Sodium Nitrite

[Michael GilliganParticipant @michaelgilligan61133]

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.

.

[*] **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

[Michael GilliganParticipant @michaelgilligan61133]

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

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

MichaelG.

[Neil LickfoldParticipant @neillickfold44316]

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.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Lickfold on 06/06/2020 09:17:00:

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.

.

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.

.

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

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 05/06/2020 23:05:17:

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

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

MichaelG.

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

[Michael GilliganParticipant @michaelgilligan61133]

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.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 06/06/2020 10:54:04:

…

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

…

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

[Roger HartParticipant @rogerhart88496]

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.

[Michael GilliganParticipant @michaelgilligan61133]

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.

.

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

[Roger HartParticipant @rogerhart88496]

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.

[Michael GilliganParticipant @michaelgilligan61133]

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.

.

[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]

[Michael GilliganParticipant @michaelgilligan61133]

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.

.

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.

[Michael GilliganParticipant @michaelgilligan61133]

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.

[Michael GilliganParticipant @michaelgilligan61133]

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.

[Neil WyattModerator @neilwyatt]

Well done Michael!

[JagerParticipant @jager]

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.

[Oily RagParticipant @oilyrag]

On the topic of Sodium Nitrite if you know someone with an early 1950's Field Marshal tractor they use a 'saltpetre' paper wick to start the single cylinder 5.5litre 2 stroke diesel engine. Nowadays they have to make a box of wicks up as they are not available any longer from Mattersons! Hard work cranking that engine over if you haven't got a 12 bore blank cartridge handy!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Jager on 18/06/2020 20:14:05:

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.

.

Thanks for that

With an 0161 number, they can’t be a million miles from me.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Oily Rag on 18/06/2020 20:26:32:

On the topic of Sodium Nitrite if you know someone with an early 1950's Field Marshal tractor they use a 'saltpetre' paper wick to start the single cylinder 5.5litre 2 stroke diesel engine. Nowadays they have to make a box of wicks up as they are not available any longer from Mattersons! Hard work cranking that engine over if you haven't got a 12 bore blank cartridge handy!

.

Intriguing !! … 

Unfortunately though [unless, of course, you know better] Sodium Nitrite is one of the few variants on the theme which is not known as saltpetre.

https://en.wikipedia.org/wiki/Saltpeter_(disambiguation)

The exothermic reaction with Tungsten seems to be very specific.

Do please correct me if I am wrong … I am a tinkerer, not a chemist !

MichaelG.

Edited By Michael Gilligan on 18/06/2020 20:56:48

Edited By Michael Gilligan on 18/06/2020 20:58:04

[Oily RagParticipant @oilyrag]

Micheal, you are absolutely correct, my mistake – getting my -ites and -ates mixed up! It is interesting to read how many compounds of alkali salts are listed as 'saltpetre' – Sodium, Calcium and Potassium. All very confusing, especially the reference to food processing. Which is where the connection with cured bacon, butchers, and farmers comes from!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Oily Rag on 19/06/2020 09:45:02:

.

– getting my -ites and -ates mixed up!

.

Very easily done

… but many thanks for the interesting note about engine starting

MichaelG.

[Phil PParticipant @philp]

The Field Marshall comments bring back happy memories of when we had a couple of those tractors.

We always used to start ours on the handle, they have a very simple de-compressor mechanism to allow you to crank it easier, there is a threaded groove on the outside of the flywheel into which a roller lever engages to pull a cable that opens the de-compressor valve. you have to be carefull to note which groove you put it in, because that dictates how many turns you crank it before it drops off the edge of the flywheel and hits full compression. We used to do three turns and then Bang, Bang, BAng…………

12 bore blank cartridge starting was reserved for showing off to friends, my dad did this once and forgot to remove the plastic bucket that kept rain water out of the exhaust chimmney. It flew about 20 feet in the air and came back down and landed perfectly over his head, I wished I had a camera handy that day !!

It was quite easy to accidentally start the two stroke engine backwards if it kicked back, you then had one forward and three reverse gears. Our Fowler VF crawler was almost the same, but that did run the opposite way to the Field Marshall engine.

Phil

Edited By Phil P on 19/06/2020 10:18:46

[Author]

Posts