Explosives

[Royfellows]

My friend and associate Ioan Lord has just uploaded his latest "Lost Mines" video. He has reopened a trial level that has been undisturbed for about 140 years, and found remains of Nobel explosives. I uploaded a comment which I feel worthy of reproducing here.

The first nitroglycerine based explosives were introduced into mining about 1870. However there was an issue with the nitro leaching out, particularly in sub zero temperatures as would occur in winter on the surface. I think, and this is my opinion, that this is the reason for underground explosives stores, not so much security. Later explosives has ingredients to prevent this, thus commonly occurring remaining explosives sometimes found underground will have the label "Polar Ammon Gelignite". The polar being indication of its resistance to this issue. This obviously is a dating feature indicating after the turn of the 20th century. Regardless of this, they will have a limited life span, so anything found underground will be completely inert anyway. More recently, explosives boxes may be found labelled "Antifrost Ammonium Gelignite". I rather think that this will answer a lot of questions. One sometimes finds cartridges made up in old newspapers. These are not explosive, but stemming cartridges made up with rock dust. This later fact was the source of some rumour about a certain mine in the Gwydir Forest.

 

[Mr. C]

You've sort of muddled two different problems a bit here. N.G. will leach out of most explosives that are nitro-glycerine based and is a separate problem to freezing. Of course, the now liquid N.G. is highly unstable regardless of temperature - as Alfred Nobles brother found out! The absorption into diatomaceous earth (as in "dynamite") reduces the sensitivity of the NG, compared to its unabsorbed state. It this form that constituted the early "dynamites".
The increase in sensitivity due to freezing is somewhat different, in that it affects NG when it is in it's absorbed state, as well as its liquid form. Frozen cartridges of NG "dynamite" etc. are highly unstable regardless of whether leeching has occurred.
To get round this, the N.G. was later mixed with ethylene glycol dinitrate (EGDN). This is made in a similar fashion the N.G. but instead of nitrating glycerine, ethylene glycol is used instead. This is of course "anti-freeze" and the resultant explosive freezes at a much lower temperature than N.G. So the N.G./EGDN mix also has a much lower freezing point. A similar mix is also used in the production of gelignites, as otherwise they are similarly affected.

 

[Royfellows]

Thanks for this. I did suspect the addition of Ethylene Glycol. My information re the other was from what I considered a reliable source, but I supose it is easy to confuse things.
Thanks again, its useful info.

 

[cantclimbtom]

I was told (but don't know if true) that EGDN was significantly cheaper to produce than NG. Probably not the ingredients as much as the process, I assume EGDN production isn't "safe" but surely has to be less hazardous than NG production.

Sadly I don't know anything of ICI/Cooke's (was at Penrhyndeudraeth and presumably you've seen those amazing photos of Croesor ). But I have seen info about the old NG plant at Enfield seen the infamous 1 legged stool. (A stool for production workers to sit on which had a single leg which was hinged at the floor so if you fall asleep you fall over.. and a bell rings so everyone knows you fell asleep and fell off), and details such as the production building was long and thin and on a slope, so gravity was used in the plant no pumps. The finished product was output onto a pond of water (outdoors, open air) where it'd float on the surface and it could be gently tapped off.

Hopefully EGDN production can't be as hazardous as that?? , the NG production was about to blow up at any moment when in use apparently (and told it did on 2 occasions). Noted that Cooke's wasn't immune from accidents though. https://en.wikipedia.org/wiki/Gwaith_Powdwr

A bit tangential, but a look round https://www.royalgunpowdermills.com/ is recommended if you're in the area, but not sure that you should travel big distance to see it though

 

[Mr. C]

I was told (but don't know if true) that EGDN was significantly cheaper to produce than NG. Probably not the ingredients as much as the process, I assume EGDN production isn't "safe" but surely has to be less hazardous than NG production.

Sadly I don't know anything of ICI/Cooke's (was at Penrhyndeudraeth and presumably you've seen those amazing photos of Croesor ). But I have seen info about the old NG plant at Enfield seen the infamous 1 legged stool. (A stool for production workers to sit on which had a single leg which was hinged at the floor so if you fall asleep you fall over.. and a bell rings so everyone knows you fell asleep and fell off), and details such as the production building was long and thin and on a slope, so gravity was used in the plant no pumps. The finished product was output onto a pond of water (outdoors, open air) where it'd float on the surface and it could be gently tapped off.

Hopefully EGDN production can't be as hazardous as that?? , the NG production was about to blow up at any moment when in use apparently (and told it did on 2 occasions). Noted that Cooke's wasn't immune from accidents though. https://en.wikipedia.org/wiki/Gwaith_Powdwr

A bit tangential, but a look round https://www.royalgunpowdermills.com/ is recommended if you're in the area, but not sure that you should travel big distance to see it though

The nitration of EGDN is virtually the same as NG and in fact the same vessels can be used for both processes. Therefore I cannot see why it should be any less hazardous than with NG. The reason for price difference is probably due to the fact that the separation and washing process is easier for EGDN and also difference in raw material cost.
Impact and friction sensitivity is the same for both, so similar handling hazards for both, when in liquid state.
EGDN has a lower density and lower VOD* than NG, so has lower brisance (shattering effect from the detonation front). It's also much more volatile - about 150 times that of NG, which limits it's use in higher temperature applications like propellants.
(data was obtained from "Explosives" Kohler & Meyer 4th ed and various old ICI Nobel date sheets in my possesion)
*VOD is velocity of detonation.

 

[cantclimbtom]

I suppose the difference, if it existed? would be the size of the "gap" between the temperature/energy needed to make it versus the temperature/energy needed to trigger explosion. I gather for NG it's a very narrow margin . The idea of warming and stirring is alarming to say the least. Even if you were "lucky" and only made a tiny bit before it blew, the idea of being blasted in the face with broken glass and very warm conc. nitric acid is uninviting!

 

[TomFerry]

 

[Royfellows]

I have come back on this thread to recount an experience that others may find interesting.

When I was at school my interest was chemistry. And when I left school my first job was that of a works chemist at an electroplating factory.

Well, I had developed a sort of fascination with explosives, and my job was a bit like giving Guy Forks a box of matches.
The project was to produce some nitroglycerine in a test tube. I had a good idea, fortunately, of what I was doing, and understood the importance of keeping the nitration process cool. This was done by immersing the test tube in cold water during the nitration process. Unfortunately, there were failures. I would watch the process closely and at the slightest sign of brown fumes and the mixture turning brown would swamp it with cold water and flush it away.

Anyway, I did eventually produce some nitro and proudly displayed my prize to my friends at the factory. Someone remarked that if it was nitro then just pouring a spot onto the floor should produce a bang. I tried this and nothing happened. Then someone suggested hitting it with a hammer. The resulting detonation was incredible, our ears were ringing for ages. The consensus was to get rid of the remainder in the test tube as quickly as possible.