Pickle Strength

[ericcee]

Yes, Noddy - that was the steelworks! (Consett Iron Company, for those who don't know what we are talking about.)
While I was still working there, I had a pale blue Austin 1100 (nice car, IMHO) which turned a strange shade of purple below the waist-line from all the iron ore mud and dust. Took a lot of elbow-grease with T-Cut to get it back to somewhere near the original colour.
Then there were the air-pump equipped 9F's storming up the bank with trains of iron ore hoppers, to come to a panting rest at the discharge gantry ... Happy days!
It's hard to believe anything like this existed there now.

And did you know that there's a lap-dancing club soon to open on Front Street?
My father and grandfather will be spinning in their graves!

[Noddy]

myfordmatt said:

keithanderson said:

Apparently one of the first to put sulphuric acid onto fluorspar (calcium fluoride) and make HF, was a Frenchman who habitually tasted all that he made (his name escapes me after 25+ years), like many of the other pioneers in the study of fluorides, he was dead within the year.

Good grief, how did he survive his first day in a lab, let alone have a career?

His Career was before he found fluorides, even with heavy metals such as lead so long as you don't indulge too often, you can get away with it.

lead was used to treat vinegary wine (lead acetate apparently tastes like sugar, I've not tried it, but apparently in adults, and in small infrequent amounts, so that it does not accumulate ( i don't know the half life in your body) small amounts of lead is not supposed to do lasting damage)

Just a thought, if he was Scots instead of French, would he have deep fried it b4 tasting it?

[Noddy]

Ericee,
There are plenty of my ancestors in the cemetry at Blackhill and the fields downwind of Mountjoy who will be spinning too!

A sad fate for the Town that had the first Sally Army band in the World, and where all musicals got their first trial run (it was the most cosmopolitan town available). My ancestors were there at the start, as blast furnace men and the name died out (I'm related down the female line) in 1980...

I've still got happy memories of the steam shunters at Dewent haugh up to '76. It was the highlight of a childhood trip to whitleybay.

My Granny liked the smell of the cokeworks as it reminded her of her father. Her Maternal Grandfather came to Consett to set up the company Brass band, and was too niaive to ask for a job as well, so he ended up a pit yakka....

Better get some of my own work done before I end up likewise

Take care

[Tony K]

So, to sum up then, providing we do not use hydrofluoric acid as a cleansing agent, the only place we are likely to come across hydrofluoric acid in model engineering is when viton o rings (used in cylinders and sight glass seals etc.) suffer burning. In this case we should be very careful, remove the debris with tweezers and wash everything off, possibly using HF antedote gel as a precaution.

Maybe we should avoid viton and use another material which may have slightly inferior temperature performance and longevity, but avoid the hazard completely?

Have I got it right?

Regards, Tony.

[Noddy]

Fluorocarbon plastics e.g. PTFE (Teflon) are the things not to burn.

Not to set another hare running, but.... the "halon" fire extinguishers give off phosgene when they hit something hot, but just touching that won't cost you a finger.

[Boadicea]

Fluorocarbon plastics e.g. PTFE (Teflon) are the things not to burn.

So are you saying there is not a problem with viton?
Can someone give us clarity here. Dredging up all the hazards in the world is not helpful. I would like to get it right and in proportion. Can someone answer his question

Have I got it right?

Regards, Tony.

.... or possibly re-phrase it?

Thanks, Bo

[Noddy]

ouch!

en.wikipedia.org/wiki/Viton

This lists the polymers used in Viton. Apparently you are looking at 60 to 70 % F in the polymers, so yes, overheating them will almost certainly give HF, as will other plastics containing Fluorine, They tend to be the more heat resistant ones (don't ask me what all of them are, I don't know, but someone out there will)
hope this is more helpful.

[Noddy]

Here is the link to the toxicology:

en.wikipedia.org/wiki/Hydrofluoric_acid

[havoc]

the "halon" fire extinguishers give off phosgene when they hit something hot, but just touching that won't cost you a finger.

Same for the old freons. Don't smoke!

[S.D.L.]

So are you saying there is not a problem with viton?
Can someone give us clarity here. Dredging up all the hazards in the world is not helpful. I would like to get it right and in proportion. Can someone answer his question

Have I got it right?

Regards, Tony.

At work we have stopped using Viton for O-rings in any position where they can overheat. If a customer insists on viton i send them a copy of the data sheet from walkers and most dont want to use them in that situation any more. I believe some model engineer lost a finger in Australia fron a decomposed viton O-ring which was what made me check it out at work.

Steve Larner

[jackrae]

Noddy

Not so sure about halon changing to phosgene but he old carbon tetrachloride contents certainly did change to phosgene in contact with flame / hot surfaces.

I once poured some (in the days when you could pop into Boots and buy it by the gallon - along with benzene !!) on a pile of burning shavings in my father's shed and was "amazed" how it suddenly turned the air "bad". It certainly put the fire out and almost me as well.

Halon was used extensively offshore in the oil industry until fairly recently, on the basis that it was completely safe - apart from doing untold damage to the atmosphere. On the basis of the latter concern it has now been replaced by either water mist, CO2 or inergen.

[Noddy]

I know it is no excuse for spinning off on tangents, but the halogenated hydrocarbons (ones with Fluorine, chlorine, bromine etc bonded into them) all seem to do dodgy things when they get hot. I know we are coming away from the subject of pickles a bit, but the halogenated de greasing solvents can be sods.

Asphalt labs used to (and probably still do) use methylene chloride for disolving bituminous binders. flames and incandescent surfaces were not allowed and Smoking in the labs is a sacking offence. An old colleague, now in the big lab in the sky, used to tell of a workmate who had stayed on late one night. his body was found in the morning with a burned out cigarette butt.

I can not vouch for the authenticity, but have heard that when phosgene was used in WW1, it did not cause the same alarm as burning and choking clouds of chlorine had.

Instead it was supposed to smell of new mown hay!


I should already have said that methylene chloride is also used a glue for plastics and rubbers as well as dodgy chlorinated compounds showing up in solvents, thinners, paints and lacquers (paint on and spray on) and the classic - as dry cleaning and de greasing agents.

After following the referenced link in wikipedia about HF turning up in car washing chemicals, perhaps the nanny state may have some slight uses after all...

- well, ok, perhaps not

Perhaps the least we can expect of overheating halogenated compounds is the liberation of the acids (HF, HCl...), after that, exactly which are the most dangerous, I do not know, but we are looking at phosgene, and a range of "dioxins", which accumulate in body fat and cell membranes.

as for nitrogen tri-chloride and nitrogen tri-iodide, that is the story of a miss spent youth and damaged ear drums..

[alanstepney]

Talking of assorted chemicals, there was a time when, to clean the bench (or anything else) we would pour a load of trichloethelyne on it and swab with cloth.
Could buy the stuff by the gallon easily back then.

Ahh well, dont suppose you could, or would want to, now.