W/50kV/DC (adjustable) PSU, huge compared to my current 200W (probably less) 20mA/10kV/400Hz/AC one (which is not happy about what I am asking of it, as it gets hot and is starting to arc internally).
Other options I have found:
- Diesel/Oil heater ignitors (electronic) or (iron)
- CO2 laser PSUs, like or
- Cheap, crude 'ZVT' fly-back transformer based PSUs
- Old school transformer based Neon sign PSUs
- Modern lower current electronic Neon sign PSUs (one issue here is that they often are USA mains, so 110V, the mains here is 230V).
Firstly, and the main purpose of this question:
- Would using DC rather than AC make a significant difference?
There are some other related questions (perhaps I should write more than one question?):
From a physics and chemistry perspective what attributes optimise the result, e.g. Any combinations of:
- Area of air flow vs arc
- Arc length
- Electrode shape
- Duty cycle (big regular pulses vs smaller contiguous arc)
- Electrode temperature
- Flow rate
- Additional attributes, e.g. Presence of magnetic field
What is the best 'balance' between voltage and current? Is it the hot electrode or the gas plasma that does the work? I ask this as the PSU is adjustable so at a lower voltage I can have more current (within limits).
A higher voltage means a longer (or hotter) arc. Would constraining the air path and forcing it past the electrodes be better than slowing the air down to have it spend longer in the reactor?
My current electrode are Tungsten TIG welding rods, which seem to work and I don't get any noticeable discolouration of the product, but:
I have been advised that the red hot Tungsten reacts with the small quantity of acid present in the reactor due to water vapour being pulled in. This is true and what should be used instead. I first tried copper but it immediately melted.
Is there any data on the rate of generation I should expect for a given air flow rate and voltage?
UPDATE: I read up on the current state of law and found that I was given incorrect information. Now a license for certain substances can be obtained by individuals rather than just corporate entities. In searching for this I also found a list of other controlled chemicals, to which I linked for completeness.
Substances on that list now require a license to possess (costing £40 and lasting 3 years) this is now to control (rather than prevent purchase as was the original intent from 2014) as a non-corporate entity - so actually an improvement!!