Sodium Nitrite

If no luck elsewhere (and in no hurry) you might try adapting the time honoured 'saltpeter from urine' approach. Involves a pit. straw, chicken poo and urine and time. I seem to remember the result was boiled up and stewed with wood ash (potassium carbonate). Easy to substitute sodium carbonate (washing soda). The result is usually a mix of nitrate and nitrites. Best to wait till SWMBO is out....

Recall reading in some medieval gun history revival of some Dutch folk trying this out, the results a bit disappointing though. Perhaps some good English pee will do the trick. Other recipes are available.

Michael i can let you have some for the price of 1st class postage or first class signed for. Dont know how much there is probably around 20-40 gms (i`ll check now).Send me a pm if you`re interested.

update i can spare 50 gms, 10 gms lasts me ages ,i use it for darkening raw violin wood before varnishing.The bag at the top of the photo weighs 53 gms.

Edited By mark smith 20 on 25/05/2020 15:31:25

Edited By mark smith 20 on 25/05/2020 15:35:03

P.M. sent, Mark

... Much appreciated !!

MichaelG.

With enormous thanks to Mark ... I tried my first experiment today

It was, predictably enough, a failure :

The wire that I currently have to hand is only about 50 microns diameter.

This is much too fine to make a probe/needle because I cannot straighten it; and it is not sufficiently stiff to perform the ‘chemical sharpening’ process.

I will update this when I have some thicker wire.

MichaelG.

Thanks to three generous donors, I now have wire of approximately 20, 50, 75 and 500 micron diameters to experiment with.

Unfortunately, this is proving trickier than I anticipated

20 and 50 micron wires are too thin to be 'self supporting' at the lengths required for my probes

75 micron may be the minimum useable diameter, and 500 micron is my maximum

Today, I tried the process shown in the video, and failed completely

... No exothermic reaction, and no sharpening.

Further reading suggests that [although a cold dip is specified by some], it is better to have the Sodium Nitrite molten, at least locally. [*]

There will now be a pause whilst I consider the options.

MichaelG.

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[*] **LINK**

https://books.google.co.uk/books?id=V0oEzMp7axAC&pg=PA107&dq=sodium+nitrite+stick,+tungsten&hl=en&sa=X&ved=0ahUKEwi-m_jUuevpAhVNY8AKHZRSB6sQ6AEIJzAA#v=onepage&q&f=false

https://youtu.be/WvepYAwiKU8

Edited By Michael Gilligan on 05/06/2020 22:07:18

This appears to be the original description of the electrolytic method: **LINK**

https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC2555190&blobtype=pdf

MichaelG.

Out here I can only get it from an industrial chemical supply place, and have to have a current chemical handlers licence to purchase and use.

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Thanks for the info. Neil

To be clear ... I now have about 50g of ‘food grade’ Sodium Nitrite, which is probably all I will ever need.

What does continue to astonish me is the ‘duplicity’ involved in the supply and use of this chemical.

The MSDS describes its hazards in chilling detail, and yet

1. Philip Harris [et al] sell it to schools in 250g containers
2. It continues to be used in food preparation
3. It is the major constituent of ‘Chem Sharp’ **LINK**

MichaelG.

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Edit: Here’s a typical MSDS: 

https://www.fishersci.com/store/msds?partNumber=S25560A&productDescription=SODIUM+NITRITE+GRN+500G+RG&vendorId=VN00115888&countryCode=US&language=en

Edited By Michael Gilligan on 06/06/2020 10:18:30

The electrolytic method is worth a try because it only needs Sodium Hydroxide (Caustic Soda).

Having the Sodium Nitrite in stick form may be important. The video lady draws and twirls the red hot tungsten needle across a solid lump of Nitrite held just inside the flame. I suspect the diameter of the stick matters as well as the solidity of the chemical. The stick is probably made by casting molten Sodium Nitrate, requiring careful temperature control, and is high-density compared with loose crystals.

I found a US site selling Nitrite Sticks. No idea what would happen if a genuine UK microscopist innocently ordered one, or if the seller exports! Perhaps a US member could obtain and post privately. If you end up in jail, I'll start a 'Free the Gilligan One' campaign.

I find it annoying when my microscopy books assume I have a well-equipped University laboratory! Boiling Oleum - no problem...

Dave

Thanks, Dave

The seller you found is McCrone ... who you might recognise as the employer of the lady in the video, and as the author of the book that I referenced.

The stick is manufactured by Sigma-Aldrich ... whose MSDS is linked on the McCrone page.

