Phosphine/ firestone

[edith]

This is a re-posting- cos I can't find the original- of the phosphine/ firestone sample article I did a couple of months ago. I thought that as the debate appears to have got round to firestone again I'd post it for people's reference. ps, I know the book is old but wikkipedia isn't and the properties of a substance don't change cos its 60 years later!

Phosphine/ Firestone

Phosphine, the gas produced when dragons chew firestone was first introduced in the very first Dragon-rider story Weyrsearch, published in 1967 which was later incorporated into Dragonflight (published 1968). It has appeared in nearly all the dragon-rider books since then.
The first time phosphine is mentioned by name, although “phosphoric air” (Dragonflight: pg 8, Rapp and Whiting 1969; pg 16, Corgi 1981) is mentioned, is in a description of how L’tol became dragonless.

“An ill-timed swerve during the Spring Games had brought L’tol and his beast into the full blast of a phosphine emission from S’lel’s bronze Tuenth.” (Dragonflight, pg 17, Rapp and Whiting 1969; pg 22, Corgi 1981).

The passage goes on to say that L’tol’s dragon died of phosphine poisoning.

So, what is phosphine, and why is such a poisonous gas a good choice for the fuel for the Pernese dragons’ fire?

Phosphine (PH3) is a hydride of phosphorous; it is a colourless, odourless gas in its pure form, although more usually it has a fishy odour (the firestone stench which is often mentioned in the books) due to the presence of substituted phosphine and diphosphine (P2H4). It is the common name of phosphorous hydride and is also known as phosphane and phosphamine.
Phosphine can be safely mixed without ignition with pure oxygen unless there is a sudden reduction in pressure, when it explodes. (Which explains why dragons don’t blow up, as the phosphine in the stomach must be at a greater or equal pressure to the atmospheric pressure.)
The gas reacts with oxygen when it ignites and produces phosphoric anhydride and water.

2PH3 + 4O2 = P2O5 + 3H2O

Phosphine is obtained in several ways, though the most relevant method in this case is by the hydrolysis of a metal phosphide such as calcium phosphide (Ca3P2).

CaP2 + 6H2O = 3Ca(OH)2 +2PH3

It is probably one of these metal phosphides that is the key ingredient in the firestone the dragons digest to produce phosphine.

However, phosphine is highly toxic and although only one character is mentioned as dying of phosphine, even a relatively small dose is fatal. However, there is one reprieve for the Pernese, it is possible to build up a resistance to it, as has been shown by the high level of resistance developed by pests in Asia and Australia, so, as, especially in a pass the average Pernese is liable to be exposed to a very low level of phosphine, all is not lost.


References

A Higher School Certificate Inorganic Chemistry (second edition), Adlam and Price, London October 1940.

wikipedia http://en.wikipedia.org/wiki/Phosphine

[P'ter]

I'm intrigued by the bit about passing phosphine through hydrochloric acid (and formaldehyde) to produce flame retardants.

Perhaps dragons don't blow up because stomach acids (if I remember right [and I'm not spending time at this time of night checking]) are hydrochloric.

[Brenda]

I always assumed that phosphine poisoning was one of those DF bloopers. The actual flames seemed more likely to me as the cause of his death.

[granath]

Originally Posted by Brenda

I always assumed that phosphine poisoning was one of those DF bloopers. The actual flames seemed more likely to me as the cause of his death.

People rarely die from being burned, unless a sizable proportion of their entire skin is charred. Mostly, fire deaths are caused by asphyxiation or smoke poisoning. Dragons are huge animals, meaning that they have a lot of volume compared to the surface area of their skin, not counting the wings. This would mean that it'd take a lot of flame to kill a dragon by cooking it, and even Canth, who had most of his skin partly sandblasted off by the trip to the Red Star, seemed none the worse once his oxygen deprivation wore off.

No, I think in this instance Anne did get the science right, phosphine killed Larth.

[edith]

that made more sense to me than the burning bit too.
Anne does get the science right more often than it seems, and possibly more often than she realises! There are very few actual blooper bloopers,. just a few things that don't quite make common sense rather than scientific sense.

[Brenda]

I thought Larth fell when his wings got crisped in mid-air. Falling would contribute quite a bit toward his death.

[granath]

There's no mention of his wings getting crisped in DF. It's been so long since I read MHoP that I can't remember the details there.

[AnnMarie]

Nope, no mention of Larth falling. Considering Lytol's face got hit, I always assumed Larth also caught the blast in the face...and it would make sense, if the muzzle caught the brunt, that phosphine posioning would occure.

[edith]

just been reading Dragon's fire and I can identify the wrong firestone. I can't jump to a quote after only one reading but it was described as yellow crystals, which means it is most likely to be.... aluminium phosphide.
I found 1 picture!

http://www.luxan.com/other_countries...cellaneous.htm

[Amaterasu]

Originally Posted by edith

It is probably one of these metal phosphides that is the key ingredient in the firestone the dragons digest to produce phosphine.

I have independently searched everywhere the information about firestone and agree that the phosphine can be produced from phosphides (that's the most reasonable way). However, as was mentioned before, metal phosphides are unstable in the presence of water. As a consequence, they cannot exist as minerals on a earth-like planet.
The only possible phosphor-containing minerals on Earth are phosphates and most probably the firestone is some kind of phosphate. The problem now is how phosphates could be reduced to phosphides in dragonstomach?

