35 replies to this topic

[jcow]

i know this might be taboo on ukrocketry, but i might attempt to make n*trocellul0se with the NaNO3, by dissolving it in concentrated H2SO4 to create a nitrating solution
( http://www.powerlabs...rocellulose.htm ). i reckon that semi-nitrated cotton sewing thread could be useful for a very fast fuse. i would also like to make some NC laquer. i assume that, the fire retardant should'nt affect the finished NC hugely. dont worry, im not intending to make the h*xanitrate.

sorry if this is classified as h1gh e*plosive. i personally dont think cellulose trinitrate is.

[damocov]

I'd advise against using nitrocellulose as a "fast" fuse as it's more likely to be an "instant" fuse (they don't call it flash cotton for nothing)

I use flash cotton, flash paper and flash string when performing, and you need to be careful with the stuff.

As an idea of the time, my fireball launcher (homemade - I'll post pics if anyone's interested) uses 1 inch length of string to take the fire from the flint pan through to the launcher tube, this takes about 1-2a seconds from striking to seeing the fireball burst 6 foot in front of me so the string takes about 1/2 second to burn through.

If you light a 20cm length of nitrocellulose string un confined in air then it burns almost instantly.

If you don't want to make blackmatch then try touch paper which is definatley slower than NC string!

[jcow]

I've just made some NC with cotton wool. As im still not sure whether the NaNO3 has fire redartant or if its just me, i dont know if it'll work. Its still drying at the moment. I used filtered, concentrated battery acid for the H2SO4 and allowed the cotton to nitrate for 15mins. Even if it only burns slightly faster than normal cotton, its still a start.

Edited by jcow, 22 March 2006 - 07:09 PM.

[jcow]

the NC didnt work, but i made some succesful black powder. i found out that the BP has to be ground into a very fine dust to work, and i spent ages getting the proportions correct. it now burns quickly and does'nt leave any white residue (the unused sodium nitrate, i didnt have enough carbon in the mixture).there was way too much NaNO3 in the mixture when i used bigG's 72:17:11 recipe. i am still trying to perfect the BP, and i will post the recipe for it when i have done it.

[damocov]

Just re-read your post above and I have a query, How are you making your nitrating mixture using NaNo3?

Usually I'd expect to use HNO3/H2SO4 for a nitrating mixture.

If I rememebr correctly (and it's been a few years since I sat in a lecture theartre) the equlibrium of

HNO3 <-> NO2+ + NO3- + H2O

Naturally sits towards the left, but with the dehydrating power of the H2SO4 reducing the H2O content the equilibrium is shifted towards the right (Le Chateliers principle) thus giving you the nitronium ion to substitute for your OH- .

Now with NAN03 I can't see how you'd acheive the same strength of effect as there is no obvious way of liberating water for the H2SO4 to dehydrate to shift the equilibrium.

2NaNo3 + H2SO4 ---> Na2SO4 + H2O + NO3- + NO2+ Maybe???

Though I'd have thought NaHSO4 and HNO3 would have been more stable products.

If anyone can explain how it works I'd appreciate it - my brains hurting a bit !

[Stuart]

God it's been a long time since I looked at nitrations. From what I remember from school and read, Nitric acid would be formed in situ

H2SO4 + NO3(-) <--> HSO4(-) + HNO3

The rest you probably know and can work out. Apparently, this isn't meant to be a very good way of forming the Nitration ion. I'm sure theres more to it than that, but I cant remember. Wish I has kept all my Chemistry notes

[jcow]

i am not too sure, as i am a young 'chemist'. powerlabs explains the process, http://www.powerlabs...rocellulose.htm .
i have only got a small amount of 1 molar nitric acid, so i decided to try the NaNO3 + H2SO4 nitrating solution. i assume that using this method, sodium sulphate and other salts will be present in the solution as well as a mix of sulphuric and nitric acid, i tried, and failed, but i think my H2SO4 was'nt concentrated enough. i did'nt want to risk inhaling sulphur trioxide fumes. the battery acid is approximately 33% H2SO4, so i boiled it down to a third of its original volume.the battery acid probably had lead salts dissolved in it, which would also have affected the NC. powerlabs claims that you use 1 gram of KNO3/NaNO3 for every 3.325 grams of 98% conc. H2SO4. i left the cotton to nitrate for over ten Minutes.

i hoped that i would at least notice a slight improvement in burn rate, compared to normal cotton, but my 'Nitrocellulose' which i thought was dry didnt even burn! i suppose i rushed the experiment and didnt powder the NaNO3 properly or concentrate the acid enough.i also think i used to much cotton. i'll try this again, when i have some proper pyrex jars (jar i used to concentrate the acid cracked on my second attempt!).

as stuart said, the proper way its to heat the solution and bubble the nitrogen dioxide produced through water to make nitric acid.the problem is that NO2 is highly toxic and i dont have a retort.