S-A has some pretty stringent [and pricey] shipping arrangements.

In case you hadn’t guessed ... my journey started with the Hooke College video.

Great investigative powers though, Dave

MichaelG.

It's a shame people abuse chemicals. I understand why Sodium Nitrite is controlled but a mad bomber would need hundreds of those sticks, whereas just one would keep a busy tungsten sharpener like yourself happy for years!

As for postal charges from the USA, ouch.

Dave

Forgive me if this is granny suck eggs time.

Google STM tip preparation, I found what looked a credible approach at Zeljkovic Lab

Basically an electrolytic etcher with some fancy electronics to cut the etch current.

I seem to remember doing the etching with the tungsten inside a plastic tube hanging in the usual NaOH or KOH type electrolyte.

Some advise a loop of s/steel wire as the other electrode - presumably to shape the current density gradient.

Any and all advice is welcome, Roger

I fancied trying the Sodium Nitrite approach because it’s quicker and takes up less room

[supposedly]

I will follow-up your Zeljkovic ‘lead’ this evening; but meanwhile could you let me know what size of points you were working with ?

For what I want, this seems to be the ‘defining’ article about electrolytic sharpening: **LINK**

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2555190/pdf/bullwho00274-0151.pdf

... but I’m sure some modern current-control circuitry would improve things, and perhaps even a stepper motor to control the dipping [cue massive scope-creep]

Thanks

MichaelG.

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Edit: I have chores to do, but couldn’t resist a quick look:

https://capricorn.bc.edu/wp/zeljkoviclab/research/scanning-tunneling-microscopy-stm/stm-tip-preparation/

Edited By Michael Gilligan on 06/06/2020 16:09:35

I am afraid I have never used this technique. I looked into making an STM some time back and remembered the technique.

The nearest I have come to making needles is the watchmaker technique of:-

fit brass wire in pin chuck

pull out bench drawer and file shallow groove in top edge

lay wire in groove

file and twiddle to get long thin point, use very fine file at end

You 'LINK' technique looks like it should work and from a credible source - and simple too. Good luck.

Suitably encouraged by the ‘kitchen sink’ set-up shown on the Zeljkovic Lab page ... I read the closing paragraph and realised that their needle points are at least an order of magnitude sharper than I need, and come with some significant ‘overheads’

MichaelG.

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[quote]

Regardless of the storage method, STM tips must be cleaned before use. One way to do this is to submerge the tips in hydrofluoric acid, which removes any contamination or oxide layer on the tip. Subsequently, the tips are also annealed at high-temperature in ultra-high vacuum to remove any remnant oxide layer, before they are inserted into the STM head and used for measurements. Radius of tip curvature achieved with the setup described above was less than 50 nm.

[/quote]

Success

I put a pinch of the Sodium Nitrite in the bowl of a Stainless Steel tablespoon, and melted it with over the cook's blowtorch. Then heated the wire to bright red, positioned close the puddle.

Exothermic reaction took the wire to near white hot, and I twiddled the wire twixt thumb and forefinger whilst withdrawing it from the molten Sodium Nitrite.

Here's a quick photo of the resulting point, alongside another piece of the same 0.5mm diameter wire.

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Many thanks to Jason for the 0.5mm 'Green' [i.e. pure Tungsten] TIG welding electrode.

Clearly, my technique needs refining ... but the principle is proven

.

MichaelG.

PostScript:

Tried the 75micron [0.003”] wire that Edwin kindly provided. < Thank You >

The sharpening process works, but my rough handling produced a bent tip

As mentioned on 05-June This is probably the minimum useable diameter of wire for manual tools

... It is [obviously] significantly stiffer than the 20 and 50 micron wires.

MichaelG.

Making a Sodium Nitrite ‘stick’ turned out to be easier than I dared hope.

I found a short length of stainless steel tube, and a cork from a Sherry bottle which fit nicely.

... Melted the crystals and poured the liquid in !!

Adhesion to the cork was good, and to the tube was weak.

Using the 0.5mm TIG electrodes works very well ... red hot wire in a small puddle of molten Sodium Nitrite starts the exothermic reaction, and the rest is just down to technique. [still have some work to do there, but I know the principles].

Thanks to all those who assisted

MichaelG.

Well done Michael!

Hi Gents,

I have just seen this thread and see the situation is now resolved. However it may be worth my noting that a good source of sensibly priced chemicals is available from:

apc pure, find them on line, 0161 351 9599

I use them for my salt bath annealer.