[StevenB]

Could fire stones be like geodes and have a waterproof shell with a phosphide core trapped inside? The phosphide could be released by breaking open the stones by chewing them. Perhaps the phosphides are ancient deposits from a geological (sorry, pernological) time when Pern was much drier?

[Cheryl]

That'd be quite dangerous to mine then, I would think, for the miners not to break any open.

And generally for geode collecting, while some are collected by pickaxing them out of the host rock, the majority are found lose at the base of the exposed rock, having been eroded out. Which is to say that it's hard work to get geodes lose and easier to let nature do it...but that takes years and years...as

[edith]

found it!

Apatite looks like the crystal in question, which is a source of calcium phosphate which reacts with water or acid to produce Phosphine gas.

Wikipedia

webmineral

It's also safer- this site sells it as a gem for jewellry.

[ghost8772]

Originally Posted by edith

found it!

Apatite looks like the crystal in question, which is a source of calcium phosphate which reacts with water or acid to produce Phosphine gas.

Wikipedia

webmineral

It's also safer- this site sells it as a gem for jewellry.

coming up with a plot hole with that. the pebbles of firestone that fire-lizards chewed couldn't exist. rainfall would leech the firestone of phosphine gas.

[edith]

Erm... Apatite wouldn't leak phosphine. It doesn't react with water but with acid.

so it would go...

firestone chewed

moves to stomach

reacts in stomach to produce calcium phosphate and other stuff (I'm busy trying to sort out the disaster that is sorting out documents atm so I can't sort out other products)

Calcium phosphate reacts with remaining stomach acid to produce phosphine

which when it is exhaled (change in pressure) and mixed with oxygen, combusts.

[ghost8772]

I hadn't looked it up mayself, just went off your previous post.

Originally Posted by edith

found it!

Apatite looks like the crystal in question, which is a source of calcium phosphate which reacts with water or acid to produce Phosphine gas.

Wikipedia

webmineral

It's also safer- this site sells it as a gem for jewellry.

it not reacting to water in the same way as an acid would be good then.

[edith]

bad typing on my part then- sorry

[Hans]

Is it reasonable to think that apatite is available in the (huge) quantities needed on Pern?

[edith]

I think it is very common.

[Hans]

Is that an answer to my question? *looks puzzled*

[Pernaficionado]

Yay!! That is cool! JTV, by the way, is like THE most awesome place to buy jewelry from. I strongly encourage ppl to look around its site. And I would think so, in the info section of the above wevlink it mentions its various uses and something is their about it being really important in fertilizers and the prescription industry. I would think then that there should be plenty for dragons since the pernese don't have those sort of industries.......yet.

[edith]

Originally Posted by Hans

Is that an answer to my question? *looks puzzled*

yep! It should be common enough.

[Hans]

OK, thanks, Edith! (Great work btw)

[GHarris]

Originally Posted by Pernaficionado

Yay!! That is cool! JTV, by the way, is like THE most awesome place to buy jewelry from. I strongly encourage ppl to look around its site. And I would think so, in the info section of the above wevlink it mentions its various uses and something is their about it being really important in fertilizers and the prescription industry. I would think then that there should be plenty for dragons since the pernese don't have those sort of industries.......yet.

And mineral grade / specimen grade apatite is a lot more common that gemmy or facet grade apatite.

GH

[CuriousFlit]

So apatite is normal firestone, and aluminium phosphide is the exploding flamestone? Cool! Awesome job with the research!

[CuriousFlit]

I found our copy of Dragonsfire. It says normal firestone looks like sandstone, but with blue-green crystals in it (the stuff they found on the beach anyway).

[GinnyStar]

Originally Posted by CuriousFlit

I found our copy of Dragonsfire. It says normal firestone looks like sandstone, but with blue-green crystals in it (the stuff they found on the beach anyway).

They also found in the High Reaches Weyr, starting of Fire Hold, Second Interval/Third Pass.

And the firestone is mined in Crom, for Jaxom got his from the mine there for MasterMiner was asking about it. In The White Dragon.

Was looking for this

[CuriousFlit]

Originally Posted by GinnyStar

They also found in the High Reaches Weyr, starting of Fire Hold, Second Interval/Third Pass.

And the firestone is mined in Crom, for Jaxom got his from the mine there for MasterMiner was asking about it. In The White Dragon.

Thanks!

Was looking for this

No problem. Oh, that reminds me, I found another plant for the Pern list:

creosote bush

Dragons Fire: https://books.google.com/books?id=Kl...20bush&f=false

https://en.wikipedia.org/wiki/Larrea_tridentata

Found some more info about Thread too: "A single Thread burrow could suck the life out of a whole valley in half a day."

https://books.google.com/books?id=Kl...burrow&f=false

[Brenda]

It would have to be very hard sandstone to be finding chunks of it on the beach. Sandstone usually erodes down to plain old sand very quickly.

[CuriousFlit]

Originally Posted by Brenda

It would have to be very hard sandstone to be finding chunks of it on the beach. Sandstone usually erodes down to plain old sand very quickly.

That could explain how the firelizards keep finding plenty of small enough pieces to eat.