Edited by jcow, 23 March 2006 - 11:17 PM.

[Stuart]

The trouble with using a Nitrate salt is, that concentrated Sulphuric acid becomes vital. Nitric acid on its own will nitrate things (although slowly).

2HNO3 <--> NO2(+) + NO3(-) + H2O

This is when you really do need concentrated Sulphuric acid, because it will help shift the equilibrium to the right. Due to the amount of water in the Sulphuric acid you used, you will probably find that a lot of the Nitric acid that was made in situ, will just sit there moving back and forth between HNO3 and NO3(-). Because water is formed when HNO3 breaks up, the equilibrium will want to shift back to the left.

This is why nitrating with Sulphuric acid and a Nitrate salt needs very strong Sulphuric acid. The reaction is already slowed because of the NO3(-) thats formed from the salt and the NO3(-) from the HNO3. The equilibrium already wants to go to the left. Then, on top, you need lots of Sulphuric acid to get rid of the water which will push it left even more if left unattended.

It might be possible to nitrate cotton a bit with the mixture you had, but it would need much longer than 10 minutes.

It's all flooding back to me now, Le Chatelier would be proud.

[jcow]

thanks for the advice. thinking about it, distilled water is added to the battery acid, diluting it. next time i will boil it down until the sulhurous fumes are produced (i know this is dangerous, but it is done outside!). after three evenings of testing and and pestle and mortaring, i am pretty sure the sodium nitrate is quite pure. i'm hoping to get a retort off ebay so i can make nitric acid, and make a proper nitrating solution.

[fishy1]

i suppose i rushed the experiment and didnt powder the NaNO3 properly or concentrate the acid enough.

The NaNO3 doesn't need to be powdered as it dissolves. This should save you some time.

[Phoenix]

I've used sodium nitrate to make yellow stars in the summer (in the UK). I found they'd dry OK on a warm day, and then stay dry so long as they were kept in a sealed container and not left out. They seemed OK in fireworks that were used within a few days of construction, and kept dry prior to that. However, in the winter, the same stars will melt into paste if left outside their container.

The burning of unconfined sodium nitrate compositions such as stars, lances and loose powder (the applications for which I have tried using it) is much slower than an equivalent potassium nitrate based composition. The star composition I settled on was pretty much black powder with the appropriate change of oxidiser, and was milled like BP. It still made pretty long burning stars.

[jcow]

I've used sodium nitrate to make yellow stars in the summer (in the UK). I found they'd dry OK on a warm day, and then stay dry so long as they were kept in a sealed container and not left out. They seemed OK in fireworks that were used within a few days of construction, and kept dry prior to that. However, in the winter, the same stars will melt into paste if left outside their container.

The burning of unconfined sodium nitrate compositions such as stars, lances and loose powder (the applications for which I have tried using it) is much slower than an equivalent potassium nitrate based composition. The star composition I settled on was pretty much black powder with the appropriate change of oxidiser, and was milled like BP. It still made pretty long burning stars.

i have the same problem, i finely powder my NaNO3 compositions, but none of them burn as fast as proper BP. i attempted to make a rocket today using the 'visser' miture 69:27:4 (NaNO3, C, S) but this had way to much oxidiser and left a large amount of residue. in the end, i added about another 10 parts charcoal and 4 parts sulphur and it just about burned properly.eventually i made a motor that actually moved off a 45 degree launch ramp. this was without a stick!. i'll try again tommorow with a lighter tube and without wet garden clay used as plugs.

I would say that a better sodium nitrate (garden direct) 'BP' would have the following proportions 55:35:10 (NaNO3,C,S)

[jcow]

I know this is going to sound very stupid! in general, are ratios for rocket propellants measured in volume or weight? i've always assumed that it is volume. maybe this is why im getting things wrong

[jcow]

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Edited by jcow, 28 March 2006 - 07:29 PM.

[Frozentech]

I know this is going to sound very stupid! in general, are ratios for rocket propellants measured in volume or weight? i've always assumed that it is volume. maybe this is why im getting things wrong

Always, in pyrotechnics, including rocket props, measurements are by *weight*.